JPS59159687A - Controlling method and device of pwm inverter - Google Patents

Abstract

PURPOSE:To reduce the noise irrespective of a load state by regulating the gain of a current control system of a PWM inverter proportional to the speed of an AC motor and reducing the ripple of a sinusoidal voltage command signal at the low speed time. CONSTITUTION:A deviation beteen a speed detection signal and a speed command signal of an AC motor 2 is applied to a current instructing circuit 13 to obtain a sinusoidal current command signal, compared with a current detection signal and applied to a multiplier 19. On the other hand, a signal proportional to the speed detection signal is generated from a gain setter 18, inputted to the multiplier 19, the output is compared with a triangular signal T of an oscillator 16 to control a PWM inverter 1, thereby driving a motor 2. Accordingly, the gain of a current control system is automatically regulated in proportion to the rotating speed by the setter 18 to reduce the ripple component contained in a sinusoidal voltage command signal at the low speed operation time, thereby reducing the magnetic sound generated from the motor 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for controlling a PWM inverter that drives an AC motor.

[Background of the invention]

PWM inverters are used to drive AC motors such as induction motors and synchronous motors. The firing of the 2wM inverter is controlled by a pulse width modulated pulse obtained by comparing the modulated wave and the carrier wave.

When driving an AC motor with a PWM inverter, the modulated wave is a voltage command signal (sine wave signal) whose amplitude changes according to the deviation between the current command signal and the PWM inverter's current detection signal. The current command signal is obtained as a sine wave signal whose amplitude changes in proportion to the deviation between the speed command signal and the speed detection signal of the AC motor.

By the way, when an AC motor is driven by a PWM inverter, magnetic sound (noise) is generated from the motor.

The reason why magnetic noise is generated is that the inverter's output current contains high-frequency components. The noise becomes louder when the response of the speed control system of the AC motor is increased, especially for electric RJJ motors.
It causes discomfort when the level of mechanical noise is low, such as when the machine is operating at low speed.

On the other hand, AC electric motors are being installed not only in high-noise areas but also in low-noise areas. Noise that gives a sense of pleasure is not good for the working environment either. Therefore, it is desired to reduce the noise generated by an AC motor driven by a PWM inverter.

Conventionally, as a method for reducing noise when driving a four-layer excited motor with a PWM inverter, a method has been proposed in which the primary #Lρ excitation force is reduced when the load becomes light, and the motor magnetic flux is changed. ing. However, although this method reduces noise when there is no load or under load, it has the disadvantage that noise cannot be reduced when the load is on because the magnetic flux reaches the rated value.

[Purpose of the invention]

The present invention has been made in response to the above-mentioned problems, and its purpose is to provide a PWM inverter control method that can reduce noise regardless of the load state and perform speed control with high response. .

[Summary of the invention]

The feature of the present invention is that the ripple of the sine wave voltage command signal (modulated wave) obtained according to the deviation between the current command signal and the current detection signal that detects the output current of the PWM inverter increases the rotational speed of the AC motor. The reason is that it is suppressed so that it becomes smaller as it decreases.

Other features of the invention will become apparent from the description below.

[Embodiments of the invention]

FIG. 1 shows an embodiment of the present invention.

In FIG. 1, an AC motor 2 is driven by a PWM inverter l. The output current of the PWM inverter is detected by a current detector 14. A speed detector 3 is mechanically directly connected to the AC motor 2. The speed command signal N* of the speed phasing circuit 11 and the speed detection signal N of the speed detector 3 are applied to the speed control circuit 12 with the polarities shown. The speed control circuit 12 outputs a current control signal (DC signal) 9 that commands the magnitude of the input terminal of the motor 2 in proportion to the speed deviation ΔN. Current control signal 11 is guided to current command circuit 13 . The current command circuit 13 manually inputs the current control signal 1'', generates a current command signal (sine wave signal) 1* as described later, and applies it to the DC control circuit 15. [+i, current control circuit 1]
5 compares the current command signal 11 and the current detection signal l output from the Fli current ratio detector 14 with the polarity shown in the figure, and calculates the current deviation Δ
A sine wave positive pressure command No. 4g V* with an amplitude corresponding to i is output. The multiplier 19 multiplies the command signal v of tM1f and the gain setting of the gain setting circuit 18 by multiplying it by g*total loss, and outputs the compensation voltage command signal vc. The gain setting circuit 18 inputs the speed detection signal N and outputs a gain setting signal g* proportional to the rotational speed as shown in FIG. The pulse generating circuit 17 compares the compensation voltage command signal VC* (modulated wave) with the triangular wave signal (carrier wave) T of the emitter 16, and generates a pulse width modulated pulse (PWM) that turns on and off the switching element constituting the inverter 1. Pulse) all occur.

In addition, in FIG. 1, the current detector 14 and the current control circuit 1
5. The multiplier 19 and the pulse generation circuit 17 need to be provided according to the number of phases of the inverter 1, but only one phase is shown.

Next, the entire operation will be explained.

The current control signal ■* of the speed control circuit 12 commands the magnitude of the input terminal (effective current) i of the AC motor 2. The current command circuit 13 outputs an AC current command signal i* by the following calculation.

First, if AC 1@machine 2 is a synchronous motor, the stain flow command signal I* is determined by the following formula.

i”=I”sinωt ・・・・・・・・・
(1) 5 incc + t in the +11 formula is a sine wave phase reference signal, and as is well known, this sine wave phase reference signal is transmitted to a position detector (not shown) attached to the shaft end of the AC motor 2 or to the motor. It is obtained from the terminal voltage of 2.

When the father flow motor 2 is an induction motor and performs vector control, the current command signal i* is determined by the following equation.

i* = i, CO3ωt+Ib5inωt = I”
sin (ωt+θ) −・−・−+21 Here, it is.

In equation (2), Ia is the effective current of the speed control circuit 1
This corresponds to an output of 1 m for 2. Further, Ib corresponds to a reactive component (direct current and inductive DJJ magnetic current component), and generally 1 is a constant value. 'f, s1nωt, and cosωt are two-phase sinusoidal phase reference signals, which, as is well known, correspond to the magnetic flux phase of the entrancing mechanism.

The current command circuit 13 generates the current command signal i* as described above.
occurs.

The DC control circuit 15 receives a current command signal 1* and a current detection signal i.
A full voltage command signal V* with an amplitude proportional to the deviation Δ1 is outputted and added to the multiplier 19. The 11 multiplier 19 performs a function equivalent to a variable gain amplifier, and the gain is determined by the gain setting circuit 18. The gain setting circuit 18 has a characteristic of increasing the gain setting signal g in proportion to the rotational speed N, as shown in FIG. As a result, the gain of multiplier 19 increases as the speed of electric motor 2 increases.

In addition, when the multiplier 19 becomes saturated, the gain may be made constant in the high speed range as shown by the broken line in FIG. 2, which shows the characteristics of the gain setting circuit 18. Multiplier 19 multiplies voltage command signal V* and gain setting signal g* to output compensation voltage command signal vc*. Assuming that the amplitude of the voltage command signal V* is a constant value, the amplitude of the compensation voltage command signal yc1) increases as the rotational speed of the electric motor 2 increases. The compensation voltage command signal vc1 obtained from the multiplier 19 in this manner is input to the pulse generation circuit 17 as a modulated wave. The pulse generating circuit 17 compares the compensation voltage command signal vc with the carrier wave T of the oscillator 16, and generates a "1" level PWM pulse during the period of vc*>T. By controlling the switch yx+ of the inverter 1 on and off using this PWM pulse, the output current of the inverter 1 is controlled to follow the current command signal j. Such an operation is similarly performed for other phases with a phase difference of 120 degrees if the inverter 1 has three phases. As a result, the AC motor 2 is supplied with a current proportional to the speed side (current control signal 2 generated by the M1 circuit 12), and rotates at a speed that matches the speed command signal N*.

The PWM inverter is controlled as described above, and the curve deviation Δ between one current command signal and one current detection signal is
The curve at the compensation voltage command signal vc1po as seen from i is made to increase in proportion to the rotational speed of the AC motor 2. In other words, the current command circuit 13 and the current control circuit 15
, the multiplier 19, the pulse generation circuit 17, the inverter 1, the current detector 14, etc. 2.As the gain of the current control system increases, seven voltage command signals (compensation voltage command signal v c'1'
) becomes larger. This is because the amplitude of the ripple included in the current detection signal i increases as the gain increases.

The PWM pulse is obtained by comparing the voltage command signal V* and the carrier wave T, but if the ripple component is large, ripples are generated in addition to the P'WM pulse obtained by comparing the fundamental wave component of the voltage command signal V* and the carrier wave T. A PWfvf pulse is also generated by comparing the minute and carrier wave T.

The pWM inverter 1 not only performs the switching necessary to output the V fundamental waves of the voltage command signal, but also performs unnecessary switching due to ripples. This wasteful switching also causes harmonic current to flow through the AC electric machine 2, resulting in increased noise. In the present invention, the gain of the current control system is reduced during low-speed operation where noise is a problem, so the ripple included in the compensation voltage command signal vc* is reduced. When the ripple component becomes smaller, the number of unnecessary switching times due to the ripple component of the PWM inverter 1 can be reduced. Therefore, it is possible to reduce the amount of harmonics flowing through the AC motor 2 during low-speed operation, thereby reducing noise.

As described above, the present invention adjusts the cane of the current control system that controls the output current of the PWM inverter in proportion to the rotational speed of the AC motor, and includes it in the sinusoidal voltage command signal that is compared with the carrier wave during low-speed operation. Since the ripple generated by the P-VM inverter is reduced, unnecessary switching is not performed by the P-VM inverter, and noise can be reduced.

Note that the gain of the current control system is reduced during low-speed operation, but since the gain is changed approximately in proportion to the magnitude of the back electromotive force of the AC motor, the gain of the 1.4'l loop that makes the AC motor blue. There is almost no change in response, and there is no decrease in responsiveness.

Also, since the gain of AC I is increased during high-speed driving, the noise (electromagnetic sound) increases.

However, in 1st (5th) gear, the operating machine noise becomes louder, so magnetic noise becomes relatively less of a problem.

Here, in the embodiment of FIG. 1, the multiplier 19 is
It is provided inside the ll side 1 circuit 15, but between the upstream command circuit 13 and the current control circuit 15, and the current detector 14.
A multiplier is inserted between the current control circuit 15 and the current control circuit 15, so that the gain of the current command signal i* or the current detection signal 1 inputted to the current control circuit 15 as seen from the current command circuit 13 or the current detector 14 is determined as well as the rotation speed. The noise can be similarly reduced even if the noise is increased.

The current control circuit 15 is usually an operational amplifier, a human resistor,
It consists of feedback resistors, etc. Therefore, multiplier 19'
! Even if the value of the human resistance or feedback resistance of the current control circuit 15 is adjusted by the gain setting signal g* of the gain setting circuit 18 without providing il-, the noise can be similarly reduced.

As described above, the gain of the current control system that controls the output current of the PWM inverter of the present invention is changed in proportion to the rotational speed of the AC motor, and the ripple included in the sine wave voltage command signal is reduced during low-speed operation. This is to reduce noise.

FIGS. 3 to 5 show experimental results for the embodiment shown in FIG. 1.

Figure 3 shows tq at constant speed, which was actually measured by the inventors.
FIG. 3 is a characteristic diagram showing the relationship between current control system gain and noise. As is clear from FIG. 3, the smaller the gain of the current control system, the lower the noise level.

Figure 4 shows the followability of the rotational speed and current when the gain of the current control system is constant (if the followability is good, the difference in magnitude and phase between the current command signal 1* and the current detection signal i will be small) FIG.

Custom made a in FIG. 4 is for a case where the gain is large, and the characteristic is for a case where the gain is small. From FIG. 4, it can be seen that in order to improve the followability of the current required to bring the AC motor to the required speed, the gain of the current control system should be increased as the rotational speed increases.

As is clear from the results of the disasters shown in Figures 3 and 4, noise can be reduced by reducing the gain of the current control system during low speed rotation as in the present invention.1. And the current is proportional to the rotation speed: 1
By increasing the gain of the jlJ44 system, speed control can be performed with high response.

Figure 5 shows the measured characteristics of rotational speed and noise.

The % characteristic a shown by the broken line in Fig. 5 is the characteristic when the gain of the current control system is constant regardless of the rotation speed.In the present invention, where the gain is changed in proportion to the rotation speed, the characteristic shown by the solid line is the characteristic. . As is clear from this characteristic, according to the present invention, the overall noise level is reduced over the entire speed range, and it can be seen that the noise level can be significantly reduced especially during low speed rotation.

FIG. 6 shows another embodiment of the invention.

In FIG. 6, the gain of the current control system is changed by changing the amplitude value of the carrier wave T.

In FIG. 6, the same symbols as in FIG. 1 indicate equivalents. 20 is a gain setting circuit that outputs a gain setting signal gt for setting the gain of the current control system according to the rotational speed N as shown in FIG. 'Jffl This is a multiplier for changing according to the signal gτ.

The operation shown in FIG. 6 will be explained.

The gain setting circuit 20 outputs a gain setting signal gr that decreases as the rotational speed N increases, as shown in FIG.

The carrier wave T and the gain setting signal gr are calculated by the calculator 21 and input to the comparator 17.The width of the carrier wave T input to the comparator 17, that is, the amplitude value of the triangular wave is As the speed increases, it becomes much smaller. If the amplitude value of the heavy pressure command signal V* of the current control circuit 15 is 7 lines, and the carrier wave T (triangular wave is A) which is the cutting signal of the multiplier 21, the output force from the PWM inverter 1, the magnitude of the pressure V is Equation (4) becomes as follows, and V
■ -... (4) 11 (relative to the amplitude value V zero of the pressure command signal V', ν11 is inversely proportional to the 12i 11Q+? value A of the carrier wave III. Therefore, When the amplitude value of the carrier wave T input to the comparator 17 is reduced by I/L due to the increase in speed, the amplitude value v1 of the voltage command signal V* is obtained.
The gain of the heavy pressure V as seen from the PWM inverter l
The gain of increases. Its, Kinka, current fljlJ 1
The gain of the wholesale yarn increases as the rotational speed N increases. In the embodiment shown in FIG. 6 as well, the speed control can be performed with high response as in FIG. 1 and 10j, and the noise η during low speed rotation can be reduced. Note that the characteristics of the gain setting circuit 20 shown in FIG. 7 may be made constant in the low speed range as shown by the broken line in FIG. 7 when the multiplier 21 is saturated in the low speed range.

Next, in the embodiment shown in FIG. 6, the multiplier 21 is provided to change the width of the carrier wave 'r, but it is also possible to change it directly with the oscillator.

FIG. 8 shows an example of an oscillator 16A used in that case.

In FIG. 8, 101 to 105 are operational amplifiers, Rl=
R14 is a resistor, Dt + D2 is a diode, and C is a capacitor. The operational amplifiers 101, 104 and 105 perform operations to invert the sign of the human input signal, and the operational amplifier 1
0'2 constitutes an integrator. Further, the operational amplifier 103 constitutes a comparator with hysteresis characteristics that can change the hysteresis width with respect to human power according to the outputs of the operational amplifiers 104 and 105.

The operation shown in FIG. 8 will be briefly explained using FIG. 9.

The operational amplifier 102 performs an integral operation and generates a triangular wave as shown in FIG. 9(a). The operational amplifier l03 operates as a hysteresis comparator and outputs a square wave signal as shown in FIG. 9(b).

The sign of the square wave A100 (b) is inverted by the operational amplifier 101,
When the operational amplifier 102 is powered manually, the operational amplifier 102 outputs a triangular wave. The amplitude value of the triangular wave is calculated by operational amplifier 1.
This is done by changing the hysteresis width in 03. The hysteresis width is determined by the operational amplifier 104. This can be realized by changing the output limiter value of the operational amplifier 103 depending on the ios. In FIG. 9, the solid line shows the waveform when the hysteresis width is set narrow, and the dashed-dotted line shows the waveform when the hysteresis width is set wide. The hysteresis IM can be changed 4M times by the gain setting signal gt of the cane setting circuit 20, and as a result, the amplitude value of the carrier wave T can be changed continuously.

As shown in FIG. 8, the oscillator 16 itself can change the amplitude value of the carrier wave according to the speed.

As shown in Figures 6 and 8, even if the amplitude value of the plate wave transmission is changed according to the rotation speed, the gain of the current 1171J control system remains constant.P1 Speed control with high response and low noise over a wide speed range. I can do it. Furthermore, when the AC motor 2 is a three-phase machine, three sets of the current control circuit 15 and the comparator 17 are required for each phase, but according to the embodiment of FIG. 6, the oscillator 16 and the multiplier 21 are Since only one component is required for each phase, there is an advantage that fewer components are required compared to the embodiment shown in FIG.

FIG. 10 shows another embodiment of the present invention.

In FIG. 10, the same symbols as in FIG. 1 indicate equivalents. 23 is a transformer for insulatingly detecting the output voltage of the PWM inverter 1; 24 is a voltage detection circuit consisting of a filter that converts the line voltage detected by the transformer 23 into a phase voltage and further removes ripple; and 25 is a voltage detection circuit It is an adder.

In FIG. 10, the voltage detection circuit 24 detects a phase voltage corresponding to the induced voltage of the AC motor 2, ignoring the leakage impedance drop. If the excitation current of the AC motor 2 is constant, the induced voltage changes in magnitude in proportion to the rotation speed. Therefore, if the voltage detection signal V of the voltage detection circuit 24 and the voltage command signal v of the current control circuit 15 are added by the adder 25 to obtain a compensation voltage command signal Vc'', then the current command signal 1
The gain from the deviation Δi between the current detection signal 1 and the compensation voltage command signal VC increases as the rotational speed increases.

In this manner, also in the embodiment shown in FIG. 10, the gain of the current control system can be changed in proportion to the rotational speed.

In the embodiment shown in FIG. 10, the phase voltage corresponding to the induced voltage is detected by detecting the actual voltage, but the signal corresponding to the phase voltage can also be obtained in the following manner. That is, when the AC motor 2 is an induction motor and the torque current component and excitation current component of the primary current are controlled independently, the current command circuit 13 is configured to multiply the torque current phase reference signal by the rotation speed N by 1. It is easily detectable.

FIG. 11 shows another embodiment of the present invention.

11 is different from FIG. 1 in that a first-order lag circuit 31 is provided in place of the multiplier 19, and the time constant of the first-order lag circuit 31 is set by a time constant setting circuit 32. As shown in FIG.
Reduce the time constant of 1.

When the time constant of the first-order delay circuit 31 is varied in inverse proportion to the rotation speed N as shown in FIG. 12, the ripple of the compensation voltage command signal vc9 becomes small in the low speed range.

The ripple of the compensation voltage command signal vc" increases as the rotational speed N increases. Since the cutoff frequency of the first-order lag circuit 31 increases in proportion to the rotational speed N, the frequency characteristics of the current control system closed loop also change with the rotational speed. It increases as N increases.On the other hand, when the gain of the current control system is increased, the frequency characteristics also increase.Therefore, if the time constant of the first-order lag circuit 310 is changed according to the total rotation speed, the gain of the current control system will increase isometrically. will change.

As described above, in the embodiment shown in FIG. 11, noise at low speeds can be reduced and speed control can be performed with high response, as in the embodiment shown in FIG.

Note that the first-order delay circuit 31 may be incorporated into the current control circuit 15, or may be inserted into the feedback circuit for the current detection signal i to obtain the ringing.

FIG. 13 shows another embodiment of the present invention.

FIG. 13 shows a current control circuit in which the current control circuit Iri is changed in proportion to the rotational speed to avoid unnecessary switching due to ripples.

FIG. 13 shows an example of the current control circuit 15A.

2 in FIG. 13, 106, 107 are operational amplifiers, 10
8 is a limiter setting circuit that outputs a limiter setting signal V/' as shown in FIG. 15 in response to the speed detection signal N of the speed detector 3, R1-Rtt are resistors, Dl and D2 are diodes, and C is a capacitor. .

This current control circuit 15A differs from the current control circuit 15 in that a limiter circuit is provided to prevent the output signal (voltage command signal v*) of the operational amplifier 106 from exceeding the positive and negative fixed values of Wr.

The operational amplifier 106 receives a current command signal 1 and a current detection signal.
WJ is used as a deviation amplifier to amplify the deviation Δ star of
4 and a series circuit of a capacitor are connected. The current control circuit 15A performs proportional-integral operation.

The output of operational amplifier 106 becomes voltage command signal V*. On the other hand, the limiter setting circuit 108 limits the output signal of the operational amplifier 106. For limit setting, set the limiter setting signal of limiter setting device 10B to Vt, and resistor fLs
and R7, R6 and Rs, Rto and 6. If the values of R11 are chosen equally, it is ±17V! It is determined by

Therefore, by arbitrarily selecting the value of one limiter setting signal V, the maximum value (absolutely 1 frequency) of the voltage command signal V* can be freely changed.

First, let us explain what it means to apply a limiter to the voltage command signal V''.
This will be explained with reference to FIG.

FIG. 14 is a waveform diagram showing how the PWM pulse applied to the PWM pulse 1 differs depending on the presence or absence of a limiter.

FIG. 14(a) shows the relationship between the carrier wave T and seven voltage command signals when there is no limiter, and FIG. 14(b) shows the PWM pulse obtained from the comparator 17 at this time.

Note that a waveform V indicated by a dotted line in FIG. 2(a) indicates a fundamental wave of voltage. Also, Fig. 14 (C) shows the waveform when there is a limiter, and Fig. 14 (d) shows the PWM pulse at this time.
No-0 Now, the PWM pulses shown in FIGS. 14(b) and 14(d) are related to the output voltage (effective value) of the PWM inverter 1.

When the output of the operational amplifier 106 is limited by the limit value ■l* shown by the dashed line in FIG. 14(C), the ripple included in the seven voltage command signals is reduced. For this reason, the PWM pulse becomes as shown in FIG. 3D, and compared to FIG. When the number of switching operations is reduced, the harmonic component included in the output voltage of the inverter 1 can be reduced, and noise can be reduced.

As the speed of the AC motor 2 increases, the basic voltage distribution V of the PVJbi inverter 1 shown by the dotted line in FIG. 14(a) increases in proportion to the speed, so the limiter value vl* is changed in accordance with the speed. .

FIG. 15 shows an example characteristic diagram of the limiter setting circuit 108.

As shown in FIG. 15, as the speed N increases, the limiter value VN increases t, and the limiter value v11 is set so that it is slightly larger than the amplitude value A of the triangular wave T.

Note that the characteristics shown in Fig. 15 are based on the magnitude A of the carrier wave (triangular wave) T.
Although we have shown a case where the value is constant, the same concept can be applied even if the value is changed.

In this way, by applying a limiter to the voltage command signal v in the current control circuit 15A, the number of times the inverter 1 is switched is reduced when the induced voltage is small and the ripple component is large.

If the number of times of switching is small, the output voltage (effective value including harmonics) of the PWM inverter 1 does not decrease, but the gain of the current control system is apparently changed.

As a result, in the embodiment shown in FIG. 13 as well, noise can be reduced in the low speed range and speed control can be performed with high response.

Note that if the current control circuit 15A shown in FIG. 13 is used as the current control circuit 15 in each of the embodiments shown in FIGS. 1, 6, and 1θ, it is possible to further reduce noise.

〔Effect of the invention〕

As explained above, according to the present invention, noise can be reduced in a wide speed range regardless of the load condition by changing the gain of the current control system in proportion to the rotational speed of the AC motor.
It also enables high-response speed control.

In the above-described embodiment, the gain of the current control system is changed depending on the rotational speed, but it is obvious that the gain may be changed depending on the driving frequency of the AC 1b and the moving rock.

Further, although the above-described embodiment shows an analog circuit, the present invention can of course be applied to digital control using a microprocessor or the like.

Furthermore, in the above embodiment, g4t4. When applied to motive, the explanation was given to all centers, but it goes without saying that it can also be applied to Shikiden @ machine.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
Figures 3 to 5 are characteristic diagrams of the gain setting circuit shown in the figure, Figures 3 to 5 are experimental characteristic diagrams for which detailed explanation of the present invention is unnecessary, Figure 6 is a configuration diagram showing another embodiment of the present invention, and Figure 7 is a diagram showing the characteristics of the gain setting circuit. 8 is a configuration diagram showing an example of the oscillator shown in FIG. 6, FIG. 9 is an operating waveform diagram of FIG. 8, and FIG.
0.11 is a block diagram showing other embodiments of the present invention, FIG. 12 is a characteristic diagram of the time constant setting circuit in FIG. 11, and FIG. 13 is a block diagram showing an example of the current control circuit according to the present invention. , FIG. 14 is an operating waveform diagram of the current control circuit in FIG. 13, and FIG. 15 is a characteristic diagram of the limiter setting circuit in FIG. 13. 1... PWM inverter, 2... AC motor, 13
...Current command circuit, 14...! Current detector, 15...
・Current control circuit, 16... Oscillator, 17... Comparator, 18° 1st function YzI2] Fig. 3 Fig. 4
Figure 5: Roseo Cliff N=Kuchisaku Detour N→No. 6
figure/? Rotating arm N = No. 8 (211 Yq sword rod 70 Figure brown) Figure 12 70 Speed rolling seat N- 钒 () 3 Figure rod No. 5 Figure mouth rolling speed deer N- Figure 14 (d)

Claims (1)

[Claims] 1. It drives an AC motor, and is controlled by a pulse width modulated pulse obtained by using a voltage command signal obtained according to the deviation between a current command signal and a current detection signal as a modulating wave, and comparing this modulated wave with a carrier wave. A control method for a PWM inverter, which is characterized in that the ripple of the low voltage command signal is suppressed to become smaller as the rotational speed of the AC motor becomes lower. 2. In item 1 of ``Percent Allowable Removal Range I11'', suppression of the ripple of the sine wave voltage command signal is achieved by adjusting the gain for determining the sine wave voltage command number 16 from the deviation between the current command signal and the current detection signal. P is characterized by
WM inverter control method 1.3. Claim 2
In the PW, the gain is adjusted by adjusting the Id current command signal or the current detection signal.
M inverter control method. 4. The method of controlling a PWM inverter according to claim 1, wherein the gain adjustment is performed by changing the amplitude value of the carrier wave in inverse proportion to the rotational speed of the AC electric machine. 5. Claim 1 provides that the gain adjustment is performed by changing a limiter value for obtaining the voltage command signal from the deviation between the current command signal and the current detection signal in proportion to the rotational speed of the AC motor. Characteristic PWM inverter control method. 6. A PWM inverter that drives an AC motor, and a PWM inverter that drives an AC motor;
A current gain circuit that outputs a voltage command signal according to the deviation between the current command signal and the current detection signal of the M inverter; (to) a comparison means for outputting a pulse width modulated pulse, and a phosphor control device for reducing ripples in the voltage command signal as the rotational speed of the AC motor decreases. 7. 7. The PWM inverter control device according to claim 6, wherein the ripple suppression means is performed by adjusting the gain of the current control circuit. 8. The PWM inverter according to claim 7, wherein the gain of the current control circuit is adjusted by changing the amplitude value of the current command signal or the current detection signal in proportion to the rotational speed of the AC motor. control device. 9. Claim 6 is characterized in that the ripple suppressing means changes the amplitude value of the carrier wave in inverse proportion to the rotational speed of the AC motor.
WM inverter control device. 10. In claim 6 of the watch, the ripple suppressing means is a first-order lag circuit that smoothes the tli pressure command signal or the current detection signal, and whose time constant is adjusted in inverse proportion to the rotational speed of the AC motor. A control device for a PWM inverter, characterized in that: 11. In claim 6, the ripple suppressing means sets a limiter value of the current control circuit to the AC'i.
'! j@! A control device for a PWM inverter, characterized in that the control device changes the rotation speed of one device in proportion to the rotation speed.