JPH0720384B2 - Voltage source inverter control method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling an inverter, and more particularly to controlling a voltage source inverter suitable for controlling the output voltage of a voltage source pulse width modulation inverter. A method and an apparatus thereof.

[Conventional technology]

In the PWM inverter, a method is adopted in which the positive side and the negative side switching elements forming the inverter are alternately conductively controlled to control the output voltage by PWM. When performing such a control method, since there is a switching delay due to the turn-off time in the switching element, a short-circuit prevention period (hereinafter referred to as on-delay) so that the positive-side and negative-side switching elements do not conduct at the same time. ) Is provided. However, there is a problem that the output voltage of the inverter is lowered by the on-delay, and the output voltage of the inverter is distorted.

Therefore, conventionally, as a method of compensating for the output voltage distortion due to on-delay, as disclosed in Japanese Patent Laid-Open No. 60-82066, there is a method of detecting the output voltage of the inverter and generating a pulse width. Proposed. Further, as described in JP-A-62-135289, the output voltage drop due to the on-delay of the inverter is calculated based on the output current command signal, and this calculated value is added to the output voltage command of the inverter to obtain the on-delay. Methods have been proposed to compensate for the accompanying output voltage drop.

[Problems to be Solved by the Invention]

However, the above-mentioned conventional technique requires a detector for detecting the output voltage of the inverter, and the hardware configuration becomes complicated. Moreover, since a constant value is added to the output voltage command of the inverter, even if the magnitude of the output voltage drop due to the on-delay changes depending on the magnitude of the inverter output current, this cannot be compensated. There's a problem.

It is an object of the present invention to provide a voltage source inverter control method and apparatus capable of compensating an output voltage drop due to on-delay according to the magnitude of an inverter output current without detecting an output signal of the inverter. .

[Means for Solving the Problems]

In order to achieve the above object, the present invention, as a first control method, calculates the magnitude of an inverter output current from an excitation current command signal and a torque current command signal for an AC motor of an inverter load, and calculates the primary of the AC motor. Calculate the phase angle of each phase of the inverter output current from the coordinate reference signal and each command signal obtained from the angular frequency command signal, and calculate the AC current command signal of each phase from the magnitude of the inverter output current and the phase angle of each phase. Generates the on-delay compensation voltage of each phase according to the magnitude and polarity of this AC current command signal, and then calculates the AC voltage command of each phase of the stator coordinate system obtained from the voltage command signal of the rotating magnetic field coordinate system of the AC motor. Each of the on-delay compensation voltages is added to the signal to generate the output voltage command signal of each phase, and the on-delay is added to these signals to generate the pulse-width modulated signal, It is obtained by employing the control method of the voltage source inverter for controlling the inverter by No..

As a second control method, the magnitude of the inverter output current is calculated from the excitation current command signal and the torque current command signal for the AC motor of the inverter load, and the magnitude of the inverter output current and the voltage drop of the inverter due to the on-delay are almost constant. The phase angle common to each phase is calculated from the ratio with the magnitude of the inverter output current obtained as
The phase angle of each phase of the inverter output current is calculated from the coordinate reference signal obtained from the primary angular frequency command signal of the AC motor and each of the command signals, and the calculated current phase angle of each phase and the current phase common to each phase The on-delay compensation voltage of each phase whose magnitude and polarity are determined according to the angle is generated, and each on-delay is added to the alternating-current voltage command signal of each phase of the stator coordinate system obtained from the voltage command signal of the rotating magnetic field coordinate system of the AC motor. Compensation voltage is added to generate output voltage command signals for each phase, pulse width modulation signals are generated by adding on-delay to these signals, and the inverter is controlled by each pulse width modulation signal. It was adopted.

As a first control device, a voltage for calculating an excitation current command signal for an AC motor of an inverter load, a voltage command signal for each phase of a rotating magnetic field coordinate system of the AC motor based on a torque current command signal and a primary angular frequency command signal. Command calculator,
A coordinate converter that converts the output signal of the voltage command calculator into an AC voltage command signal for each phase of the stator coordinate system of the AC motor according to the coordinate reference signal obtained from the primary angular frequency command signal,
In the controller of the voltage source inverter, which has a pulse width modulation signal that adds on-delay to the output signal of each phase of the coordinate converter and controls the inverter by this signal, the excitation current command signal and the torque current A current calculator that calculates the magnitude of the inverter output current from the command signal, a phase angle calculator that calculates the phase angle of each phase of the inverter output current from the coordinate reference signal, the excitation current command signal, and the torque current command signal, and the current An AC current command signal generator that generates an AC current command signal for each phase from the output signal of the calculator and the output signal of the phase angle calculator, and an on-delay compensation voltage for each phase according to the magnitude and polarity of the AC current command signal. Control of voltage source inverter provided with compensating voltage generator for outputting and adder for adding each output signal of compensating voltage generator to output signal of coordinate converter One in which you configure the location.

As a second control device, a voltage for calculating a voltage command signal for each phase of the rotating magnetic field coordinate system of the AC motor based on the excitation current command signal, the torque current command signal, and the primary angular frequency command signal for the AC motor of the inverter load. Command calculator,
A coordinate converter that converts the output signal of the voltage command calculation unit into an AC voltage command signal of each phase of the stator coordinate system of the AC motor according to the coordinate reference signal obtained from the primary angular frequency command signal,
In the controller of the voltage source inverter, which has a pulse width modulation signal that adds on-delay to the output signal of each phase of the coordinate converter and controls the inverter by this signal, the excitation current command signal and the torque current A current calculator that calculates the magnitude of the inverter output current from the command signal, and a first phase angle calculator that calculates the phase angle of each phase of the inverter output current from the coordinate reference signal, the exciting current command signal, and the torque current command signal. A second phase angle calculation for calculating a phase angle common to each phase from the ratio between the output signal of the current calculator and the magnitude of the inverter output current obtained as a current when the voltage drop of the inverter due to on-delay becomes almost constant And a compensation voltage calculator for calculating the on-delay compensation voltage of each phase whose magnitude and polarity are determined from the output signal of each phase angle calculator, and It is obtained by constituting the control apparatus of the voltage source inverter provided with an adder for adding the output signal of the pressure calculating unit on the output signal of the coordinate converter.

[Action]

As shown in FIG. 3, the output voltage drop due to the on-delay with respect to the magnitude of the output current of the PWM inverter changes its polarity according to the polarity of the output current, and its characteristics are a region I where the output current is small and a region where the output current is large. It is divided into II. Therefore, the output voltage drop with respect to the AC output current of the inverter changes according to the magnitude of the output current, as shown in FIG. Therefore, the compensation voltage is calculated according to the magnitude of the output current, and the compensation voltage can be compensated for by adding the compensation voltage to the three-phase AC voltage command signal of the stator coordinate system of the AC motor. It will be possible. The magnitude of the compensating voltage is determined according to the magnitude of the output current, and when the compensating voltage compensates the voltage drop due to on-delay, the error voltage becomes zero, and it is possible to prevent trip ripple from occurring in the AC motor. It will be possible.

〔Example〕

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

In FIG. 1, the PWM inverter 1 includes three sets of transistors as positive side and negative side switching elements, receives a pulse width modulation signal from the PWM pulse calculator 9 and converts a DC voltage into a three-phase AC voltage. Then, the converted three-phase AC voltage is supplied to the induction motor 2. The speed of the induction motor 2 is detected by the speed detector 3, and the speed signal ωγ which is the detection output of the speed detector 3 is supplied to the adders 4 and 11. The speed signal ωγ and the speed command signal ωγ * are supplied to the adder 4, and a signal corresponding to the deviation of each signal is supplied to the speed adjuster 5. The regulator 5 is a torque current command signal for suppressing the output signal of the adder 4 to zero.
It is designed to output Iq *. Torque current command signal
Iq * is supplied to the voltage command calculator 6, the slip angular frequency calculator 10, and the compensation voltage calculator 13, and the slip angular frequency calculator 10 receives the excitation current command signal Id * and the torque current command signal Iq *.
The slip angular frequency signal ωs * is calculated, and the calculated signal is output to the adder 11. The adder 11 adds the signal ωs * and the speed ωγ to generate a primary angular frequency command signal ω ₁ *, and uses this signal as a voltage command calculator 6 and an integrator.
It is designed to output to 12. The integrator 12 outputs the signal ω ₁ *
Is integrated over time to generate a coordinate reference signal ω ₁ t, and this signal is output to the compensation voltage calculator 13 and the coordinate converter 7.

The voltage command calculator 6 uses the excitation current command signal Id *, the torque current command signal Iq *, and the primary angular frequency command signal ω ₁ * to generate voltage command signals Vd *, V in the rotating magnetic field coordinate system of the induction motor 2.
It is designed to calculate q *. Each voltage command signal is obtained by the following equations (1) and (2).

Vd * = γ ₁ · Id * −ω ₁ * (l ₁ + l ₂ ′) · Iq *… (1) Here, γ ₁ : primary resistance value l ₁ , l ₂ ′: primary and secondary leakage inductance value M: exciting inductance value T ₂ : secondary time constant s: differential operator.

The coordinate converter 7 receives the voltage command signals Vd *, Vq * and the coordinate reference signal ω ₁ t, and outputs the voltage command signals Vd *, Vq * according to the coordinate reference signal ω ₁ t in the stator coordinate system of the electric motor 2. It is adapted to be converted into a phase AC voltage command signal V *. This command signal V * is added by the adder 8 to the compensation voltage Vf from the compensation voltage calculator 13.
* (Vfu *, Vfv *, Vfw *) is added and converted into an output voltage command signal V **. Output voltage command signal V ** is PWM
It is supplied to the pulse calculator 9 and compared with the carrier signal to be converted into a pulse width modulation signal. When the pulse width modulation signal is generated, the pulse width modulation signal is generated by adding an on-delay for preventing the positive side and the negative side transistors of the PWM inverter 1 from conducting at the same time. Switching of each transistor of the PWM inverter 1 is controlled by this pulse width modulation signal, and the DC voltage is converted into a three-phase AC voltage.

The three-layer AC voltage command signal V * (Vu *, Vv *, Vw *) is expressed by the following equation (3).

The compensation voltage calculator 13 calculates the compensation voltage Vf based on the excitation current command signal Id *, the torque current command signal Iq *, and the coordinate reference signal ω ₁ t.
It is configured to calculate *, and its specific configuration is shown in FIG.

Compensation voltage calculator 13 is current calculator 14, arctangent calculator 15, constant generator 16, adders 17,18, cosine calculators 20,21,22, multipliers 23,24,25, function generator 26, It is composed of 27 and 28.
The current calculator 14 uses the excitation current command signal Id * and the torque current command signal Iq * to calculate the output current magnitude Im according to the following equation (4).
* Is calculated and the calculation result is output to the multipliers 23, 24, 25.

The arctangent calculator 15 calculates the current phase angle θ * from the command signals Id *, Iq * according to the following equation (5), and the calculation result is added by the adder 17
It is designed to output to.

θ * = tan ⁻¹ (Iq * / Id *) (5) The adder 17 adds the current phase angle θ * and the coordinate reference signal ω, t to generate the U-phase current phase angle θiu *. This signal is output to the adder 18 and the cosine calculator 20. The output signal of the cosine calculator 20 is output from the multiplier 23 as the magnitude of the output current Im.
It is multiplied by * and converted into a sinusoidal AC current command iu *.

On the other hand, the adder 18 includes a current phase angle θiu * and a constant generator 16
Is supplied with a signal for shifting the phase angle by 2π / 3, the adder 18 outputs the V-phase current phase angle θiv *, and this signal is supplied to the multiplier 24 via the cosine multiplier 21. To be done. Then, from the multiplier 24, the V-phase AC current command signal Iv
* Is generated. Further, the adder 19 is supplied with the signal from the constant generator 16 and the signal of the current phase angle θiv * from the adder 18. From this adder 19, the W-phase current phase angle θiw
The * signal is output, and this signal is supplied to the multiplier 25 via the cosine calculator 22. Then, the W-phase AC current command iw * is generated from the multiplier 25. AC current command signals iu *, iv *, iw * of each phase are output from the multipliers 23, 25 to the function generators 26, 2
When applied to 7, 28, on-delay compensation voltages Vfu *, Vfv *, Vfw * corresponding to the magnitude and polarity of each command signal are output.

The function generators 26, 27, 28 are composed of memories, and various on-delay compensation voltages are stored at addresses corresponding to the alternating current command. When storing this on-delay compensation voltage, as shown in FIG. 3, under the condition that the primary side frequency command signal ω ₁ * = 0 and the voltage command signal Vq * = 0
The PWM inverter 1 is operated, the relationship between the output current i and the voltage drop Vf is measured, and the on-delay compensation voltage according to the measurement result is stored. Therefore, when the alternating current command that matches the actual current is generated, the on-delay compensation voltage corresponding to the magnitude of the alternating current command is selected, and the function generators 26, 27, and 28 display in FIG. As shown, the compensation voltage Vf * corresponding to the magnitude of the output current i is output. When this compensation voltage Vf * is added to the AC voltage command signal V *, the output voltage command signal V ** is output as a signal as shown in FIG.

As described above, in this embodiment, the on-delay compensation voltage Vf * according to the magnitude of the output current i is added to the three-phase AC voltage command signal V *, so that the output current of the inverter 1 is distorted in waveform. Can be suppressed, and torque ripple can be prevented from occurring in the induction motor 2.

Next, another embodiment of the present invention will be described with reference to FIG.

In this embodiment, instead of obtaining the AC current command signal, the magnitude of the on-delay compensation voltage is directly calculated from the phase angle of the output current, and the compensation voltage calculator 13 has a cosine calculator 20, 21,22, multipliers 23,24,25, function generators 26,27,
Instead of 28, phase angle calculator 29, compensation voltage calculator 30, 31, 32
Is provided.

In the present embodiment, as shown in FIG. 3, paying attention to the fact that a portion of the output voltage drop due to on-delay that is proportional to the magnitude of the output current i becomes a compensation error, and the moment when the AC current command signal is instantaneously generated. Instead, the on-delay compensation voltage with respect to the phase angle of the output current is obtained. That is, in the range of the output current i is ± ic, the output voltage drop due to on-delay is proportional to the output current i, and when it is ± ic or more, the output voltage drop is constant. Therefore, assuming that the current changes with Im * sin (ω ₁ t), if we recapture this with the phase angle,
In the range of the phase angle ± sin ^-1 (ic / Im *), the output voltage drop due to on-delay changes according to a linear function, and is constant in other cases.

Here, if the phase angle θc * = sin ⁻¹ (ic / Im *) common to each phase, θc * is expressed by the following equation (6), and is calculated by the phase angle calculator 29.

The output signal θc * of the phase angle calculator 29 is the current phase angle θ of each phase.
It is supplied to the compensation voltage calculators 30, 31, and 32 together with iu *, θiv *, and θiw *. The compensation voltage calculators 30, 31, 32 are based on the phase angles, and the on-delay compensation voltages Vfu *, Vfu of each phase are supplied. *, Vfw *
Is calculated and the calculation result is output to the adder 8. Then, each computing unit 30, 31, 32 determines the polarity of each phase from the current phase angle of each phase among the phase angles.
That is, from the property of the cosine function, It is decided to be positive in the range of, and negative otherwise. When calculating the on-delay compensation voltage from each phase angle, the processing shown in FIG. 7 is performed.
Since the calculation processing of the on-delay compensation voltage for each phase is the same, only the U phase will be described.

First, a limiting process is performed so that the current phase angle θiu * is always in the range of ± π (step 30A), and after this process, the polarities are determined in steps 30B, 30C and 30D. That is, in step 30B, the current phase angle θiu * is changed from the property of the cosine function. It is judged whether it is within the range of Within the range, Sgn (sign) is set to 1, and otherwise, Sgn is set to -1.

Next, θiu * When the U-phase current changes from one side to the + side and is near the zero point, it is determined whether the range is ± θc *. In this case, in order to compare with θc *, Has been added. When it is determined in step 30E that the U-phase current is near the first zero point and is within the range of ± θc *, the magnitude coefficient k is obtained in step 30F.

On the other hand, θiu * When the U phase current changes from the + side to the − side and is near the zero point, it is determined whether or not the range is ± θc * (step 30G). In this case, in order to compare θiu * with θc * Is subtracted. Then, in step 30G, the U-phase current is the second
If it is determined to be in the vicinity of the zero point of and within the range of ± θc *, the coefficient of magnitude k is obtained in step 30H. When it is determined that the U-phase current is within the range at 30G, the coefficient k is processed as 1 (step 30A).

After the coefficient k is obtained in steps 30F, 30H and 30I, the on-delay compensation voltage Vfu * is obtained in the following equation (7) in step 30J.

Vfu * = k · Vf · Sgn (7) Here, Vf represents a value at which the output current i is substantially constant among the magnitudes of the voltage drops due to the on-delay shown in FIG.

According to the present embodiment, the ON-delay compensation voltage according to the magnitude of the output current is added to the three-phase AC voltage command signal as in the above-described embodiment, so that the waveform distortion of the output current of the inverter is suppressed. Therefore, it is possible to prevent the triple ripple from occurring in the induction motor. Further, since a calculator and a function generator for calculating the alternating current command signal are not required, the calculation by digital control becomes easier than that in the above embodiment.

〔The invention's effect〕

As described above, according to the present invention, the output voltage drop due to the on-delay of the inverter is compensated according to the magnitude of the output current of the inverter. Therefore, the output of the inverter is not affected by the magnitude of the output current of the inverter. It is possible to suppress the waveform distortion of the current and prevent the torque ripple from being generated from the AC motor of the inverter load.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIG. 2 is a specific configuration diagram of a compensation voltage calculator, FIG. 3 is a characteristic diagram showing a relationship between output current and output voltage drop, and FIG. FIG. 6 is a characteristic diagram showing the characteristics of the on-delay compensation voltage according to the magnitude of the output current, FIG. 5 is a waveform diagram of the output voltage command signal, and FIG. 6 is a compensation voltage calculator of another embodiment of the present invention. Specific configuration diagram,
FIG. 7 is a flow chart for explaining the processing contents of the arithmetic unit shown in FIG. 1 ... PWM inverter, 2 ... Induction motor, 3 ... Speed detector, 4,8,11 ... Adder, 5 ... Speed controller, 6 ... Voltage command calculator, 7 ... Coordinate converter , 9 ... PWM pulse calculator, 10 ... Slip angular frequency calculator, 12 ... Integrator, 13 ... Compensation voltage calculator.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Takahashi 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture, Ltd. Omika Plant, Hitachi, Ltd. (56) Reference JP-A-64-60264 (JP, A)

Claims (4)

[Claims] 1. A coordinate reference signal obtained from a primary angular frequency command signal of an AC motor and the coordinate reference signal obtained by calculating the magnitude of an inverter output current from an exciting current command signal and a torque current command signal for an AC motor of an inverter load. The phase angle of each phase of the inverter output current is calculated from the command signal, and the AC current command signal of each phase is generated from the magnitude of the inverter output current and the phase angle of each phase, depending on the size and polarity of this AC current command signal. Then, the on-delay compensation voltage of each phase is obtained, and the on-delay compensation voltage of each phase is added to the alternating-current voltage command signal of each phase of the stator coordinate system obtained from the voltage command signal of the rotating magnetic field coordinate system of the AC motor. A voltage source inverter that generates output voltage command signals, generates pulse width modulation signals by adding on delay to these signals, and controls the inverter by each pulse width modulation signal. Control method. 2. The magnitude of the inverter output current is calculated from the exciting current command signal and the torque current command signal for the AC motor of the inverter load, and the magnitude of the inverter output current and the voltage drop of the inverter due to the on-delay become substantially constant. The phase angle common to each phase is obtained from the ratio with the magnitude of the inverter output current obtained as the current, and the inverter output current is obtained from the coordinate reference signal obtained from the primary angular frequency command signal of the AC motor and the respective command signals. The phase angle of each phase is calculated, and the on-delay compensation voltage of each phase whose magnitude and polarity are determined according to the calculated current phase angle of each phase and the common current phase angle of each phase is generated, and the rotating magnetic field coordinates of the AC motor are calculated. Output voltage command signal of each phase by adding each on-delay compensation voltage to the AC voltage command signal of each phase of the stator coordinate system obtained from the voltage command signal of the system Generated, it generates a pulse width modulated signal obtained by adding Onderei to these signals, the control method of the voltage source inverter for controlling the inverter by the pulse width modulated signal. 3. A voltage command calculation for calculating a voltage command signal for each phase of a rotating magnetic field coordinate system of an AC motor based on an exciting current command signal for an AC motor of an inverter load and a torque current command signal and a primary angular frequency command signal. Converter, a coordinate converter for converting the output signal of the voltage command calculator into an AC voltage command signal for each phase of the stator coordinate system of the AC motor according to the coordinate reference signal obtained from the primary angular frequency command signal, and coordinate conversion In the control device of the voltage source inverter, which has a pulse width modulation signal in which on-delay is added to the output signal of each phase of the voltage generator, and the inverter is controlled by this signal, the excitation current command signal and the torque current command signal A current calculator that calculates the magnitude of the inverter output current from the
A phase angle calculator that calculates the phase angle of each phase of the inverter output current from the coordinate reference signal, the excitation current command signal, and the torque current command signal, and the output signal of the current calculator and the output signal of the phase angle calculator The AC current command signal generator that generates the AC current command signal, the compensation voltage generator that outputs the on-delay compensation voltage of each phase according to the magnitude and polarity of the AC current command signal, and the output signals of the compensation voltage generator A control device for a voltage source inverter, comprising: an adder for adding the output signal of the coordinate converter. 4. A voltage command calculation for calculating a voltage command signal for each phase of a rotating magnetic field coordinate system of the AC motor based on an exciting current command signal, a torque current command signal and a primary angular frequency command signal for an AC motor of an inverter load. And a coordinate converter for converting the output signal of the voltage command calculation unit into an AC voltage command signal for each phase of the stator coordinate system of the AC motor according to the coordinate reference signal obtained from the primary angular frequency command signal, and coordinate conversion In the control device of the voltage source inverter, which has a pulse width modulation signal in which on-delay is added to the output signal of each phase of the voltage generator, and the inverter is controlled by this signal, the excitation current command signal and the torque current command signal A current calculator that calculates the magnitude of the inverter output current from the
The first phase angle calculator that calculates the phase angle of each phase of the inverter output current from the coordinate reference signal, the excitation current command signal, and the torque current command signal, and the output signal of the current calculator and the voltage drop of the inverter due to on-delay A second phase angle calculator that calculates the phase angle common to each phase from the ratio of the magnitudes of the inverter output currents obtained as constant currents, and the magnitude and polarity are determined from the output signals of each phase angle calculator A compensation voltage calculator for calculating the on-delay compensation voltage of each phase,
A voltage source inverter control device, comprising: an adder that adds each output signal of the compensation voltage calculator to the output signal of the coordinate converter.