JPH05268772A - Inverter control method and inverter control device - Google Patents

Abstract

(57) [Summary] [Purpose] Compensate for output voltage fluctuations. It suppresses the imbalance of the three-phase AC output due to the fluctuation of the output voltage. [Structure] The voltage value of each phase output from the inverter is detected by the voltage detectors 7a to 7c, and the detected voltage value is fed back to the current control arithmetic unit 3 side as a voltage feedback value to obtain the voltage command value and the voltage feedback. The voltage value of each phase output from the inverter is controlled so as to follow the voltage command value based on the value and. [Effect] The fluctuation of the output voltage when the output of the inverter is low can be compensated with high accuracy. Further, it is possible to suppress the imbalance of the balance of the three-phase AC output due to the fluctuation of the output voltage, and to perform stable control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter control method and an inverter control apparatus, and more particularly to an inverter control method and an inverter control apparatus capable of controlling an output voltage value with high accuracy.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of an inverter control device 51 including a conventional inverter. The inverter control device 51 controls the rotation of the three-phase AC electric motor 57 by outputting the three-phase AC power from the power amplifier 55. In this inverter control device 51, the current command calculator 52 calculates the current command value i for each phase of U, V, and W from the supplied current command.
u, iv, iw are calculated, and subtracters 53a, 53 are respectively provided.
b, 53c. The subtractor 53a, based on the U-phase current command value iu and the output current feedback value IFu supplied from the current command calculation unit 52, the U-phase current deviation Δiu.
Is output to the current control calculation unit 54. Also, the subtractor 5
3b obtains a V-phase current deviation Δiv based on the V-phase current command value iv and the output current feedback value IFv supplied from the current command calculation unit 52, and outputs the V-phase current deviation Δiv to the current control calculation unit 54. Further, the subtractor 53c calculates the W-phase current deviation Δiw based on the W-phase current command value iw and the output current feedback value IFw supplied from the current command calculation unit 52, and outputs it to the current control calculation unit 54.

The current control calculation unit 54 includes subtractors 53a and 5a.
The current deviations Δiu, Δiv, and Δiw of the U, V, and W phases supplied from 3b and 53c are respectively referred to as voltage command values vu and v.
It is converted into v and vw and output to the power amplification unit 55.

The power amplifier 55 includes an inverter composed of a bridge circuit composed of switching elements, and the voltage command value v supplied from the current control calculator 54.
The switching elements of the bridge circuit are turned on / off based on u, vv, vw, and three-phase AC power is supplied to the three-phase AC motor 5.
Supply to 7.

FIG. 3 is an electric circuit diagram showing the structure of each phase of the power amplifier 55, which is composed of a PWM generator 55a, a dead time generator 55b, an inverter 55c and the like.

Returning to FIG. 2, the U-phase current detector 56a detects the U-phase current Iu output from the power amplifier 55 and outputs the output current feedback value IFu to the subtractor 53a. Further, the V-phase current detector 56b includes a power amplifier 55
The V-phase current Iv output from the
The output current feedback value IFv is output to b. The W-phase current detector 56c detects the W-phase current Iw output from the power amplifier 55 and outputs the output current feedback value IFw to the subtractor 53c.

In this inverter control device 51 for a three-phase AC motor, the U-phase current detector 5 detects the phase currents of the U, V and W phases.
6a, V-phase current detector 56b, and W-phase current detector 56c, and subtractor 53 outputs the output current feedback values IFu, IFv, IFw corresponding to the detected phase current of each phase.
a, 53b, 53c, and the current command values iu, iv, iw of each phase and the output current feedback values IFu, IFv, IFw are used to determine the current value of each phase supplied to the three-phase AC motor 57. The current command value i
The inverter of the power amplification unit 55 is controlled so as to match u, iv, and iw.

[0008]

In the above-mentioned conventional inverter control device 51, the inverter 5 of the power amplification section 55 is provided.
5c is composed of a bridge circuit composed of switching elements. The dead time period is set in the control signal supplied to the switching elements so that a pair of upper and lower switching elements forming one side of the bridge circuit do not turn on at the same time. (A period in which a pair of upper and lower switching elements are simultaneously turned off) is provided. During this dead time period, the output voltage waveform of the power amplifier 55 is distorted. Factors that give distortion to the output voltage waveform include variations in the characteristics of the switching element in addition to the dead time period.

Distortion of the output voltage waveform causes pulsation of torque of the AC motor and uneven rotation when the AC motor is driven. In particular, when the AC motor is operated at low voltage and low speed, the influence is great and becomes a problem.

For example, there is a problem in controlling the AC motor for maintaining the pressure of the injection molding machine (the rotation speed of the AC motor for maintaining the pressure of the injection molding machine is 1 rpm or less and the torque pulsation is 1% or less. There is a need).

An inverter control technique for compensating for torque pulsation and uneven rotation in such an AC motor is disclosed, for example, in Japanese Examined Patent Publication No. 59-8152.
There is a disclosure proposal in Japanese Patent Laid-Open No. 123478.

FIG. 4 shows a voltage type inverter control method disclosed in Japanese Patent Publication No. 59-8152. In this voltage type inverter method, the output current direction for each phase is detected, the compensation amount is calculated according to the output current direction and the size of the dead time period, and the compensation amount is fed back to the switching time of the switching element. It is a thing.

FIG. 5 shows a voltage type inverter control method disclosed in Japanese Patent Laid-Open No. 59-123478. This voltage-type inverter control method detects the magnitude and direction of the output current for each phase, calculates the compensation amount according to the magnitude and direction of the output current, and the magnitudes of the motor winding resistance and wiring resistance, and The quantity is fed back to the switching time of the switching element.

However, in the techniques disclosed in Japanese Patent Publication No. 59-8152 and Japanese Patent Publication No. 59-123478, variations in the turn-off characteristics of a pair of upper and lower switching elements forming one side of the bridge circuit of the inverter and the switching elements are eliminated. The fluctuation of the output voltage due to the fluctuation of the turn-off time due to the magnitude of the flowing current or the temperature change is not compensated, and the unbalance of the three-phase AC output due to the fluctuation is not compensated. In other words, in these technologies, the output voltage fluctuates due to variations in the turn-off characteristics of the pair of upper and lower switching elements that form one side of the bridge circuit of the inverter, and variations in the turn-off time caused by the magnitude of the current flowing through the switching elements or temperature changes. Occurs or a voltage imbalance occurs in the three-phase AC output, there is a problem that pulsation occurs in the torque generated by the AC motor.

Therefore, an object of the present invention is to provide an inverter control method and an inverter control device capable of compensating for fluctuations in the output voltage and suppressing the unbalance of the three-phase AC output due to fluctuations in the output voltage. is there.

[0016]

According to a first aspect of the present invention, the present invention provides an inverter control method for detecting a current value of each phase output of an inverter and feeding back the current value by a current feedback loop. Provided is an inverter control method characterized by detecting and feeding back a voltage value of each phase output.

According to a second aspect, the present invention provides an output current value detecting means for detecting an output current value, and a voltage command value based on the output current value and the current command value detected by the output current value detecting means. Current control calculation means for generating, output voltage value detecting means for detecting output voltage value, voltage for generating an inverter voltage command value based on the output voltage value detected by the output voltage value detecting means and the voltage command value Control calculation means,
An inverter control device comprising: a power amplifier that supplies power to a load based on the inverter voltage command value.

[0018]

In the inverter control method of the present invention, the current value and voltage value of each phase output from the inverter are detected,
The detected output current value and output voltage value of each phase are fed back to the input side respectively, and the current value and voltage value of each phase output from the inverter are controlled so as to follow the current command value and the voltage command value, and output. Compensates for voltage fluctuations,
It suppresses the imbalance of the three-phase AC output due to the fluctuation of the output voltage.

Further, in the inverter control device of the present invention, the voltage value of each phase output from the inverter is detected by the output voltage value detecting means, and the detected voltage value is fed back to the input side to obtain the voltage command value and the feedback. The voltage value of each phase output from the inverter is controlled so as to follow the voltage command value based on the obtained voltage value.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in the drawings. However, this does not limit the present invention. FIG. 1 is a configuration diagram of an inverter control device 100 including an inverter according to an embodiment of the present invention. The inverter control device 100 includes a current command calculation unit 1, subtractors 2a to 2c, a current control calculation unit 3, and subtractors 4a to 4c.
c, a voltage control calculation unit 5, voltage detectors 7a to 7c that detect the output voltage of the power amplification unit 6, and current detectors 8a to 8c that detect the output current of the power amplification unit 6. The rotation of the three-phase AC motor 9 is controlled by controlling the power amplification unit 6.

The current command calculator 1 calculates the current command values iu, iv, iw for each phase of U, V, W from the supplied current command and outputs them to the subtractors 2a, 2b, 2c, respectively. On the other hand, the current detector 8 a outputs the U output from the power amplification unit 6.
Phase current Iu is detected and output current feedback value IFu
Is output to the subtractor 2a. Further, the current detector 8b is
The V-phase current Iv output from the power amplification unit 6 is detected and the output current feedback value IFv is output to the subtractor 2b. Further, the current detector 8c detects the W-phase current Iw output from the power amplification unit 6 and outputs the output current feedback value IFw to the subtractor 2c.

The subtractor 2a obtains a current deviation Δiu based on the U-phase current command value iu supplied from the current command calculation unit 1 and the output current feedback value IFu, and outputs it to the current control calculation unit 3. Further, the subtractor 2b is used in the current command calculation unit 1
The current deviation Δiv is obtained based on the V-phase current command value iv and the output current feedback value IFv supplied from the current control value and is output to the current control calculation unit 3. Further, the subtractor 2c uses the current command value iw of the W phase supplied from the current command calculator 1 and the output current feedback value IFw to determine the current deviation Δiw.
Is calculated and output to the current control calculation unit 3.

The current control calculation unit 3 performs a proportional-plus-integral operation, and U, supplied from the subtracters 2a, 2b and 2c,
The current deviations Δiu, Δiv, Δiw of the V and W phases are converted into voltage command values vu, vv, vw, respectively, and the subtracters 4a,
It outputs to 4b and 4c.

On the other hand, the voltage detector 7a detects the U-phase voltage Vu output from the power amplifier 6 and outputs the voltage feedback value VFu to the subtractor 4a. This voltage detector 7
A has a wide range of highly accurate voltage detection, and can detect a low output voltage with high accuracy. Further, the voltage detector 7b is
The V-phase voltage Vv output from the power amplification unit 6 is detected, and the voltage feedback value VFv is output to the subtractor 4b. This voltage detector 7b has a wide range of highly accurate voltage detection, and can detect a low output voltage with high accuracy. In addition, the voltage detector 7c detects the W-phase voltage Vw output from the power amplification unit 6 and subtracts the output voltage feedback value VFw from the subtractor 4c.
Is output to. The voltage detector 7c has a wide range of highly accurate voltage detection, and can detect a low output voltage with high accuracy.

The subtractor 4a uses the U-phase voltage command value vu and the output voltage feedback value VFu to determine the voltage deviation Δvu.
Is calculated and output to the voltage control calculation unit 5. The subtractor 4b is
V phase voltage command value vv and output voltage feedback value VF
The voltage deviation Δvv is calculated based on v and output to the voltage control calculation unit 5. The subtractor 4c calculates the voltage deviation Δvw based on the W-phase voltage command value vw and the output voltage feedback value VFw, and outputs it to the voltage control calculation unit 5.

The voltage control calculation unit 5 performs a proportional integration operation, generates inverter voltage commands viu, viv, viw according to the voltage deviations Δvu, Δvv, Δvw and outputs them to the power amplification unit 6.

The power amplifier 6 is composed of a PWM generator, a dead time generator, an inverter, etc., and is the same as that shown in FIG. In the power amplification unit 6, the switching element forming the inverter has the inverter voltage command vi.
The voltage command value vu, controlled by u, viv, and viw,
A voltage proportional to vv, vw is output to the three-phase AC motor 9. In the above embodiment, the current control calculation unit 3 and the voltage control calculation unit 5 perform the proportional-plus-integral operation, but they may perform the proportional operation and other control operations. Further, although it is desirable to control the current control calculation unit 3 and the voltage control calculation unit 5 by software processing, they may be controlled by hardware processing.

Inverter controller 10 according to the above embodiment
According to 0, the output current value feedback loop and the output voltage value feedback loop feed back the output current value and the output voltage value of the power amplification unit 6, respectively, and the current and the voltage supplied to the three-phase AC motor 9 are controlled. Therefore, it is possible to accurately compensate for fluctuations in the output voltage during low-speed rotation of the three-phase AC motor 9, suppress the loss of balance of the three-phase AC output due to fluctuations in the output voltage, and perform stable control. Can be done.

[0029]

According to the inverter control method and the inverter control device of the present invention, the output voltage of the inverter is fed back to compensate the fluctuation of the output voltage. Therefore, especially when the output voltage of the inverter is low, The fluctuation can be compensated with high accuracy. Further, it is possible to suppress the imbalance of the balance of the three-phase AC output due to the fluctuation of the output voltage, and to perform stable control.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an inverter control device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional inverter control device.

FIG. 3 is an electric circuit diagram showing a configuration of one phase of a power amplification unit.

FIG. 4 is an explanatory diagram of a conventional voltage type inverter control method.

FIG. 5 is an explanatory diagram of a conventional voltage type inverter control method.

[Explanation of symbols]

 100 Inverter control device 1 Current command calculation unit 2a Subtractor 2b Subtractor 2c Subtractor 3 Current control calculation unit 4a Subtractor 4b Subtractor 4c Subtractor 5 Voltage control calculation unit 6 Power amplification unit 7a Voltage detector 7b Voltage detector 7c Voltage detector 8a Current detector 8b Current detector 8c Current detector

Claims (2)

[Claims] 1. An inverter control method in which a current value of each phase output of an inverter is detected and fed back by a current feedback loop, a voltage feedback loop is added, and a voltage value of each phase output of the inverter is detected and fed back. Inverter control method. 2. An output current value detecting means for detecting an output current value, and a current control calculating means for generating a voltage command value based on the output current value and the current command value detected by the output current value detecting means. Output voltage value detecting means for detecting an output voltage value; voltage control calculating means for generating an inverter voltage command value based on the output voltage value detected by the output voltage value detecting means and the voltage command value; and the inverter voltage. An inverter control device comprising: a power amplifier that supplies power to a load based on a command value.