JP3530748B2 - Power converter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for preventing DC bias magnetization of a transformer in a power converter connected to an AC line such as an AC power system or a load via a transformer.

[0002]

2. Description of the Related Art FIG. 9 is a diagram showing a conventional power conversion device of this type disclosed in, for example, Japanese Unexamined Patent Publication No. 7-28534.

In FIG. 9, 1 is an AC power system, 2 is a self-exciting converter that generates an AC voltage based on a gate drive signal, and 3 is a single-phase connecting the AC power system 1 and the self-exciting converter 2. A transformer 4, a DC voltage source for supplying a DC voltage to the self-exciting converter 2, 5A and 5B, a current detector for detecting a current flowing through a winding of the transformer 3, and 6 are current detectors 5A and 5B. A subtractor that takes a difference, 7 is a DC component detector that detects a DC component from the output of the subtractor 6, 8 is a voltage detector that detects the voltage of the AC power system 1, and 9 is a set voltage of the AC power system 1. Voltage reference 10, 10 is a system voltage control means for creating a current command of the self-excited converter 2 according to the deviation between the voltage of the AC power system 1 and the voltage reference 9, 11 is a system voltage control means 10
Current control means for creating an output voltage command of the self-excited converter 2 in accordance with the deviation between the current command output by the current detector 5A and the output from the current detector 5A, and 12 indicates the output of the DC component detector 7 and the current control means 11. An adder for adding the output and 13 is an adder 12
Pulse width modulation (PWM) control circuit that determines the firing timing of the self-extinguishing type element of the self-exciting converter 2 according to the output of the above, and 14 amplifies the output of the pulse width modulation control circuit 13 It is a gate pulse amplification circuit that supplies a gate drive signal to the excitation converter 2.

Next, the operation of the conventional power converter shown in FIG. 9 will be described. In the power converter shown in FIG. 9, when the voltage of the AC power system 1 or the output voltage of the self-exciting converter 2 includes a DC component, an exciting current including the DC component flows in the transformer 3. However, the DC component of this exciting current causes the transformer 3 to be demagnetized, and as a result, the iron core of the transformer 3 is saturated.

When the iron core of the transformer 3 is saturated, the transformer iron core has the excitation characteristics shown in FIG. 10, so that a slight voltage change causes an abrupt increase in current, resulting in an overcurrent in the self-excited converter 2. It occurs and protection stops.

Of the winding current of the transformer 3, the current flowing in the winding connected to the AC power system 1 is used as the primary winding current, and the current flowing in the winding connected to the self-excited converter 2 is set to two. When the secondary winding current is used, the primary winding current of the transformer 3 detected by the current detector 5A and the secondary winding current of the transformer 3 detected by the current detector 5B are input, Since the exciting current of the transformer 3 is obtained by obtaining the difference by the subtractor 6, the direct current component included in the exciting current for demagnetizing the iron core of the transformer 3 is the direct current component for detecting the direct current component from the output of the subtractor 6. It is detected by the detector 7.

On the other hand, the system voltage control means 10 creates a current command to be output from the self-excited converter 2 so that the feedback value of the system voltage detected by the voltage detector 8 matches the voltage reference 9. The current control means 11 creates a voltage command to be output by the self-excited converter 2 so that the primary current of the transformer 3 detected by the current detector 5A matches the current command output by the system voltage control means 10. .

Transformer 3 detected by DC component detector 7
The DC component included in the exciting current of 1 is added by the voltage command of the power converter 2 created by the current control means 11 and the adder 12, and acts as a voltage command correction value of the self-exciting converter 2.

The pulse width modulation control circuit 13 creates a gate pulse width signal according to the output of the adder 12, and the gate pulse amplification circuit 14 ignites and extinguishes the semiconductor element of the self-excited converter 2 according to the gate pulse width signal. By creating a gate drive signal for arcing and applying this gate drive signal to the self-exciting converter 2, the self-exciting converter 2 switches the self-extinguishing type element according to the voltage of the DC voltage source 4 to cause the adder 12 to operate. Generates a voltage corresponding to the output.

As described above, in the conventional power converter shown in FIG. 9, the self-exciting converter 2 outputs the voltage corresponding to the output of the adder 12, so that the voltage of the AC power system 1 or the self-exciting system is used. When the output voltage of the converter 2 contains a DC component, the DC component contained in the exciting current of the transformer 3 is detected and given to the adder 12, so that the voltage of the AC power system 1 or the self-excited converter 2 The self-exciting converter 2 generates a voltage that cancels the DC component contained in the output voltage, and operates so as to avoid the DC bias magnetization of the transformer 3.

[0011]

Since the conventional power converter is constructed as described above, the subtractor 6 obtains the exciting current from the difference between the primary current and the secondary current of the transformer 3,
The direct-current component is extracted by the direct-current component detector 7 to adder 1
Since the voltage output from the self-exciting converter 2 is also a voltage proportional to the exciting current due to the fact that it is given to No. 2, the relationship between the magnetic flux of the iron core of the transformer 3 and the exciting current is non-linear as shown in FIG. Therefore, if a voltage proportional to the exciting current that rapidly increases near the saturation region is output by the self-exciting converter 2, there is a problem of overcompensation and instability.

Further, in the exciting current characteristics shown in FIG. 10, even in a region where saturation is not reached, especially in a region where the exciting current is small, the value is usually several percent or less of the rated current, and the accuracy of the current detectors 5A and 5B is improved. Considering this, there are problems such as erroneous detection due to noise, etc., and unstable operation due to erroneous detection of the exciting current DC component due to alias noise caused by the switching ripple of the self-excited converter 2 when the system is constructed with a digital control system. It was

Further, the relationship between the winding current and the phase current, the relationship between the phase voltage and the line voltage, etc., which should be considered when the transformer 3 and the self-excited converter 2 adopt the three-phase configuration, are considered. There was a problem that it did not exist.

The present invention has been made in order to solve the above problems, and it is possible to stably suppress the DC bias magnetization of a transformer without being affected by the nonlinear characteristics of the exciting current of the transformer. An object of the present invention is to obtain a power conversion device that can reliably suppress DC bias magnetization of a transformer even when a power conversion device or a three-phase configuration is adopted.

[0015]

An electric power converter according to the present invention is a power converter connected to an AC line via a transformer, and detects an excited state quantity for detecting an excited state quantity of the transformer. Means, a DC component detecting means for detecting a DC component of the output from the excitation state quantity detecting means, and a value obtained by adding the output to the voltage command value so that the output from the DC component detecting means becomes a predetermined target value. On the basis of the control means for controlling the output voltage of the power converter based on the above, it is inserted between the excitation state quantity detection means and the DC component detection means or between the DC component detection means and the control means. , The output is performed only when the input is less than or equal to the first set value or greater than or equal to the second set value greater than the first set value, and the input exceeds the first set value and the second set value is exceeded. Output when less than Those having a dead band means is not performed.

Further, the power converter according to the present invention is a power converter connected to an AC line via a transformer, and an exciting state quantity detecting means for detecting an exciting state quantity of the transformer, and this exciting state quantity detecting means. DC component detecting means for detecting a DC component of the output from the state quantity detecting means, and the power conversion based on a value obtained by adding the output to the voltage command value so that the output from the DC component detecting means becomes a predetermined target value. In a device provided with a control means for controlling the output voltage of the device, it is inserted between the excitation state quantity detection means and the direct current component detection means or between the direct current component detection means and the control means,
When the input is less than or equal to the first set value or more than or equal to the second set value greater than the first set value, the limiter means for performing the output with the input limited is provided.

Further, the exciting state quantity detecting means of the power converter according to the present invention is the first detecting means for detecting the primary side current of the transformer.
Current detector, second for detecting the secondary side current of the transformer
The current detector and the exciting current calculating means for calculating the exciting current of the transformer based on the output difference between the two current detectors, and the exciting current is output as the excited state quantity of the transformer.

Further, the excitation state quantity detecting means of the power conversion device according to the present invention detects the primary side voltage of the transformer.
Voltage detector, second for detecting the secondary voltage of the transformer
A voltage detector, and a magnetic flux amount calculating means for calculating the magnetic flux amount of the transformer based on the outputs of both the voltage detectors,
The amount of magnetic flux is output as the amount of excitation state of the transformer.

Further, the excitation state quantity detecting means of the power converter according to the present invention comprises a magnetic flux quantity detecting means for detecting the amount of magnetic flux flowing in the iron core of the transformer, and the magnetic flux quantity is used as the excitation state quantity of the transformer. It is what is output.

The power converter according to the present invention is a power converter connected to an AC line via a three-phase transformer, and is in an excited state for detecting the three-phase excited state quantity of the transformer. Quantity detecting means, DC component detecting means for detecting the DC component of the three-phase output from the excitation state quantity detecting means, and this DC
Make sure that the three-phase output from the component detection means reaches the specified target value.
Addition correction to the three-phase voltage command value with the correction value according to the output
Then, the power conversion is performed based on the corrected three-phase voltage command value.
Control means for controlling the output voltage of the device, and the direct current component
Minute detection means and the control means, the DC
Converts the three-phase output from the component detector to a three-phase voltage output
And a three-phase output from the phase voltage calculating means.
Add the phase voltage output to the above three-phase voltage command value as the above correction value.
To calculate.

The excitation state quantity detecting means of the power converter according to the present invention is the first current detecting means for detecting the primary side three-phase winding current of the transformer, and the secondary side three-phase winding of the transformer. A second current detecting means for detecting a line current and an exciting current calculating means for calculating a three-phase exciting current of the transformer based on an output difference between the both current detecting means are provided, and the three-phase exciting current is converted into the transformer. Is output as a three-phase excitation state quantity.

The excitation state quantity detecting means of the power converter according to the present invention is the first voltage detecting means for detecting the primary side three-phase voltage of the transformer, and the secondary side three-phase voltage of the transformer. Second voltage detecting means, and magnetic flux amount calculating means for calculating the three-phase magnetic flux amount of the transformer based on the outputs of both the voltage detecting means, and the three-phase magnetic flux amount for the three-phase excitation state of the transformer. It is output as a quantity.

Further, the excitation state quantity detecting means of the power converter according to the present invention comprises magnetic flux quantity detecting means for detecting a three-phase magnetic flux quantity flowing in the iron core of the transformer, and the three-phase magnetic flux quantity is detected by the transformer. It is output as a three-phase excitation state quantity.

Further, in the power converter according to the present invention, when the winding on the primary side or the secondary side of the transformer is star-connected to form the zero-phase current path, the excitation state quantity detecting means is: The zero-phase component is detected from the three-phase excitation state quantity, and the one obtained by subtracting the zero-phase component from the three-phase excitation state quantity is output.

Further, in the power converter according to the present invention, when the primary winding or the secondary winding of the transformer is delta connected, the current detecting means on the delta connected side is A phase current detector for detecting a phase current on the delta connected side, and a winding current calculating means for calculating the three-phase winding current of the delta connected winding from the output of the phase current detector Is.

Further, in the power converter according to the present invention, when the primary winding or the secondary winding of the transformer is delta-connected, the current detecting means on the delta-connected side is the above-mentioned one. A winding current detector is provided which is inserted into each winding on the delta connected side and detects the winding current of the three-phase winding.

Further, in the power converter according to the present invention, when the winding on the primary side or the secondary side of the transformer is star-connected to form the zero-phase current path, the side of the star-connected side of the transformer is connected. The current detection means includes a winding current detector that detects the winding current on the star-connected side, a zero-phase component detector that detects a zero-phase component of the output from the winding current detector, and the winding. It is provided with a subtractor that subtracts the zero-phase component from the output of the current detector and outputs a winding current of three phases.

Further, in the power converter according to the present invention, when the primary winding or the secondary winding of the transformer is delta-connected, the voltage detecting means on the delta-connected side is the above-mentioned one. A phase voltage detector for detecting the phase voltage on the delta connected side, and a winding voltage calculating means for calculating the three-phase winding voltage of the delta connected winding from the output of this phase voltage detector Is.

Further, in the power converter according to the present invention, when the primary winding or the secondary winding of the transformer is delta connected, the voltage detecting means on the delta connected side is It is provided with a winding voltage detector that detects the voltage of each winding on the delta connection side.

Further, in the power conversion device according to the present invention, when the primary winding or the secondary winding of the transformer is star-connected, the voltage detection means on the star-connected side is the above-mentioned. A line voltage detector that detects the line voltage on the star-connected side, and a winding voltage calculation means that calculates the three-phase winding voltage of the star-connected winding from the output of this line voltage detector. Be prepared.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below. Embodiment 1. 1 is a configuration diagram showing a configuration of a power conversion device according to a first embodiment of the present invention. In FIG. 1, 1 is an AC power system that is an AC line, 2 is a self-exciting type that is composed of a semiconductor element such as a GTO thyristor, a GCT thyristor, an IGBT, and a transistor that can be self-extinguished, and capable of AC / DC conversion based on a gate drive signal A converter 3 is a transformer that connects the AC power system 1 and the self-excited converter 2, 4 is a DC voltage source that supplies a DC voltage to the self-excited converter 2, and 5A and 5B are windings of the transformer 3. A current detector for detecting the flowing current, 6 is a current detector 5
A subtractor that takes the difference between A and 5B, 7 is a DC component detector that detects a DC component from the output of the subtractor 6, 8 is a voltage detector that detects the voltage of the AC power system 1, and 9 is an AC power system 1
Of the system voltage control means 10 for creating a current command of the self-excited converter 2 in accordance with the deviation between the voltage of the AC power system 1 and the voltage reference 9 and 11 of the system voltage control means 10. Current control means for creating an output voltage command of the self-excited converter 2 according to a deviation between the output current command and the output from the current detector 5A, and 12 is an output of the DC component detector 7 and an output of the current control means 11. And 13 are pulse width modulation (PWM) control circuits that determine the firing timing of the self-extinguishing type element of the self-exciting converter 2 according to the output of the adder 12 and create a gate pulse signal, and 14 is a pulse A gate pulse amplifier circuit that amplifies the output of the width modulation control circuit 13 and gives a gate drive signal to the self-excited converter 2, and 15 is a dead band means that outputs only when the input value is above a certain value or below a certain value.

FIG. 2 is a diagram showing the operating characteristics of the dead zone means 15. As shown in the figure, the dead zone means 15 is operated when the input is less than or equal to the first set value T1 or the second set value T2.
Output is performed only when (T2> T1) or more, that is, a dead zone in the range of set values T1 to T2 is provided. This set value T
As the absolute values of 1 and T2, the current detectors 5A and 5A which cause malfunctions when the dead zone means 15 is not provided.
The offset and noise of B, and the alias noise caused by the switching ripple of the self-excited converter 2 and the like are set to a level at which they can be removed.

Next, the operation will be described. Current detector 5
An excitation current component as an excitation state quantity in a subtractor 6 from the primary winding current of the transformer 3 detected in A and the secondary winding current of the transformer 3 detected in the current detector 5B. Ask for. The winding ratio of the primary winding and the secondary winding of the transformer 3 is 1
If not, multiply the coefficient 1 shown in (Equation 1) between the current detector 5A and the subtractor 6, or the coefficient 2 shown in (Equation 2) between the current detector 5B and the subtractor 6. The exciting current can be obtained by multiplying by. Coefficient 1 = primary winding winding number / secondary winding winding number (Equation 1) coefficient 2 = secondary winding winding number / primary winding winding number (Equation 2)

The output of the subtractor 6 includes the offset of the current detectors 5A and 5B, which causes the erroneous detection of the exciting current DC component, noise, alias noise caused by the switching ripple of the self-excited converter 2, and the like. Dead band means 1
Since it is possible to remove signals above a certain level and below a certain level by means of 5, it is possible to remove them.

FIG. 3 shows the operation of the dead zone means 15. FIG. 7A shows the exciting current of the transformer 3 obtained as the output of the subtractor 6, in which the transformer 3 is not biased and the outputs of the current detectors 5A and 5B are also offset. Indicates that there is no. The actual waveform of the exciting current is distorted due to the hysteresis characteristic of the iron core of the transformer 3 or the like.
It has a sine wave shape. Under the above conditions,
Since the exciting current of the transformer 3 does not include a direct current component, the output of the direct current component detector 7 becomes zero as shown in FIG. 3B, and the adder 12 outputs the output voltage command value from the current control means 11. Output as is.

Next, although the transformer 3 is not biased, if the output of the current detector 5A or 5B includes an offset, the output from the subtractor 6 becomes as shown in FIG. . In the figure, Δ is an offset amount. Therefore, in the conventional case where the dead zone means 15 does not exist, FIG.
The DC output from the DC component detector 7 shown in FIG. Therefore, although the transformer 3 is originally not biased, the DC voltage component is generated in the self-excited converter 2 based on the erroneous correction signal from the DC component detector 7, and the transformer 3 is turned on. Demagnetize.

On the other hand, in the case where the dead zone means 15 of the present invention is provided, as shown in FIG. 6 (e), the value obtained by adding the offset of the current detector 5A or 5B to the exciting current in the normal range is , The input falls within the dead zone of the dead zone means 15, and the output of the dead zone means 15 becomes zero ((f) in the figure). Therefore, as a matter of course, the output of the DC component detector 7 also becomes zero, and the self-excited converter 2 does not perform an unnecessary operation of generating a DC voltage component.

The exciting current from the subtractor 6 is applied to the dead zone means 1
A DC component detector 7 detects the DC component that is large beyond the dead zone of 5 and causes the transformer 3 to reach the biased magnetic saturation. The DC component detector 7 is a detector that extracts only the DC component from the AC signal including the DC component, and can be configured by, for example, a low-pass filter, an integrator, a moving average filter, or the like.

On the other hand, the system voltage control means 10 creates a current command to be output from the self-excited converter 2 so that the feedback value of the system voltage detected by the voltage detector 8 matches the voltage reference 9. The current control means 11 creates a voltage command to be output by the self-excited converter 2 so that the primary current of the transformer 3 detected by the current detector 5A matches the current command output by the system voltage control means 10. .

The DC component contained in the exciting current of the transformer 3 which is detected by the DC component detector 7 and exceeds the set value of the dead zone means 15 is the voltage of the power converter 2 created by the current control means 11. The command is added by the adder 12 and acts as a voltage command correction value for the self-excited converter 2, the pulse width modulation control circuit 13 creates a gate pulse width signal according to the output of the adder 12, and the gate pulse amplification circuit 14 By generating a gate drive signal for firing and extinguishing the semiconductor element of the self-excited converter 2 according to the gate pulse width signal, and giving this gate drive signal to the self-excited converter 2, the self-excited converter 2 Since the self-extinguishing element is switched according to the voltage of the DC voltage source 4 to generate a voltage corresponding to the output of the adder 12, that is, the output of the DC component detector 7 is set to a sufficiently low level. (Usually the zero level) it would be controlled to become so, the voltage output from the self-commutated converter 2 is always acts to suppress the magnetic deflection of the transformer 3.

Although the dead zone means 15 is provided between the adder 6 and the DC component detector 7 in FIG.
Between A and the subtractor 6 or between the current detector 5B and the subtractor 6
The same effect can be obtained even if it is provided between the DC component detector 7 and the DC component detector 7 and the adder 12. However, the dead zone means 1
It goes without saying that the set value needs to be changed appropriately depending on the insertion position of 5.

In the present embodiment, the method of obtaining the exciting current by multiplying the coefficient shown in (Equation 1) or (Equation 2) when the turns ratio of the transformer 3 is not 1 has been described. Also, the magnetomotive force obtained by multiplying the number of turns of the primary winding between 5A and the subtractor 6 and the number of turns of the secondary winding between the current detector 5B and the subtractor 6 may be obtained as the excitation state quantity. Since the amount is proportional to the exciting current, the same effect can be expected.

Further, in the present embodiment, the transformer 3 in which the excited state quantity of the transformer 3 is detected by the current detectors 5A and 5B.
Although the difference between the primary side current and the secondary side current is obtained by the subtractor 6 to obtain the exciting current, a voltage detector is used instead of the current detectors 5A and 5B and the output is integrated. Even if the excited state quantity is obtained based on the value, or the excited state quantity of the transformer 3 is directly obtained by providing a magnetic detector such as a Hall element or a search coil for detecting the magnetic flux quantity of the iron core of the transformer 3. The same effect can be obtained. That is, by obtaining the magnetic state quantities obtained respectively through the dead zone means 15 and adding them by the adder 12, it is possible to obtain an effect of preventing an unnecessary demagnetizing operation due to the offset of the current detector or the like.

As described above, in the power converter of the first embodiment shown in FIG. 1, the offset and noise included in the currents detected by the current detectors 5A and 5B cause erroneous detection of the exciting current DC component. , The dead zone means 1 for alias noise and the like caused by the switching ripple of the self-excited converter 2.
5, the output voltage DC component can be corrected correctly by obtaining the correct DC component without miscalculating the DC component of the excitation current of the transformer magnetic flux. It is possible to provide a highly reliable power conversion device that has an effect of suppressing magnetic bias, avoids protection stop due to overcurrent, and has high operation continuity.

Embodiment 2. FIG. 4 is a configuration diagram showing the configuration of the power conversion device according to the second embodiment of the present invention. The difference from FIG. 1 is that a limiter means 16 is provided instead of the dead zone means 15.

FIG. 5 is a diagram showing the operating characteristics of the limiter means 16. As shown in the figure, the limiter means 16 outputs with its input limited when the input is below the first set value T1 or above the second set value T2 (T2> T1). The absolute values of the set values T1 and T2 are determined in consideration of the saturation characteristics of the iron core of the transformer 3 from the viewpoint of preventing the output of the overcompensation voltage command correction due to the steep increase of the exciting current as the input.

Next, the operation will be described. Current detector 5
The operation of subtracting the current detected by A and 5B by the subtracter 6 to obtain the exciting current and extracting the DC component that causes the transformer 3 to reach the bias magnetic saturation by the DC component detector 7 is shown in FIG. It is similar to the power converter of the first embodiment.

As described in the prior art, the output of the DC component detector 7 is directly used as the voltage command correction value in the adder 1
When output via 2, the relationship between the excitation current and the magnetic flux of the iron core of the transformer 3 is a non-linear relationship as shown in FIG. When the exciting current increases and the DC component of the exciting current is output as it is as the voltage command correction value, a correction voltage more than necessary is output, which may cause instability.

However, in this embodiment, by limiting the maximum value and the minimum value of the output of the DC component detector 7 via the limiter means 16, the nonlinear relationship of the transformer core shown in FIG. 10 is obtained. Accordingly, an appropriate voltage command correction value is output without outputting an excessively large voltage command correction value. The output of the limiter means 16 is the adder 1
It is added in 2 and acts as a voltage command correction value as in the first embodiment.

In this embodiment, the limiter means 16
Is provided between the DC component detector 7 and the adder 12, but as in the case of the first embodiment, between the current detector 5A and the subtractor 6 or between the current detector 5B and the subtractor 6. The same effect can be obtained even if it is provided between the subtractor 6 and the DC component detector 7.

Similarly to the first embodiment, the method of multiplying the coefficient shown in (Equation 1) or (Equation 2) to obtain the exciting current when the turns ratio of the transformer 3 is not 1 has been described.
The magnetomotive force obtained by multiplying the number of turns of the primary winding between the current detector 5A and the subtractor 6 and the number of turns of the secondary winding between the current detector 5B and the subtractor 6 is obtained as the excited state quantity. However, since the amount is proportional to the exciting current, the same effect can be expected.

As in the first embodiment, the difference between the primary side current and the secondary side current of the transformer 3 detected by the current detectors 5A and 5B is subtracted from the excitation state quantity of the transformer 3. 6 is obtained by obtaining the exciting current, but a voltage detector is used instead of the current detectors 5A and 5B, and the excitation state quantity is obtained based on the integrated value of the output, or the transformer 3 The same effect can be obtained by directly providing the magnetized state quantity of the transformer 3 by providing a magnetic detector such as a Hall element or a search coil for detecting the magnetic flux quantity of the iron core. That is, the magnetic state quantities obtained respectively are taken out via the limiter means 16 and added by the adder 12, thereby eliminating the problem of outputting an unnecessary correction voltage due to the saturation characteristics of the transformer core.

As described above, in the power converter of the second embodiment shown in FIG. 4, the limiter means 16 is provided to limit the maximum value and the minimum value of the voltage command correction value, so that the transformer core Even if the exciting current increases rapidly near the saturation region, it is possible to correct the voltage command value correction by limiting an excessive voltage command correction value that is more than necessary. It is possible to obtain the effect of suppressing the DC bias magnetism of the device, avoid a protection stop due to overcurrent, and provide a highly reliable power conversion device with high operation continuity.

Embodiment 3. FIG. 6 is a configuration diagram showing a configuration of a power conversion device according to a third embodiment of the present invention. In FIG. 6, 3 is a transformer having a star winding primary winding and a delta connection secondary winding, 51A to 51C are current detectors for detecting the primary side three-phase current of the transformer 3, and 52A. 52C is a current detector that detects a secondary side three-phase current of the transformer 3, and 61A to 61C are windings of the transformer 3 from the secondary side three-phase current of the transformer 3 detected by the current detectors 52A to 52C. Subtractors 171A to 171C that perform subtraction for calculating the line current are subtractors 61A to 61C.
, A multiplier for calculating the winding current of the transformer 3 by a constant, 62A to 62C are the primary side three-phase currents of the transformer 3 detected by the current detectors 51A to 51C, and the multipliers 171A to 1C.
Subtractors 62A to 62C are subtracters 62A to 62C for subtracting the secondary side three-phase winding current of the transformer 3 calculated in 71C to calculate the exciting current of each phase core winding of the transformer 3. DC component detectors that detect a DC component that causes the iron core of the transformer 3 to reach an eccentric saturation from the calculated excitation current, and 63A to 63C are core windings of each phase of the transformer 3 detected by the DC component detectors 7A to 7C. A subtractor for performing a subtraction for calculating the voltage command correction value for each phase of the self-excited converter 2 from the DC component of the line excitation current,
172A to 172C are multipliers that multiply the outputs of the subtracters 63A to 63C by a constant to calculate the voltage command correction value of each phase of the self-excited converter 2, and 121A to 121C are multipliers 172A to 1C.
Addition for adding the voltage command correction value of each phase of the self-excited converter 2 calculated in 72C and the voltage command value of each phase calculated in the current control means 11 to calculate the final voltage command value of the self-excited converter 2. It is a vessel.

Next, the operation will be described. Current detector 5
When 2A to 52C are provided in the connection between the self-excited converter 2 and the secondary side of the transformer 3, the detectable current is the phase current of each phase. Here, the secondary side phase current of the transformer 3 is Iu2,
Iuv2, Iw2, Iuv2 secondary winding current of the transformer 3
2, (Ivw2, Iwu2), (Equation 3) to (Equation 5) are established. Iwu2 + Iu2 = Iuv2 (Equation 3) Iuv2 + Iv2 = Ivw2 (Equation 4) Ivw2 + Iw2 = Iwu2 (Equation 5) Therefore, from (Equation 3) to (Equation 5), (Equation 6) to (Equation 8) ) Is required. Iuv2 = (Iu2-Iv2) / 3 + (Iuv2 + Iv
w2 + Iwu2) / 3 ...
.. (Equation 6) Ivw2 = (Iv2-Iw2) / 3 + (Iuv2 + Iv
w2 + Iwu2) / 3 ...
.. (Equation 7) Iwu2 = (Iw2-Iu2) / 3 + (Iuv2 + Iv
w2 + Iwu2) / 3 ...
.. (Equation 8) where (Iuv2 + Ivw2 + Iwu2) is a term that appears only when the impedance between the phase windings is unbalanced,
Since it is usually small enough to be ignored, the phase currents Iu2, Iv2, Iw2 are set to zero and the winding currents Iuv2, Ivw are set.
2, Iwu2 can be obtained.

Therefore, in FIG. 6, the secondary side phase currents Iu2, Iv2 and Iw2 of the transformer 3 are detected by the current detectors 52A to 52A-5.
2C, subtraction is performed by the subtracters 61A to 61C,
Since the calculations of (Equation 6) to (Equation 8) can be performed by performing multiplication of 1/3 times in the multipliers 171A to 171C, the secondary winding currents Iuv2, Ivw2 of the transformer 3
Iwu2 can be calculated correctly.

The secondary winding currents of the transformer 3 obtained by the multipliers 171A to 171C are respectively detected by the current detectors 51A to 5A.
Primary side winding current detected by 1C and subtractors 62A to 6A
By subtracting at 2C, the exciting current of the iron core of each phase of the transformer 3 can be obtained as the excited state quantity. The DC components are detected by the DC component detectors 7A to 7C from the exciting currents of the iron cores of the respective phases of the transformer 3 thus obtained, so that the self-excited converter 2 is used as in the first embodiment. The voltage command correction value of each phase to be applied to the iron core of each phase of the transformer 3 can be obtained. In the present embodiment, the configuration of the transformer 3 is the primary side star connection and the secondary side delta connection. Therefore, the calculation of the winding current from the phase current is performed only on the secondary side. If the configuration is primary side delta connection, secondary side star connection (Equation 6) ~
Calculation of the winding current from the phase current corresponding to (Equation 8) is performed on the primary side, and the transformer configuration has a primary side delta connection,
In the case of the secondary side delta connection, the same effect can be expected if the calculation for obtaining the winding current from the phase currents corresponding to (Equation 6) to (Equation 8) is performed on both the primary side and the secondary side.

Since the outputs of the DC component detectors 7A to 7C are voltage command correction values to be applied to the windings of the secondary side cores of the transformer 3, the final voltage command value given to the pulse width modulation control circuit 13 is obtained. Is a phase voltage command value, it is necessary to obtain the secondary side phase voltage applied to the transformer 3 from the winding voltage applied to the secondary side winding of the transformer 3.

The secondary winding voltage of the transformer 3 is set to Vuv2, V
vw2, Vwu2, secondary side phase voltage Vu2, Vv2, V
If w2 is set, (Equation 9) to (Equation 11) are established. Vuv2 = Vu2-Vv2 (Equation 9) Vvw2 = Vv2-Vw2 (Equation 10) Vwu2 = Vw2-Vu2 (Equation 11) Therefore, from (Equation 9) to (Equation 11), (Equation 9) 12) to (Equation 1
4) is required. Vu2 = (Vuv2-Vwu2) / 3 + (Vu2 + Vv
2 + Vw2) / 3 ...
-(Formula 12) Vv2 = (Vvw2-Vuv2) / 3 + (Vu2 + Vv
2 + Vw2) / 3 ...
-(Formula 13) Vw2 = (Vwu2-Vvw2) / 3 + (Vu2 + Vv
2 + Vw2) / 3 ...
(Equation 14) Here, (Vu2 + Vv2 + Vw2) is a term that appears only when the secondary side phase voltage is unbalanced, but if the transformer winding configuration is a delta connection, it is not zero (Vu2 + Vv).
2 + Vw2) component is applied to the phase voltage, as can be seen from (Equation 9) to (Equation 11), the winding voltage Vuv
2, Vvw2, and Vwu2 are not affected, so (Vu
2 + Vv2 + Vw2) is set to zero, and (Expression 12) to (Expression 1)
The calculation of 4) may be performed.

Therefore, the outputs of the DC component detectors 7A-7C are the subtractors 63A-63C and the multipliers 172A-17.
By performing the calculation corresponding to (Equation 12) to (Equation 14) at 2C, the pulse width modulation control circuit 13 is supplied from the voltage command correction value to be applied to the winding of the secondary side each phase core of the transformer 3. Since the phase voltage command correction value to be given can be calculated, it is added by the adders 121A to 121C and given to the pulse width modulation control circuit 13, so that the output voltage of the self-excited converter 2 causes the bias voltage of the transformer 3 to change. The magnetism can be corrected appropriately.

In this embodiment, as means for performing the operations corresponding to (Equation 6) to (Equation 8) and the operations corresponding to (Equation 12) to (Equation 14), multiplication is performed after subtraction. However, the same effect can be expected even if the order of these steps is changed.

Further, as in the first embodiment, the method of obtaining the exciting current by multiplying the coefficient shown in (Equation 1) or (Equation 2) when the turns ratio of the transformer 3 is not 1 has been described.
Magnetomotive force obtained by multiplying the primary winding turns between the current detectors 51A to 51C and the subtractors 62A to 62C and the secondary winding turns between the current detectors 52A to 52C and the subtractors 62A to 62C. Even if is calculated as the excitation state quantity, the same effect can be expected because the quantity is proportional to the excitation current.

Further, as in the first embodiment, the excitation state quantity of the transformer 3 is determined by the current detectors 51A to 51C and 52A to 5A.
Although the difference between the primary side current and the secondary side current of the transformer 3 detected by 2C is obtained by the subtracters 62A to 62C to obtain the exciting current, the current detectors 51A to 51A are obtained.
A voltage detector is used instead of C, 52A to 52C, and even if the excited state quantity is obtained based on the integrated value of the output, or the magnetic flux quantity of the iron core of the transformer 3 is detected, for example, a hall element or a search coil. A magnetic detector is installed to directly connect the transformer 3
The same effect can be obtained even if the excited state quantity of is obtained.

In the case where the excitation state quantity is obtained from the voltage detection result, and the winding of the transformer is delta connected, the winding voltage can be obtained in the following manner.
That is, a phase voltage detector for detecting the phase voltage on the delta connected side is provided, and a subtracter and a multiplier are used from the output of this phase voltage detector in the same manner as described in FIG. The three-phase winding voltage of the windings connected in the delta connection is calculated. Further, as another method, a winding voltage detector for detecting the voltage of each winding on the delta connected side of the transformer may be provided.

Further, when the winding of the transformer is star-connected, a line-voltage detector for detecting the line-voltage on the star-connected side is provided, and from the output of this line-voltage detector, A three-phase winding voltage of the star-connected winding may be calculated using a subtractor and a multiplier.

As described above, in the power converter of the third embodiment shown in FIG. 6, the subtracters 61A to 61C and the multipliers 171A to 171C convert the phase current of the three-phase transformer having the delta winding. Since the winding current can be obtained, the exciting current of each phase core of the three-phase transformer 3 can be accurately obtained, the excited state of the three-phase transformer 3 can be accurately calculated, and the subtractor Since the 63A to 63C and the multipliers 172A to 172C can calculate the phase voltage command correction value to be given to the pulse width modulation control circuit 13 from the voltage command correction value to be applied to the winding of the three-phase transformer 3, An appropriate correction output can be obtained by the output voltage of the self-excited converter 2, the effect of reliably suppressing the DC bias magnetism of the transformer can be obtained, and high continuity of operation can be avoided by avoiding protection stop due to overcurrent. Trustworthy It is possible to provide a conversion device.

Fourth Embodiment FIG. 7: is a block diagram which shows the structure of the power converter device of Embodiment 4 of this invention. In FIG. 7, 18 is a neutral point ground for grounding the neutral point of the primary side star connection of the transformer 3, and 122 is an addition for adding the primary side currents of the transformer 3 detected by the current detectors 51A to 51C. , 173 is a multiplier for multiplying the output of the adder 122 by a constant, and 64A to 64C are multipliers 173.
Is subtracted from the primary side current of the transformer 3 detected by the current detectors 51A to 51C to remove the zero-phase component.

Next, the operation will be described. As shown in FIG. 7, when the neutral point of the primary side star connection of the transformer 3 is grounded, if a ground fault occurs in the AC power system 1, zero-phase current will flow via the neutral point grounding 18. When the zero-phase current contains a DC component, the iron core of the transformer 3 is demagnetized according to the DC component of the zero-phase current. In the power converter of the third embodiment shown in FIG. 6, the zero-phase current remains in the outputs of the subtracters 62A to 62C as it is, but the DC component of the zero-phase component is detected by the DC component detectors 7A to 7C.
When the voltage command correction value is extracted by C and Vuv2 + Vvw2 + Vwu2 = 0 (Equation 15) from (Equation 9) to (Equation 11), the output voltage of the self-excited converter 2 causes a transformer. Three
No secondary phase winding zero phase component voltage can be applied.
For this reason, the output voltage of the self-exciting converter 2 cannot suppress the magnetic bias due to the zero-phase current, and therefore the DC component detectors 7A to 7C must include the DC component until they naturally decay. , But DC component detectors 7A to 7C
Etc. include an integral element, this DC component may saturate a saturation element such as an integral element included in the DC component detectors 7A to 7C.

The power converter of the present embodiment shown in FIG. 7 removes the DC component of the zero-phase component that causes the integration elements included in the DC component detectors 7A to 7C and the like to reach saturation. In FIG. 7, when the neutral point of the primary side star connection is grounded to the primary side current of the transformer 3 detected by the current detectors 51A to 51C, a ground fault accident or the like occurs in the AC power system 1. Then, a zero-phase current may flow through the neutral grounding 18. In this case, the current detectors 51A to 51C
The zero-phase component included in the primary-side current of the transformer 3 detected in 3 is added with the three-phase component in the adder 122, and the multiplier 173 is added.
Can be obtained by multiplying by
The zero phase component can be removed by subtracting from the primary side current of the transformer 3 at 4A to 64C.

The transformer 3 from which the zero-phase component is removed in this way
The primary side current is subtracted from the secondary side current in the subtracters 62A to 62C to obtain the exciting current, and the DC component detectors 7A to 7C, the subtracters 63A to 63C, and the multiplier 172 are obtained.
A-172C is used to obtain the voltage command correction value and adder 121
A-121C acts as a voltage command correction value by being added to the voltage command value output from the current control circuit 11, and even if the primary side current of the transformer 3 includes a zero-phase component, the DC component detector It is possible to avoid saturation of the saturation elements such as integral elements included in 7A to 7C.

In this embodiment, the case where the transformer 3 is composed of the primary side star connection and the secondary side delta connection has been described. Therefore, the calculation for removing the zero-phase component is performed only on the primary side. When the configuration is primary side delta connection or secondary side star connection, the operation to remove the zero-phase component is performed on the secondary side, and when the transformer configuration is primary side star connection or secondary side star connection, zero phase The same effect can be expected if the operation for removing the component is performed on both the primary side and the secondary side.

Further, in the present embodiment, the case where the neutral point of the star connection of the transformer 3 is directly grounded has been described, but even if it is not directly grounded, it is indirectly grounded via a resistor or the like. The same effect can be expected when a zero-phase current path is formed, such as in the case where a neutral point such as a three-phase four-wire system is connected to another neutral point directly or via a resistor. .

Further, as a means for performing the operation for extracting the zero-phase component, the subtraction is followed by the multiplication, but the same effect can be expected even if the order of these is exchanged.

Further, as in the first embodiment, the method of obtaining the exciting current by multiplying the coefficient shown in (Equation 1) or (Equation 2) when the turns ratio of the transformer 3 is not 1 has been described.
A value obtained by multiplying the primary winding turns between the current detectors 51A to 51C and the subtractors 62A to 62C and the secondary winding turns between the current detectors 52A to 52C and the subtractors 62A to 62C. Even if the magnetic force is obtained as the excited state quantity, the same effect can be expected because the quantity is proportional to the exciting current.

Further, as in the first embodiment, the excitation state quantity of the transformer 3 is set to the current detectors 51A to 51C and 52A to 5A.
Although the difference between the primary side current and the secondary side current of the transformer 3 detected by 2C is obtained by the subtracters 62A to 62C to obtain the exciting current, the current detectors 51A to 51A are obtained.
A voltage detector is used instead of C, 52A to 52C, and even if the excited state quantity is obtained based on the integrated value of the output, or the magnetic flux quantity of the iron core of the transformer 3 is detected, for example, a hall element or a search coil. A magnetic detector is installed to directly connect the transformer 3
The same effect can be obtained even if the excited state quantity of is obtained.

As described above, in the power converter of the fourth embodiment shown in FIG. 7, the primary side current of the transformer 3 detected by the current detectors 51A to 51C is added by the adder 122, Multiplier 173 multiplies the constant and subtractors 64A to 64A
By subtracting at 4C, the zero-phase current component flowing from the neutral point of the transformer 3 to the neutral point ground 18 can be removed, and the DC component detectors 7A to 7C and the like have saturation elements such as integral elements. Even if it is included, its saturation can be avoided, so that an appropriate correction output can be obtained by the output voltage of the self-exciting converter 2, and the effect of surely suppressing the DC bias magnetization of the transformer can be obtained. It is possible to provide a highly reliable power converter with high continuity of operation while avoiding protection stop due to overcurrent.

Embodiment 5. FIG. 8: is a block diagram which shows the structure of the power converter device of Embodiment 5 of this invention. The difference from the power conversion device of the third embodiment shown in FIG. 6 is that the current detectors 52A to 52C are not provided in the connection between the transformer 3 and the self-excited converter 2, but
This is a point provided on the secondary side delta winding of the transformer 3 itself.

Next, the operation will be described. In FIG. 8, the winding current of each phase of the secondary winding of the transformer 3 is the current detector 5
Directly detected at 2A-52C. In the power converter of the third embodiment shown in FIG. 6, current detectors 52A to 52C are provided.
Subtractor 61A from the secondary side phase current of transformer 3 detected at
~ 61C, using multipliers 171A-171C (Equation 6)
The secondary winding current of the transformer 3 is obtained by performing the calculation shown in (Equation 8), but (Iuv2 + Ivw2 + I
Since the term wu2) cannot be detected, the secondary side winding current of the transformer 3 is obtained assuming that this is zero.

Generally, (Iuv2 + Ivw2 + Iwu2)
Is a term that appears only when the impedance between the phase windings is unbalanced, and is usually negligibly small. For example, when the transformer core of only a certain phase winding is near the saturation region, The impedance may be unbalanced due to the non-linear relationship between the excitation current and the magnetic flux of the transformer winding shown in (3), and in that case (Iuv2 + Ivw2 + Iwu2) does not become zero, so the DC component of the excitation current of the transformer 3 May be erroneously detected.

In the power converter of the fifth embodiment shown in FIG. 8, since the current detectors 52A to 52C are provided on the secondary winding itself of the transformer 3, the secondary winding of the transformer 3 is provided. Since the current can always be detected accurately and the detected value is the immediate winding current, the subtractors 61A to 61C and the multipliers 171A to 171C in the power conversion device according to the third embodiment shown in FIG. 6 are used.
Current detector 52A to
The exciting current of the transformer 3 can be obtained by directly subtracting the output of 52C by the subtractors 62A to 62C, and the number of parts or the calculation time can be reduced.

In this way, the secondary winding current of the transformer 3 detected by the current detectors 52A to 52C is the current detector 5
The exciting current is calculated by subtracting the primary side current of the transformer 3 detected by 1A to 51C and the subtractors 62A to 62C, and the DC component is detected by the DC component detectors 7A to 7C, and subtracted. 63A to 63C, multiplier 172A to
At 172C, the phase voltage command correction value to be given to the pulse width modulation control circuit 13 is calculated, and the adders 121A to 121A-12
It is added at 1C and acts as a phase voltage command correction value.

In the present embodiment, the configuration of the transformer 3 is the primary side star connection and the secondary side delta connection. Therefore, the installation location of the current detector is changed only on the secondary side. If the transformer configuration is the primary side delta connection or the secondary side star connection, the installation location of the current detector is changed for the primary side, and if the transformer configuration is the primary side delta connection or the secondary side delta connection, the current The same effect can be expected if the detector installation location is changed on both the primary side and the secondary side.

Similarly to the first embodiment, the method of obtaining the exciting current by multiplying the coefficient shown in (Equation 1) or (Equation 2) when the turns ratio of the transformer 3 is not 1 has been described.
A value obtained by multiplying the primary winding turns between the current detectors 51A to 51C and the subtractors 62A to 62C and the secondary winding turns between the current detectors 52A to 52C and the subtractors 62A to 62C. Even if the magnetic force is obtained as the excited state quantity, the same effect can be expected because the quantity is proportional to the exciting current.

Further, as in the first embodiment, the excitation state quantity of the transformer 3 is changed to the current detectors 51A to 51C and 52A to 52.
The difference between the primary side current and the secondary side current of the transformer 3 detected at C is obtained by subtracting the exciting currents by the subtracters 62A to 62C, but the current detectors 51A to 51A are used.
A voltage detector is used instead of C, 52A to 52C, and even if the excited state quantity is obtained based on the integrated value of the output, or the magnetic flux quantity of the iron core of the transformer 3 is detected, for example, a hall element or a search coil. A magnetic detector is installed to directly connect the transformer 3
The same effect can be obtained even if the excited state quantity of is obtained.

When the primary side neutral point of the transformer 3 is grounded, the zero-phase current removing means used in the fourth embodiment may also be provided in the present embodiment in the same manner as in the fourth embodiment. The effect is obtained.

As described above, in the power converter of the fifth embodiment shown in FIG. 8, the current detectors 52A to 52C are provided in the secondary winding of the transformer 3, so that the transformer 3 Since it is possible to accurately detect the secondary winding current, it is possible to accurately obtain the exciting current of each iron core of the three-phase transformer,
Since the excited state quantity of the three-phase transformer can be accurately calculated, an appropriate correction output can be obtained by the output voltage of the self-excited converter 2, and the effect of surely suppressing the DC bias magnetization of the transformer. Therefore, it is possible to provide a highly reliable power conversion device having high continuity of operation while avoiding protection stop due to overcurrent.

In the first and second embodiments, a single-phase configuration has been described for simplification of description, but a multi-phase configuration of two or more phases is also possible, and a three-phase configuration may be used. Connection is star / star connection or star / delta connection Delta /
The same effect can be obtained by using the same method even in the delta connection.

Further, in the first to fifth embodiments,
Although the description has been given with the configuration of only one stage of the transformer, even in the multi-stage configuration in which the primary side or the secondary side is connected in series, multiple connections are made with the outer iron type transformer or the inner iron type transformer via the common magnetic path. Even in this case, the same effect can be obtained.

Further, in the first to fifth embodiments,
A self-excited converter using a semiconductor element capable of self-extinguishing such as GTO, GCT, IGBT, and transistor has been described as a converter for generating a voltage according to the output of the pulse width modulation control circuit 13. Any converter such as a thyristor converter or a cycloconverter may be used as long as it is a converter that generates a voltage.

[0090]

As described above, the power conversion device according to the present invention is a power conversion device connected to an AC line via a transformer, and the excitation state quantity for detecting the excitation state quantity of the transformer. Detecting means, direct current component detecting means for detecting a direct current component of the output from the excitation state quantity detecting means, and a value obtained by adding the output to the voltage command value so that the output from the direct current component detecting means becomes a predetermined target value. A control means for controlling the output voltage of the power converter based on the above-mentioned, wherein it is inserted between the excitation state quantity detection means and the DC component detection means or between the DC component detection means and the control means. Output is performed only when the input is less than or equal to the first set value or greater than or equal to the second set value greater than the first set value, and the input exceeds the first set value and the second set value is exceeded. Output when less than the value Since the dead zone means that does not perform is provided, in particular, the dead zone means removes the offset, noise, and alias noise caused by the switching ripple of the power conversion device included in the excitation state quantity, and adds an incorrect DC component to the voltage command value. This eliminates the risk of causing the transformer to become unnecessarily demagnetized, reliably suppresses DC demagnetization of the transformer, avoids protection stop due to overcurrent, and provides a highly reliable power converter with high operational continuity. There is an effect that can be.

Further, the power conversion device according to the present invention is a power conversion device connected to an AC line via a transformer, the excitation state quantity detecting means for detecting the excitation state quantity of the transformer, and the excitation state quantity detecting means. DC component detecting means for detecting a DC component of the output from the state quantity detecting means, and the power conversion based on a value obtained by adding the output to the voltage command value so that the output from the DC component detecting means becomes a predetermined target value. In a device provided with a control means for controlling the output voltage of the device, it is inserted between the excitation state quantity detection means and the direct current component detection means or between the direct current component detection means and the control means,
When the input is less than or equal to the first set value or greater than or equal to the second set value greater than the first set value, the limiter means for performing the output limiting the input is provided. Even if the excited state quantity suddenly changes in the vicinity of the saturation area of the iron core, there is no risk of adding an excessive erroneous DC component to the voltage command value and causing the transformer to become an undesired biased state. There is an effect that it is possible to provide a highly reliable power conversion device that is reliably suppressed and avoids protection stop due to overcurrent and that has high operation continuity.

Further, the excitation state quantity detecting means of the power converter according to the present invention detects the primary side current of the transformer.
Current detector, second for detecting the secondary side current of the transformer
Of the current detector and the exciting current calculating means for calculating the exciting current of the transformer based on the output difference between the two current detectors, and the exciting current is output as the excited state quantity of the transformer. It is possible to directly obtain the exciting current, which is the excited state quantity of, from the current detector.

Further, the excitation state quantity detecting means of the power converter according to the present invention is the first for detecting the primary side voltage of the transformer.
Voltage detector, second for detecting the secondary voltage of the transformer
A voltage detector, and a magnetic flux amount calculating means for calculating the magnetic flux amount of the transformer based on the outputs of both the voltage detectors,
Since the magnetic flux amount is output as the excited state amount of the transformer, the magnetic flux amount, which is the excited state amount of the transformer, can be obtained from the integral calculation output of the output of the voltage detector.

Further, the excitation state quantity detecting means of the power converter according to the present invention comprises magnetic flux quantity detecting means for detecting the amount of magnetic flux flowing in the iron core of the transformer, and the magnetic flux quantity is used as the excitation state quantity of the transformer. Since it is output, the amount of magnetic flux, which is the amount of excitation of the transformer, can be directly obtained from the magnetic flux amount detecting means.

The power converter according to the present invention is a power converter connected to an AC line via a three-phase transformer, and is in an excited state for detecting the three-phase excited state quantity of the transformer. Quantity detecting means, DC component detecting means for detecting the DC component of the three-phase output from the excitation state quantity detecting means, and this DC
Make sure that the three-phase output from the component detection means reaches the specified target value.
Addition correction to the three-phase voltage command value with the correction value according to the output
Then, the power conversion is performed based on the corrected three-phase voltage command value.
Control means for controlling the output voltage of the device, and the direct current component
Minute detection means and the control means, the DC
Converts the three-phase output from the component detector to a three-phase voltage output
And a three-phase output from the phase voltage calculating means.
Add the phase voltage output to the above three-phase voltage command value as the above correction value.
Since it was calculated, the three-phase
Correct the addition to the pressure command value based on the phase voltage reference
It is possible to suppress DC bias magnetism in the case of a three-phase transformer, and
High reliability with high continuity of operation avoiding protection stop due to electric current
There is an effect that a power conversion device can be provided.

The excitation state quantity detecting means of the power converter according to the present invention is the first current detecting means for detecting the primary side three-phase winding current of the transformer, and the secondary side three-phase winding of the transformer. A second current detecting means for detecting a line current and an exciting current calculating means for calculating a three-phase exciting current of the transformer based on an output difference between the both current detecting means are provided, and the three-phase exciting current is converted into the transformer. Is output as the three-phase excitation state quantity of, the three-phase excitation current, which is the excitation state quantity of the three-phase transformer, can be directly obtained from the current detector.

The excitation state quantity detecting means of the power converter according to the present invention is the first voltage detecting means for detecting the primary side three-phase voltage of the transformer, and the secondary side three-phase voltage of the transformer. Second voltage detecting means, and magnetic flux amount calculating means for calculating the three-phase magnetic flux amount of the transformer based on the outputs of both the voltage detecting means, and the three-phase magnetic flux amount for the three-phase excitation state of the transformer. Since it is output as a quantity, the three-phase magnetic flux quantity, which is the excited state quantity of the three-phase transformer, can be obtained from the integral calculation output of the output of the voltage detector.

Further, the excitation state quantity detecting means of the power converter according to the present invention comprises magnetic flux quantity detecting means for detecting the three-phase magnetic flux quantity flowing in the iron core of the transformer, and the three-phase magnetic flux quantity is detected by the transformer. Since the three-phase excitation state quantity is output, the three-phase magnetic flux quantity, which is the excitation state quantity of the three-phase transformer, can be directly obtained from the magnetic flux quantity detecting means.

Further, in the power converter according to the present invention, when the winding on the primary side or the secondary side of the transformer is star-connected to form the zero-phase current path, the excitation state quantity detecting means is: Since the zero-phase component is detected from the three-phase excitation state quantity and the zero-phase component is subtracted from the above-mentioned three-phase excitation state quantity, the saturated element such as an integral element is output to the DC component detector. Even if the power supply contains a high-reliability power converter, its saturation can be avoided, DC bias magnetism of the three-phase transformer can be reliably suppressed, and protection stop due to overcurrent can be avoided to ensure high operational continuity. There is an effect that can be provided.

Further, in the power converter according to the present invention, when the primary winding or secondary winding of the transformer is delta connected, the current detecting means on the delta connected side is Since the phase current detector for detecting the phase current on the delta connected side and the winding current calculation means for calculating the three-phase winding current of the delta connected winding from the output of this phase current detector are provided. It is possible to detect the winding current of each phase of the three-phase winding in the delta connection of the transformer, and obtain an accurate three-phase exciting current as the excited state quantity.

Further, in the power converter according to the present invention, when the primary winding or the secondary winding of the transformer is delta connected, the current detecting means on the delta connected side is Since a winding current detector that is inserted in each winding on the Delta-connected side and detects the winding current of the above-mentioned three-phase winding is provided, each phase winding current of the three-phase winding Delta-connected in the transformer Can be detected, and an accurate three-phase excitation current as an excitation state quantity can be obtained.

Further, in the power converter according to the present invention, when the winding on the primary side or the secondary side of the transformer is star-connected to form the zero-phase current path, the star-connected side of the transformer is connected. The current detection means includes a winding current detector that detects the winding current on the star-connected side, a zero-phase component detector that detects a zero-phase component of the output from the winding current detector, and the winding. Since the output of the current detector is subtracted from the zero-phase component to output a winding current of three phases, the output of the winding current detector provided on the star-connected side itself provides three-phase It becomes possible to remove the zero-phase component from the exciting current, and even if the DC component detector contains a saturation element such as an integral element, the saturation can be avoided and the DC bias of the three-phase transformer can be avoided. Surely suppress magnetism and avoid protection stop due to overcurrent There is an effect that it is possible to provide a rolling continuity highly reliable power conversion apparatus.

Further, in the power converter according to the present invention, when the primary winding or secondary winding of the transformer is delta connected, the voltage detecting means on the delta connected side is Since the phase voltage detector for detecting the phase voltage on the delta connected side and the winding voltage calculation means for calculating the three-phase winding voltage of the delta connected winding from the output of this phase voltage detector are provided. It is possible to detect the winding voltage of each phase of the three-phase winding in the delta connection of the transformer, and obtain the three-phase magnetic flux amount as the excited state amount based on the integrated calculation output.

Further, in the power converter according to the present invention, when the primary winding or secondary winding of the transformer is delta-connected, the voltage detecting means on the delta-connected side is the above-mentioned one. Since a winding voltage detector that detects the voltage of each winding on the delta connected side is provided, it is possible to detect each phase winding voltage of the three-phase winding on the delta connection of the transformer, and based on the integral calculation output It is possible to obtain the three-phase magnetic flux amount as the excited state amount.

Further, in the power converter according to the present invention, when the primary winding or the secondary winding of the transformer is star-connected, the voltage detecting means on the star-connected side is the above-mentioned. A line voltage detector that detects the line voltage on the star-connected side, and a winding voltage calculation means that calculates the three-phase winding voltage of the star-connected winding from the output of this line voltage detector. Since it is provided, the voltage of each phase winding of the three-phase winding star-connected to the transformer can be detected, and the three-phase magnetic flux amount as the excited state amount can be obtained based on the integral calculation output.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a power conversion device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of the dead zone means 15 of FIG.

FIG. 3 is a diagram for explaining the operation of the dead zone means 15 of FIG.

FIG. 4 is a configuration diagram showing a power conversion device according to a second embodiment of the present invention.

5 is a characteristic diagram of the limiter means 16 of FIG.

FIG. 6 is a configuration diagram showing a power conversion device according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram showing a power conversion device according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram showing a power conversion device according to a fifth embodiment of the present invention.

FIG. 9 is a configuration diagram showing a conventional power conversion device.

FIG. 10 is a diagram showing a relationship between an exciting current and a magnetic flux of a transformer core.

[Explanation of symbols]

1 AC power system, 2 self-excited converter, 3 transformer, 4
DC voltage source, 5A, 5B, 51A to 51C, 52A
52C current detector, 6, 61A to 61C, 62A to 6
2C, 63A to 63C, 64A to 64C Subtractor, 7
DC component detector, 8 voltage detector, 9 system voltage reference,
10 system voltage control means, 11 current control means, 12,
121A to 121C adder, 13 pulse width modulation control circuit, 14 gate pulse amplification circuit, 15 dead zone means, 16 limiter means, 171A to 171C, 172
A to 172C multiplier, 18 neutral ground, T1 1st
Setting value of, T2 second setting value.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Funabashi 2-3-3 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Takeshi Kakuo 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Incorporated (56) Reference JP 7-25834 (JP, A) JP 59-53084 (JP, A) JP 61-92128 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 7/155 H02H 7/045

Claims (16)

(57) [Claims] 1. A power conversion device connected to an AC line via a transformer, the excitation state quantity detecting means for detecting an excitation state quantity of the transformer, and a DC output from the excitation state quantity detecting means. DC component detecting means for detecting a component, and control means for controlling the output voltage of the power converter based on a value obtained by adding the output to the voltage command value so that the output from the DC component detecting means becomes a predetermined target value. When the input is less than or equal to a first set value or is inserted between the excitation state quantity detection means and the DC component detection means or between the DC component detection means and the control means, A dead zone means is provided which outputs only when the second set value is larger than the first set value and is more than the second set value, and does not output when the input exceeds the first set value and is less than the second set value. Characterized by Power conversion equipment. 2. A power conversion device connected to an AC line via a transformer, the excitation state quantity detecting means for detecting an excitation state quantity of the transformer, and a direct current output from the excitation state quantity detecting means. DC component detecting means for detecting a component, and control means for controlling the output voltage of the power converter based on a value obtained by adding the output to the voltage command value so that the output from the DC component detecting means becomes a predetermined target value. When the input is less than or equal to a first set value or is inserted between the excitation state quantity detection means and the DC component detection means or between the DC component detection means and the control means, A power conversion device comprising: a limiter means for performing an output with the input limited when the value is equal to or larger than a second set value that is larger than the first set value. 3. The excitation state quantity detecting means comprises a first current detector for detecting a primary side current of the transformer, a second current detector for detecting a secondary side current of the transformer, and the both currents. 3. The electric power according to claim 1, further comprising: an exciting current calculating means for calculating an exciting current of the transformer based on an output difference of the detector, and the exciting current is output as an excited state quantity of the transformer. Converter. 4. The excitation state quantity detecting means comprises a first voltage detector for detecting a primary side voltage of the transformer, a second voltage detector for detecting a secondary side voltage of the transformer, and the both voltages. The power conversion according to claim 1 or 2, further comprising: a magnetic flux amount calculating means for calculating a magnetic flux amount of the transformer based on an output of a detector, and outputting the magnetic flux amount as an excitation state amount of the transformer. apparatus. 5. The excitation state quantity detection means comprises a magnetic flux quantity detection means for detecting the amount of magnetic flux flowing in the iron core of the transformer, and outputs the magnetic flux quantity as the excitation state quantity of the transformer. The power converter according to item 1 or 2. 6. Connected to an AC line via a three-phase transformer
Of the above-mentioned transformer, the excitation state quantity detection for detecting the three-phase excitation state quantity of the transformer.
Output means, DC of three-phase output from this excitation state quantity detection means
DC component detection means for detecting components, this DC component detection hand
The three-phase voltage indicator so that the three-phase output from the stage reaches the specified target value.
Correction value is added to the command value with a correction value according to the output, and the correction is performed.
Output of the power converter based on the three-phase voltage command value
Control means for controlling voltage, and DC component detecting means
Is inserted between the control means and
Phase voltage calculation to convert the three-phase output from the stage to the three-phase voltage output
And a three-phase phase voltage output from the phase voltage calculation means as the correction value.
And adding to the above three-phase voltage command value.
Force converter. 7. An excitation state quantity detecting means is a primary side of a transformer.
First current detecting means for detecting three-phase winding current, the transformer
Second current detector for detecting the secondary side three-phase winding current of the transformer
Stage, and the above-mentioned change based on the output difference of both current detection means.
Equipped with exciting current calculation means to calculate the three-phase exciting current of the pressure device
The three-phase excitation current is the three-phase excitation state quantity of the transformer.
7. The power conversion according to claim 6, wherein
apparatus. 8. An excitation state quantity detecting means is a primary side of a transformer.
The first voltage-detection means for detecting the three-phase voltage, the transformer
Second voltage detecting means for detecting a secondary-side three-phase voltage, and
Based on the outputs of both the voltage detection means, the three-phase magnet of the transformer
The three-phase magnetic flux amount is provided with a magnetic flux amount calculating means for calculating the flux amount.
Is output as the three-phase excitation state quantity of the above transformer.
The power conversion device according to claim 6, which is a characteristic. 9. An excitation state quantity detecting means is provided in an iron core of a transformer.
Equipped with a magnetic flux amount detecting means for detecting the flowing three-phase magnetic flux amount,
Output the three-phase magnetic flux amount as the three-phase excitation state amount of the above transformer
The power conversion device according to claim 6, wherein 10. The winding on the primary or secondary side of the transformer
In case of star connection and its zero-phase current path is formed,
The excitation state quantity detecting means detects the zero phase from the excitation state quantity of three phases.
Component is detected and the zero-phase component is calculated from the excitation state quantities of the three phases.
Claim that is characterized by outputting the subtracted one
Item 10. The power conversion device according to any one of items 6 to 9. 11. The winding on the primary or secondary side of the transformer
If it is a delta connection, the delta connection
The current detection means on the side of the
Phase current detector that detects the current, and this phase current detector
Calculate the three-phase winding current of the above delta connected winding from the output
A winding current calculating means for outputting is provided.
Item 7. The power conversion device according to item 7. 12. The transformer primary or secondary winding is
If it is a delta connection, the delta connection
The current detection means on the open side is for each winding on the side connected to the delta connection.
Winding current that is inserted in the wire and detects the winding current of the above three-phase winding.
Power according to claim 7, characterized in that it comprises a current detector.
Converter. 13. The winding on the primary or secondary side of the transformer
In case of star connection and its zero-phase current path is formed,
The current detection means on the side of the star connection is the star
A winding current detector that detects the winding current on the connected side.
Phase detecting the zero phase component of the output from the winding current detector
From the component detector and the output of the winding current detector,
Equipped with a subtractor that subtracts zero-phase component and outputs three-phase winding current
The power conversion device according to claim 7, wherein the power conversion device is obtained. 14. The winding on the primary or secondary side of the transformer
If it is a delta connection, the delta connection
The voltage detecting means on the side of the
Phase voltage detector that detects pressure, and this phase voltage detector
From the output, calculate the three-phase winding voltage of the above delta-connected winding
A winding voltage calculating means for outputting is provided.
Item 8. The power conversion device according to item 8. 15. The winding on the primary or secondary side of the transformer
If it is a delta connection, the delta connection
The voltage detecting means on the closed side is the winding on the side connected to the delta connection.
Features a winding voltage detector that detects the voltage of the wire
The power conversion device according to claim 8. 16. The winding on the primary or secondary side of the transformer
If it is star-connected, it is
The voltage detection means on the closed side is between the lines on the side connected to the star.
A line voltage detector that detects voltage, and this line voltage detector
From the output of the generator, the three-phase winding
A winding voltage calculating means for calculating the pressure is provided.
The power conversion device according to claim 8.