JP2008228491A - Control method for inverter device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress bias magnetization of a transformer caused by residual magnetic flux when gate deblocking a self-excited converter for supplying AC power to a load via the transformer, after gate blocking the self-excited converter. <P>SOLUTION: In the inverter device for supplying AC output to a load via a transformer, a first mode for simultaneously providing a gate pulse to the upper side arm of a first half bridge circuit and to the lower side arm of a second half bridge circuit which constitute the self-excited converter 1, and a second mode for simultaneously providing a gate pulse to the lower side arm of the first half bridge circuit and to the upper arm of the second half bridge circuit which constitute the self-excited converter 1, are operated alternately and repeatedly in normal operation. Furthermore, when it is detected that the AC output current, detected by an AC current detector 5 reaches an overcurrent protection level and one arm is, gate-deblocked after being gate blocked, the pulse width of the initial gate pulse to be provided to the other arm is shortened by only the period matching the residual magnetic flux of the transformer 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, in a single-phase self-excited converter in which a DC input side is connected to a DC voltage source and an AC output side is connected to a load via a transformer, the bias magnetism of the transformer is reduced at the time of gate block. The present invention relates to a control method for an inverter device.

  Conventionally, as an inverter device that converts a DC voltage to an AC voltage by a self-excited converter and supplies the output to the AC power system, the AC output is stopped by gate-blocking when an abnormality occurs in the AC power system. When the abnormality is resolved, the gate is deblocked and the AC output synchronized with the voltage of the AC power system is resumed. , See Patent Document 1).

This inverter device detects the phase of the voltage of the AC power system with a voltage phase detection circuit, and executes the gate deblocking of the self-excited converter at the timing of the voltage of the AC power system with zero voltage. An increase in the amount of bias is suppressed.
JP2002-032132

  However, when a DC voltage is converted into an AC voltage by a self-excited converter as in the above inverter device, and the output is supplied to the AC power system via a transformer, the bias of the transformer during gate deblocking Although an increase in the amount can be suppressed, it cannot be applied to an inverter device for converting a DC voltage into an AC voltage by a self-excited converter and supplying the output to a load via a transformer.

  The present invention has been made to solve the above problems, and in an inverter device for use in which AC output is supplied to a load via a transformer, the bias of the transformer due to residual magnetic flux during gate deblocking. It is an object of the present invention to provide a control method for an inverter device that can reduce the noise.

  In order to achieve the above object, the present invention controls an inverter device by the following means.

The present invention is configured by combining two self-extinguishing switching elements and two half-bridge circuits in which an arm formed by connecting a diode in reverse parallel to the switching element is connected in series, and the DC input side is connected to a DC voltage source. A single-phase self-excited converter whose AC output side is connected to a load via a transformer;
An inverter device comprising control means for operating the self-excited converter in a predetermined gate pulse pattern and outputting a voltage corresponding to a command value to an alternating current side, wherein the transformer includes the transformer from the self-excited converter AC current detecting means for detecting a current flowing through the load via the control means is provided, and the control means is configured such that when the control means is in a normal operation state, the upper arm of the first half bridge circuit and the second half bridge circuit A first mode in which a gate pulse is simultaneously applied to the lower arm of the second half, and a second mode in which a gate pulse is simultaneously applied to the lower arm of the first half bridge circuit and the upper arm of the second half bridge circuit. Overcurrent protection in which the AC output current of the self-excited converter detected by the AC current detecting means is set in advance. And gate blocking one arm to reach the bell, then for a period commensurate with the residual magnetic flux of the transformer when gate deblocking, to shorten the pulse width of the first gate pulse applied to the other arm.

  According to the present invention, in an inverter device for supplying AC output to a load via a transformer, the bias of the transformer due to residual magnetic flux is reduced during gate deblocking, and the self-excited converter is caused by excessive inrush current. It is possible to prevent a serious failure trip.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit configuration diagram showing a first embodiment for explaining a control method of an inverter device according to the present invention.

  In FIG. 1, reference numeral 1 is a combination of two self-extinguishing switching elements and two half-bridge circuits in which arms 1a, 1b, 1c, and 1d formed by connecting diodes in anti-parallel to the switching elements are connected in series. In a single-phase voltage type self-excited converter, a DC voltage source 2 is connected between the DC input terminals of the voltage type self-excited converter 1, and a load 4 is connected to the AC output terminal via a transformer 3. .

  Reference numeral 5 denotes a current detector provided on a line connecting the self-excited converter 1 and the transformer 3, and reference numeral 6 denotes a control in which an AC output current detected by the current detector 5 and an operation command 7 are input. In the circuit, the control circuit 6 outputs a gate oscillation command 8 based on the operation command 7.

  Further, 9 is an oscillator that outputs a synchronization signal of a gate pulse, and 10 is a gate that calculates gate block timing and gate deblock timing based on a gate oscillation command 8 input from the control circuit 6 and a synchronization signal input from the oscillator 9. A timing arithmetic unit 11 is a gate pulse amplifier circuit that amplifies the gate block timing signal and the gate deblock timing signal given from the gate timing arithmetic unit 10 and gives them to the self-excited converter 1.

  In the figure, V is a voltage between AC terminals of the self-excited converter 1.

  Next, the operation of the control method of the inverter device configured as described above will be described with reference to FIG.

  2, (a) is a synchronizing signal output from the oscillator 9, (b) is a voltage V between the AC terminals of the self-excited converter 1, (c) is a magnetic flux level of the transformer 3, and (d) is a current. Current detected by the detector 5, (e) to the arm 1a of the self-excited converter 1, (f) to the same arm 1b, (g) to the same arm 1c, (h) to the same arm 1d, respectively. The gate signal to be given is shown.

  The example shown in FIG. 2 is for explaining a series of operations in the case where the inverter device detects an overcurrent, performs gate blocking, and then performs gate deblocking.

  First, the normal operation state before time t21 in FIG. 2 will be described.

  When the operation command 7 is given to the control circuit 6, the control circuit 6 gives the gate oscillation command 8 to the gate timing arithmetic device 10. The gate timing arithmetic unit 10 gives a gate pulse to the self-excited converter 1 through the gate pulse amplifier circuit 11 based on the synchronization signal of the oscillator 9. As a result, the self-excited converter 1 converts the DC voltage of the DC voltage source 2 into an AC voltage and supplies AC power to the load 4 via the transformer 3.

  At this time, in the self-excited converter 1, the combination of the arms 1a and 1d and the arms 1b and 1c is synchronized with the synchronizing signal of the oscillator 9 shown in (a) (e), (f), (g), ( As shown in h), gate pulses are alternately supplied.

  As a result, the AC output voltage of the self-excited converter 1 becomes a rectangular wave as shown in the waveform (b). In this case, when the load 4 is an inductive load, the current detected by the current detector 5 is a sawtooth wave as shown in (d). Further, the magnetic flux level of the transformer 3 changes as shown in the waveform (c) in accordance with the rectangular wave voltage of the above (b).

  Next, the operation when an overcurrent flows at time t21 will be described.

  For example, at the time t21 when the arms 1a and 1d are in the conductive state, when the AC output current detected by the current detector 5 reaches the overcurrent protection level set in the control circuit 6 as shown in (d), The control circuit 6 stops the gate pulse of either the arm 1a or the arm 1d. In this example, the arm 1a is gate-blocked as shown in FIG.

  As a result, the gate period of the self-extinguishing switching element of the arm 1a is shortened by a period T21 shown in (e). Since the output voltage shown in (b) becomes zero by the gate block of the arm 1a, the magnetic flux level of the transformer 3 is held at the time of the gate block of the arm 1a as shown in (c).

  Next, in the next cycle after the gate block, the control circuit 6 first deblocks the other arms 1b and 1c and then gives the first gate pulse. The timing for applying the gate pulse is synchronized with the synchronization signal output from the oscillator 9, but the gate timing arithmetic circuit 10 has a period (the period T21) of the same length as the gate period (period T21) of the arms 1a and 1d shortened by the previous gate block. Only in the period T22) of (f), the timing for applying the first gate pulse is delayed to shorten the gate conduction period.

  Therefore, although the magnetic flux level of the transformer 3 starts to increase due to the gate deblocking, the gate pulse width is shortened, so that the magnetic flux is not excessively demagnetized as shown in (c). If the initial gate pulse width is not shortened during gate deblocking, there is a possibility that a large inrush current will flow due to saturation of the iron core, and there is a possibility that the overcurrent flowing through the self-excited converter 1 will be detected again and gate blocked. is there.

  As described above, in the first embodiment, it is possible to prevent the transformer 3 from being excessively demagnetized by shortening the gate conduction period of the first conducting arm when the gate is deblocked after the gate block. Since the risk of the self-excited converter 1 stopping the gate block again due to an excessive inrush current due to saturation of the transformer core is reduced, an inverter device with high operation continuity can be obtained.

  FIG. 3 is a diagram showing a time chart in the second embodiment of the control method of the inverter device according to the present invention, and the circuit configuration diagram is the same as FIG.

  In the first embodiment, only one of the arms 1a and 1c that has been conducting at time t21 in FIG. 2 is gate-blocked. However, in the second embodiment, both arms are gate-blocked. It is what I did.

  That is, at time t31 when the arms 1a and 1d are in the conductive state as shown in FIG. 3, the overcurrent protection in which the AC output current detected by the current detector 5 is set in the control circuit 6 as shown in (d). When the level is reached, the control circuit 6 simultaneously stops the gate pulses of the arm 1a and the arm 1d.

  As a result, the gate period of the self-extinguishing switching elements of the arm 1a and the arm 1d is shortened by a period T31 shown in FIG. When the gate pulse is stopped, the antiparallel diodes of the arms 1b and 1c are turned on, so that a voltage is applied only during the period T32 during which the antiparallel diode is turned on as shown in (b), and the magnetic flux of the transformer 3 is (c As shown in (), it is held when the voltage becomes zero.

  Next, in the next cycle after the gate block, the control circuit 6 first deblocks the other arms 1b and 1c and then gives the first gate pulse. The timing of applying the gate pulse is synchronized with the synchronizing signal output from the oscillator 9, but the gate timing arithmetic circuit 10 is the reverse of the arms 1a and 1d during the gate period (period T31) of the arms 1a and 1d shortened by the previous gate block. The gate conduction period is shortened by delaying the timing of applying the first gate pulse only during a period (period T33 of (f)) in which a time commensurate with the period during which the parallel diodes are conducting and the voltage is applied (period T32). .

  Accordingly, the magnetic flux level of the transformer 3 starts to increase due to the gate deblocking. However, since the gate pulse width is shortened in consideration of the periods T31 and T32, the magnetic flux is excessively demagnetized as shown in (c). Never do.

  Also in the control method of the inverter device having such a configuration, the same effect as that of the first embodiment can be obtained.

The circuit block diagram which shows 1st Embodiment for demonstrating the control system of the inverter apparatus by this invention. The time chart which shows the waveform of each part in the embodiment. The time chart which shows the waveform of each part in the 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Single-phase voltage type self-excited converter, 1a, 1b, 1c, 1d ... Self-extinguishing type switching element and an arm formed by connecting a diode to this switching element in antiparallel, 2 ... DC voltage source, 3 ... Transformer, 4 ... Load, 5 ... Current detector, 6 ... Control circuit, 7 ... Operation command, 8 ... Gate oscillation command, 9 ... Oscillator, 10 ... Gate timing arithmetic circuit, 11 ... Gate pulse amplification circuit

Claims (3)

Constructed by combining two self-extinguishing type switching elements and two half-bridge circuits in series of arms made by connecting diodes in anti-parallel to the switching elements, and the DC input side is connected to a DC voltage source for AC output A single-phase self-excited converter whose side is connected to the load via a transformer;
An inverter device comprising a control means for operating the self-excited converter with a predetermined gate pulse pattern and outputting a voltage corresponding to a command value to the AC side,
AC current detecting means for detecting a current flowing through a load from the self-excited converter through the transformer is provided,
The control means includes a first mode for simultaneously applying a gate pulse to the upper arm of the first half-bridge circuit and the lower arm of the second half-bridge circuit when in the normal operation state; The second mode in which gate pulses are simultaneously applied to the lower arm of the half bridge circuit and the upper arm of the second half bridge circuit are alternately and repeatedly operated, and the AC current detecting means detects the second mode. When the AC output current of the self-excited converter reaches a preset overcurrent protection level, one arm is gate-blocked, and then the other arm is only for a period commensurate with the residual magnetic flux of the transformer when the gate is deblocked. A control method for an inverter device, characterized by shortening the pulse width of the first gate pulse given to.   The control means shortens the pulse width of the first gate pulse applied to the other arm during the gate deblocking by a period equal to the conduction period of the arm reduced during the gate block. Inverter control method.   The control means is characterized in that the initial pulse width given to the other arm during gate deblocking is shortened only during a period commensurate with the conduction period of the arm reduced during the gate block and the subsequent antiparallel diode conduction period. The control method of the inverter device according to claim 1.

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