JPH0662579A - Voltage-type inverter device - Google Patents

Abstract

(57) [Abstract] [Purpose] The output current of the inverter is detected, the phase of the current detection signal is advanced by a predetermined value, the phase lead is corrected, and the polarity of the obtained correction current detection signal is positive / negative / intermittent. The torque ripple of the electric motor is suppressed by correcting the voltage command with the compensation voltage based on the mode. The object is to provide a means for judging the polarity of the output current as three modes of positive / negative and intermittent which changes the polarity at each switching. When the output current is in the intermittent mode, the compensation voltage of the phase is determined. It can be achieved by setting it to zero. Further, the above object can be achieved by providing means for advancing the phase of the detection signal of the output current by a predetermined value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a voltage source inverter, and more particularly to a pulse width modulation inverter (hereinafter PW).
(Referred to as M inverter) for compensating the waveform distortion of the output voltage.

[0002]

2. Description of the Related Art In a PWM inverter, positive-side and negative-side switching elements forming the inverter are alternately conductively controlled to PWM-control an output voltage. However, since the switching element has a delay in switching due to the turn-off time, a short-circuit prevention period (hereinafter referred to as dead time) is provided so that the positive side and the negative side do not conduct at the same time.
Therefore, there is a problem in that the output voltage of the inverter is distorted due to the dead time.

Conventionally, as a countermeasure against this, Japanese Examined Patent Publication No. 59-8152
As described in Japanese Patent Publication No. JP-A-2003-264, there is known one that is provided with a compensating means for detecting the output current polarity of the inverter for each phase and compensating the waveform distortion of the output voltage of the inverter due to the influence of the dead time based on this polarity signal. Has been.

[0004]

In the above-mentioned prior art, the compensation voltage is determined according to the polarity of the output current. However, when the output current is near zero, the compensation voltage does not match the distortion voltage due to dead time, and the waveform There is a problem in that distortion compensation is not performed correctly, the output voltage waveform does not become a sine wave, and torque ripple occurs in the electric motor.

Further, in the above-mentioned prior art, since there is a detection delay in the detection of the output current and a control delay until the actual voltage is output from the voltage command, the waveform distortion is not compensated correctly and the output voltage waveform is not compensated. However, there is a problem that a torque ripple is generated in the electric motor because it does not become a sine wave.

An object of the present invention is to correct the output voltage waveform distortion of the PWM inverter correctly to make the output voltage waveform a sine wave and suppress the torque ripple generated in the electric motor.

[0007]

Means for Solving the Problems The above-mentioned object is provided with means for judging the detection of the polarity of an output current as three modes of positive / negative and intermittent mode in which the polarity changes with each switching.
When the output current is in the intermittent mode, it can be achieved by setting the compensation voltage of the phase to zero.

The above object can also be achieved by providing means for advancing the phase of the output current detection signal by a predetermined value.

[0009]

The distortion voltage due to the dead time that prevents the switching element of the voltage source inverter from being short-circuited is determined by the polarity of the output current. When the output current is positive, the distortion voltage of the phase is positive, and when the output current is negative. Causes the distortion voltage of the phase to become negative,
The absolute value of the strain voltage is almost constant regardless of the magnitude of the output current.

However, the output current of the inverter is PW
Since the current ripple due to the M control is included, the polarity of the output current changes between positive and negative during the period when the output current is near zero, so that the average distortion voltage becomes zero or a value close to zero.

Therefore, the polarity of the output current is detected, and the compensation voltage is positive when the output current is positive, negative when the output voltage is negative, and negative when the output current is intermittent. Is set to zero or a value close to zero, the compensating voltage can be brought close to the distortion voltage, the output voltage waveform can be made a sine wave, and the torque ripple generated in the motor can be suppressed. However, if there is a detection delay when detecting the output current or a control delay from when the voltage command is calculated until the actual current is output, a delay occurs in the compensation voltage and output voltage distortion compensation is performed correctly. Absent. Therefore, by performing phase lead compensation that advances the phase of the output current detection signal, the output current distortion can be compensated correctly.

In order to advance the phase of the output current detection signal, the fact that the three-phase current signals have a phase difference of 120 degrees with each other is utilized, and it is realized by adding the three-phase output current detection signals at a predetermined ratio. it can.

Further, paying attention only to the vicinity of the zero cross of the output current detection signal, and advancing the phase of only that portion, a predetermined positive signal is added at the rise of the output current detection signal and the fall of the output current detection signal. This can sometimes be achieved by adding a predetermined negative signal.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a first embodiment using the present invention. In FIG. 1, 1 is a PWM inverter that converts a DC voltage into an AC voltage, and 2 is an induction motor that is connected to the AC output terminals of each phase U, V, W of the inverter 1. Reference numeral 3 is an integrator circuit for instructing the phase reference ω1t from the primary angular frequency command ω1 * of the induction motor 2, and 4 is an oscillator that outputs a sine wave signal having a constant amplitude and a frequency proportional to the output signal from the integrator circuit 3. Then, the output signal is applied to the coordinate converter 7. Reference numeral 5 is a voltage calculation circuit that outputs a voltage command vd * for the electric motor 2 in accordance with the exciting current command signal id *, 6
Is a voltage calculation circuit that outputs a voltage command vq * of the electric motor 2 according to the torque current command signal iq *, and 7 is a voltage command vd
*, Vq * are voltage commands vu *, vv *, vw * of the stator coordinates from the rotating magnetic field coordinates based on the sine wave signal of the oscillator 4.
It is a coordinate converter that converts to. 81, 82, 83 are PW
A current detector for detecting the output currents iu, iv, iw of the M inverter 1, 9 is a current detection signal iu, iv, iw
Is a phase advance compensating circuit for converting into signals iu ', iv', iw 'which are advanced by a predetermined phase. Reference numerals 11, 12, 13 denote polarities of output signals iu', iv ', iw' of the phase advance compensating circuit 9, respectively. / Negative / intermittent, and based on this, a compensation voltage calculation circuit that outputs compensation voltages vfu, vfv, vfw for compensating the output voltage distortion due to the dead time of the inverter. Reference numerals 21, 22 and 23 denote stator coordinate voltage commands vu *, vv *, vw * and compensation voltages vfu, vfv,
An adder for adding vfw, 10 is adders 21, 22, 2
3 output signals vu * + vfu, vv * + vfv, vw *
This is a PWM pulse generation circuit that compares + vfw with a carrier signal for pulse width modulation and generates PWM signals Pu, Pv, Pw for turning on and off the switching elements forming the PWM inverter 1.

The basic operation of this embodiment is as follows. As is well known, this control system is a control system of the induction motor 2 called vector control by a PWM inverter, and the voltage command vd of the induction motor 2 is calculated from the exciting current command signal id * and the torque current command signal iq * of the rotating magnetic field coordinate system.
*, Vq * are calculated, and the voltage command vu *, vv *, vw * of the sine wave obtained by converting this voltage command from the rotating magnetic field coordinate system to the stator coordinate system based on the output sine wave signal of the oscillator 4 is the carrier signal. The output voltage of each phase is controlled according to the PWM signal obtained by comparison with. On the other hand, the compensation of the voltage drop due to the dead time of the PWM inverter 1 is feedforward compensated by the signal from the compensation voltage calculation circuit in the stator coordinate system.

Next, a method of compensating for a voltage drop due to dead time will be described.

FIG. 2 is a block diagram showing a model of voltage distortion due to dead time of the PWM inverter and dead time compensation according to the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals. In this model, P
The harmonic voltage due to the WM pulse is ignored. The PWM pulse generation circuit 10 inputs the added value of the voltage command v * and the compensation voltage vf, and performs PWM through the delay of the control delay time Td1.
Output to the inverter 1. PW in the PWM inverter 1
From the output signal of the M pulse generation circuit 10, the voltage v obtained by subtracting the distortion voltage Δv corresponding to the motor current (inverter output current) i is output. In the induction motor 2, a current i corresponding to the inverter output voltage v flows. The current detector 81 detects the motor current i and outputs it after a delay of the detection delay time Td2. The phase lead compensating circuit 11 inputs the detected current signal i and outputs an output signal i ′ advanced by a predetermined phase. The compensation voltage calculation circuit 21 calculates the compensation voltage vf based on the polarity of the output signal i ′ of the phase advance compensation circuit 11.

FIG. 3 shows the inverter output current i and the distortion voltage Δ.
The operation | movement waveform of v and compensation voltage vf is shown. When the inverter output current i is positive, the distortion voltage Δv is positive, when the inverter output current i is negative, the distortion voltage Δv is negative, but when the inverter output current i is intermittent due to ripple, the distortion voltage Δv is average. Is almost zero. The effect of the distortion voltage can be compensated by adding a voltage for canceling the distortion voltage Δv to the voltage command signal input to the inverter. Therefore, the compensation voltage signal vf output from the compensation voltage calculation circuit 21 is the distortion voltage Δ.
It suffices to use a signal that leads v by the control delay time Td1. Therefore, the phase lead compensation circuit 11 includes Td1 + Td for the detected current including the detection delay time Td2.
The signal advanced by 2 is used as the output signal i '.

Current signals iu, iv, iw on the stator coordinates
Is converted to signals iu ′, iv ′, iw ′ obtained by advancing the phase ψ by the following equation.

[0020]

[Equation 1]

Here, the advanced phase ψ is the detection delay time Td.
1, based on the control delay time Td2 and the primary angular frequency command ω1 *, the value is expressed by the following equation.

[0022]

[Equation 2]

FIG. 4 shows the configuration of the phase lead compensation circuit 9.
The amplifier 91 calculates the primary angular frequency command ω1 according to the equation (2).
The lead compensation phase ψ based on * is output. Function generator 9
2 is a multiplication coefficient cos ψ, cos (ψ based on the lead compensation phase ψ
+ 2 / 3π), cos (ψ-2 / 3π) are output. The multipliers 931 to 953 and the adders 961 to 963 have current detection signals iu, iv, iw and multiplication coefficients cos ψ, cos (ψ + 2 //
3π), cos (ψ-2 / 3π) according to the equation (Equation 1),
Detected current signals iu ', iv', iw 'with phase lead compensation
Is output.

FIG. 5 shows the configuration of the compensation voltage calculation circuit 11. The comparator 111 detects the phase lead compensated detection current signal i.
It outputs the instantaneous polarity signal Su of u '. The D-flip-flop circuit 112 outputs a polarity signal Q1u obtained by sampling the instantaneous polarity signal Su at the rising edge of Pu using the PWM signal Pu for turning on and off the switching element forming the PWM inverter 1 as a clock signal, and D The flip-flop circuit 113 outputs a polarity signal Q2u which is a sample of the instantaneous polarity signal Su at the falling edge of Pu using the inverted signal of the PWM signal Pu as a clock signal. The compensation voltage selection circuit 115 outputs the compensation voltage vfu based on the polarity signals Q1u and Q2u.

Next, the operation of the compensation voltage selection circuit 115 will be described with reference to FIG.
Will be explained. Since the ripple due to the PWM voltage occurs in the inverter output current, the detected current signal iu ′ is at the minimum value of the ripple when the PWM signal Pu rises, and the detected current signal i when the PWM signal Pu falls.
u ′ is the maximum value of ripple. Therefore, as shown in FIG. 6, when both the polarity signals Q1u and Q2u are at the H level, the polarity of the detection current signal iu 'is positive, and the polarity signal Q1
When u and Q2u are both at the L level, the detected current signal i
The polarity of u'is determined to be negative. When the polarity signal Q1u is at the L level and Q2u is at the H level, the detected current signal i
u'is determined to be in the intermittent mode. Maximum ripple
Due to the minimum relationship, in principle, the state where the polarity signal Q1u is at L level and Q2u is at H level does not occur.

The compensation voltage selection circuit 115 has a polarity signal Q1.
Compensation voltage vfu is output based on u and Q2u. Q1
When u and Q2u are both at the H level, + Vf is output as the compensation voltage vfu, when both Q1u and Q2u are at the L level, -Vf is output as the compensation voltage vfu, and when Q1u is at the L level and Q2u is at the H level, zero is output. Compensation voltage v
Output as fu.

According to this embodiment, there is provided means for judging the polarity of the PWM inverter output current as three modes of the positive / negative and the intermittent mode in which the polarity changes each time the switching is performed. By making the phase compensation voltage close to zero, the output voltage waveform distortion of the PWM inverter can be compensated correctly. Further, according to the present invention, by providing means for advancing the phase of the output current detection signal by a predetermined value, the output current detection delay and the output voltage control delay are compensated, and the output voltage waveform distortion of the PWM inverter is compensated. Can be done correctly. By correctly compensating for the output voltage waveform distortion of the PWM inverter, it is possible to make the output voltage waveform a sine wave and suppress the torque ripple generated in the electric motor.

FIG. 7 is a diagram showing a second embodiment using the present invention. Since the same elements as those in FIG. 1 are designated by the same reference numerals, the description thereof will be omitted. The difference from FIG. 1 is that a current detection correction signal is calculated from the current command signal and is added to the output current detection signal to correct the output current detection delay and the output voltage control delay.

In FIG. 7, 14 is an exciting current command id *.
And a torque current command iq *, a divider 15 is an arctangent function circuit that calculates the torque angle Δθi from the ratio of the exciting current command id * and the torque current command iq *, and 16 is a phase reference ω.
An adder for calculating the current phase θi by adding 1t and the torque angle Δθi, and 17 is a current detection correction signal Δiu for advancing the phase of the output current detection signal of each phase from the current phase θi,
Correction current calculation circuit for calculating Δiv, Δiw, 18 to 2
Reference numeral 0 is an adder for adding the current detection correction signals Δiu, Δiv, Δiw to the output current detection signals iu, iv, iw.

FIG. 8 is a diagram showing the configuration of the correction current calculation circuit 17. The function generator 171 outputs the cosine wave signals cos θi, cos (θi−2 / 3π), cos (θi) based on the current phase θi.
-4 / 3π) is output. Polarity detectors 172, 173
174 and multipliers 175, 176, 177 obtain square wave current detection correction signals Δiu, Δiv, Δiw with an amplitude ΔI and a phase advanced by 90 ° from the AC current signal. The amplitude ΔI of the current detection correction signal is given by the following equation from the effective value command I * of the fundamental current, the primary angular frequency command ω1 *, and the advance time ΔT.

[0031]

[Equation 3]

FIG. 9 is an operation waveform diagram showing the operation of correcting the phase lead of the output current detection signal in the second embodiment of the present invention shown in FIG. In FIG. 9, (a) is the U-phase current detection signal iu. (B) is the U-phase current detection correction signal Δiu, which is a square wave with a 90 ° phase advance with respect to iu. (C) is a correction current detection signal iu ′ obtained by adding iu and Δiu, and the timing of the zero cross is advanced with respect to iu by the time ΔT. (D) is the output vfu of the compensation voltage calculation circuit 11 with iu 'as input.

According to the present invention, there is provided means for determining the polarity of the PWM inverter output current as three modes of positive / negative and intermittent, in which the polarity changes with each switching. When the output current is in the intermittent mode, the phase is detected. The output voltage waveform distortion of the PWM inverter can be compensated correctly by setting the compensation voltage of to near zero. Further, according to the present invention, by providing means for advancing the phase of the output current detection signal by a predetermined value, the output current detection delay and the output voltage control delay are compensated, and the output voltage waveform distortion of the PWM inverter is compensated. Can be done correctly. By correctly compensating for the output voltage waveform distortion of the PWM inverter, it is possible to make the output voltage waveform a sine wave and suppress the torque ripple generated in the electric motor.

[0034]

According to the present invention, there is provided means for judging the polarity of the PWM inverter output current as three modes of positive / negative and intermittent which changes the polarity for each switching, and when the output current is in the intermittent mode. By making the compensation voltage of the phase close to zero, the output voltage waveform distortion of the PWM inverter can be compensated correctly. Further, according to the present invention, by providing means for advancing the phase of the output current detection signal by a predetermined value, the output current detection delay and the output voltage control delay are compensated, and the output voltage waveform distortion of the PWM inverter is compensated. Can be done correctly. By correctly compensating for the output voltage waveform distortion of the PWM inverter, it is possible to make the output voltage waveform a sine wave and suppress the torque ripple generated in the electric motor.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing a model of voltage distortion due to dead time and its compensation.

FIG. 3 is an operation waveform diagram of an inverter output current, a distortion voltage, and a compensation voltage.

FIG. 4 is a configuration diagram of a phase lead compensation circuit.

FIG. 5 is a configuration diagram of a compensation voltage calculation circuit.

FIG. 6 is a diagram showing an operation of a compensation voltage selection circuit.

FIG. 7 is a configuration diagram of a second embodiment of the present invention.

FIG. 8 is a configuration diagram of a correction current calculation circuit.

FIG. 9 is a diagram showing an operation of phase lead correction in the second embodiment of the present invention.

[Explanation of symbols]

1 ... PWM inverter, 2 ... Induction motor, 7 ... Coordinate converter, 9 ... Phase advance compensation circuit, 10 ... PWM pulse generation circuit, 11-13 ... Compensation voltage calculation circuit, 81-83 ... Current detector.

Claims (2)

[Claims] 1. An inverter device for supplying an alternating current of variable voltage and variable frequency to an induction motor, which detects an output current of an inverter and performs a phase lead correction for advancing a phase of a current detection signal by a predetermined value to obtain a corrected current. The polarity of the detection signal is judged as three modes of positive / negative / intermittent, and the voltage command correction signal of positive / negative / zero is calculated for positive / negative / intermittent of the polarity signal to correct the voltage command. Characteristic voltage source inverter device. 2. An inverter device for supplying an alternating current of a variable voltage variable frequency to an induction motor, wherein an output current of the inverter is detected, and an addition signal of this current detection signal and a bias signal obtained from a phase signal of the alternating current signal is detected. The polarity of the obtained correction current detection signal is determined as three modes of positive / negative / intermittent, and a positive / negative / zero voltage command correction signal is calculated for the positive / negative / intermittent polarity signal, and the voltage is calculated. A voltage source inverter device characterized by correcting a command.