JPS5815492A - Control of pulse width control transducer - Google Patents

Abstract

PURPOSE:To prevent generation of a direct current component and an unbalance component in a motor current of pulse duration control transducer by a method wherein an integrator to integrate a deviation between a current command pattern signal and a current detection signal is provided in the preceding stage of a comparator. CONSTITUTION:The current command pattern signal sent from an arithmetic circuit 9 and the current detection signal sent from a current detector 10 are applied to input terminals of the integrator 11 and the comparator 12. The comparator 12 compares both the signals, and controls as to make the P side of GTO thyristors or diodes or the N side thereof to turn ON. At operation mentioned above, the deviation within the perscribed value is existing in the motor current, but because an output signal of the integrator 11 is applied to the comparator 12 in addition, the value of current command is made to vary corresponding to integrated quantity of the deviation between both the signals, and as a result, the motor current is controlled as to make the deviation mentioned above to become to zero.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling a pulse width controlled (PWM controlled) converter.

Recently, self-extinguishing power semiconductor devices have been developed and are often used in PWM control inverters for driving electric motors.

In a PWM control inverter, its output voltage is controlled by pulse width, and in this case, means for generating a pulse width control signal for controlling turn-on and turn-off of the semiconductor elements described above is required. There are several methods for this, but the simplest method is to add the motor current command pattern signal and current detection signal to a comparator with hysteresis and obtain a pulse width control signal as its output.

However, in this method, since the motor current is controlled within a predetermined deviation from the command value (the maximum deviation value is set by the hysteresis width of the comparator), errors within that deviation cannot be avoided. As a result, a direct current component and an unbalanced component occur in the motor current, causing problems such as torque ripple in the motor.

SUMMARY OF THE INVENTION In order to prevent the above-mentioned problems, it is an object of the present invention to provide a control method for controlling a motor current so that a direct current component and an unbalanced component do not occur.

A feature of the present invention is that an integrator for integrating the deviation is provided before the comparator to eliminate the deviation of the actual current value from the current command value.

FIG. 1 shows a circuit configuration diagram of a PWM control inverter showing one embodiment of the present invention. 1 is a diode rectifier, 2 is a DC reactor, 3 is a smoothing capacitor, 4 is a PWM control inverter composed of GTO syrisk, etc., 5 is an induction motor, and 6 is a speed command that commands the rotation speed of the motor 5. 7 is a speed detector, 8 is a speed deviation amplifier for amplifying the deviation between the speed command and the speed detection signal, and 9 is a signal corresponding to the speed deviation from the intensifier 8 and based on the speed detection signal. 10 is a current detector for detecting the motor current; 11 is an integrator for integrating the deviation between the current command pattern signal and the current detection signal; 12 is an integrator for integrating the deviation between the current command pattern signal and the current detection signal; A comparator made of a hysteresis material that compares the sum of the current command pattern signal and the output signal of the integrator 11 with the current detection signal; 13 is a comparator that alternately turns on the P side and N side of the GTO thyristor according to the output signal of the comparator; This is a gate amplifier that outputs a gate signal to turn off the device. Circuits corresponding to 10 to 13 are also provided for the other V and W phases, but since they are similar, their explanations will be omitted.

Next, the operation of the above circuit will be explained. Since the operations of Nos. 1 to 3 and Nos. 6 to 9 are well known, detailed explanation will be omitted. The output current of the inverter 4 (illustrated 1) increases when the P-side G T O zyristor or diode conducts, and similarly decreases when the N-side conducts. Because such repetition is performed, the output current becomes a sinusoidal current superimposed with a triangular waveform current that repeatedly increases and decreases. A current command pattern signal from the arithmetic circuit 9 and a current detection signal from the current detector 10 are applied to inputs of an integrator 11 and a comparator 12. The comparator 12 compares both signals, and controls the P-side GTO thyristor or diode to turn on when the former is smaller than the latter by a predetermined value or more, and conversely, when the former is smaller than the latter by a predetermined value or more. When this happens, the N side is similarly controlled to turn on. In the above operation, there will be a deviation within a predetermined value in the motor current, but since the output signal of the integrator 11 is added to the comparator 12, the integral amount of the deviation between both signals When the current command value changes according to
The motor current is controlled so that the deviation becomes zero.

Therefore, according to the present invention, the motor current can be controlled faithfully to the current command, and generation of a DC component and an unbalanced component can be prevented.

In the embodiment described above, both of the signals and the output signal of the integrator 11 are added to the input of the comparator 12, but the same effect can be obtained by adding only the output signal of the integrator 11.

FIG. 2 shows a circuit diagram of a PWM control converter showing another embodiment of the present invention. 4 is PWM which converts alternating current to direct current
A control converter, 14 is an actuator connected between the AC power source and the converter, 15 is a smoothing capacitor for absorbing the pulsation of the output current of the converter 4, and 16 is a DC device that commands the DC output voltage of the converter. Voltage command circuit, 17 voltage detector, 1
8 is a voltage deviation amplifier for amplifying the deviation between the DC voltage command and the voltage detection signal, 19 is a transformer for detecting the voltage of the AC power supply (AC system), and 9 is for the voltage deviation from the amplifier 18. a corresponding signal and a voltage from the transformer 19 (5); an arithmetic circuit that generates a power supply current command pattern signal (sine wave signal) synchronized with the power supply voltage based on the detection signal; 10;
is a current detector for detecting the power supply current; 11 is an integrator that integrates the deviation between the current command pattern/signal and the current detection signal; 12 is the sum of the current command turn signal and the output signal of the integrator and current detection A comparator 13 made of a hysteresis material for comparing signals is a gate amplifier that outputs a gate signal to alternately turn on and off the P side and N side of the GTO thyristor in accordance with the output signal of the comparator 12.

Next, the operation of this circuit will be explained. The AC input current (illustrated 1) of the converter 4 increases when the N-side GTO circuit or diode conducts, and similarly decreases when the P-side conducts. Because such repetition is performed, the power supply current becomes a sine wave current with a triangular wave current superimposed on it. Current command pattern signal from arithmetic circuit 9 and current detector 10
A current detection signal from the integrator 11 and comparator 12 is applied to the inputs thereof. The comparator 12 compares both signals, and (6) when the former is larger than the latter by a predetermined value or more, N
The side GTO zyristor or diode is controlled to be turned on, and conversely, when the former is smaller than the latter by a predetermined value or more, the P side is similarly controlled to be turned on. In the above operation, there is often a deviation within a predetermined value in the power supply current, but in addition, the comparator 12
Since the output signal of the integrator 11 is added to , the current command value changes according to the integrated amount of the deviation between both signals, and as a result, the power supply current is adjusted such that the deviation becomes zero. controlled by.

Therefore, according to the present invention, the power supply current can be controlled faithfully to the current command, and the generation of DC components and unbalanced components can be prevented. Therefore, it is possible to prevent the transformer in the AC system from being affected by biased DC magnetization.

Note that similar effects can be obtained by adding only the output signal of the integrator 11 to the input of the comparator 12, as in the case of the embodiment described above.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of a PWM control inverter implementing the pulse width control converter control method of the present invention, and FIG. 2 is a circuit diagram of another PWM control inverter implementing the pulse width control converter control method of the present invention.
It is a circuit block diagram of an M control converter. 1... Diode rectifier, 2... DC reactor,
3... Smoothing capacitor, 4... PWM inverter,
-Induction motor, 6...Speed command circuit, 7...Speed detector, 8...Speed deviation amplifier, 9...Arithmetic circuit, 10...Current detector, 11...・Integrator, 12...
・Comparator, 13... Gate amplifier, 14... Reactor, 15... Smoothing capacitor, 16... DC voltage command circuit, 17... Voltage detector, 18... Voltage deviation amplifier , 19... Power supply voltage check (■

Claims (1)

[Claims] ■ In a device that controls a motor using a pulse width control inverter, the command pattern signal of the motor current, the detection signal, and the output signal of an integrating means that integrates the deviation of both signals are added to the comparison means of the hysteresis characteristic material, and the output signal is Configure the inverter according to