JPH05137348A - Voltage type inverter device - Google Patents

Abstract

PURPOSE:To make it possible to prevent an electric motor from generating uneven rotations due to the voltage pulsation by correcting the voltage instruction on the basis of the detecting signals detected by a voltage detecting circuit by use of a subtracter and a voltage controller. CONSTITUTION:A subtracter 12 outputs the deviation signal which is obtained by subtracting the detection signal of a voltage detecting signal 18 from the sinusoidal wave voltage instruction provided by a voltage instruction generating circuit 11. The deviation signal is operated by a voltage controller 13 for amplification. A pulse width modulation is provided for the amplified deviation signal by a PWM modulating circuit 14. A dead time generating circuit 15 provides a dead time for the pulse width modulated deviation signal in order to prevent the upper and lower arms of a power switching circuit 17 from being short circuited. The deviation signal for which the dead time is thus provided is inputted into a base driving circuit 16 to drive the power switching circuit 17. The power switching 17 supplies a driving voltage (output voltage) to an alternating current motor 19 and the voltage detecting circuit 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage source inverter device for driving an AC motor, and more particularly to a voltage source inverter device for driving an AC motor by a pulse width modulation voltage.

[0002]

2. Description of the Related Art A conventional voltage source inverter device is shown in FIG. The conventional inverter device has a U phase, V
It has a voltage controller 31 and a power switching circuit 32 respectively corresponding to the phase and the W phase. Voltage control unit 3
1 includes a voltage command generation circuit 33, a PWM modulation circuit 34, a dead time generation circuit 35, and a base drive circuit 36.

In the U-phase voltage controller, the voltage command generating circuit 33 generates a sine wave voltage command proportional to the drive voltage.
The sine wave voltage command is input to the PWM modulation circuit 34, pulse width modulated, and output as a PWM voltage command. The dead time generation circuit 35 sets a dead time in the PWM voltage command so as to prevent a short circuit between the upper and lower arms of the power switching circuit 32. The PWM voltage command provided with the dead time is input to the base drive circuit 36, and the base drive circuit 36 drives the power switching circuit 32. As a result, the power switching circuit 32 supplies the drive voltage (output voltage) based on the sine wave voltage command to the AC motor 37. The operations of the V phase and the W phase are the same except that the phases of the sine wave voltage command differ by 120 °.

In the power switching circuit 32 of the inverter device shown in FIG. 3, a transistor is used as a power switching element, but other elements such as FET,
The same is true even if an element such as an IGBT is used.

[0005]

However, in the conventional voltage type inverter device, the dead time for preventing the upper and lower arms of the power switching circuit from being short-circuited causes an error in the output voltage. Further, this voltage error changes depending on the direction in which the AC motor flows. For this reason, when the AC motor is driven by the conventional voltage source inverter device, the current flowing in the AC motor becomes small especially at low speed operation, the output of the motor decreases, and the current equivalently includes ripple components, so that the normal operation is achieved. There are problems such as not rotating.

It is an object of the present invention to provide a voltage source inverter device capable of correcting a change in output voltage due to dead time and obtaining a stable output voltage.

[0007]

According to the present invention, there is provided a voltage source inverter device for receiving an instruction from a voltage instruction generating circuit, generating an output voltage based on the instruction, and driving an AC motor. In a voltage source inverter device having a power switching circuit that generates the output voltage and a dead time generation circuit that generates a dead time to prevent a short circuit between upper and lower arms of the power switching circuit, a voltage that detects the output voltage. A voltage type inverter device comprising: a detection unit and a command correction unit that corrects the command based on a detection signal from the voltage detection unit.

[0008]

The output voltage of the inverter device is detected by the voltage output circuit, and the subtracter subtracts it from the voltage command output from the voltage command generation circuit. The obtained deviation signal is amplified and an output voltage is generated based on the deviation signal.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a U-phase voltage controller according to an embodiment of the present invention. Since the V-phase and W-phase voltage control units have the same configuration as the U-phase voltage control unit, the description thereof will be omitted.

As shown in FIG. 1, the voltage controller of this embodiment includes a voltage command generation circuit 11, a subtractor 12, and a voltage controller 1.
3, PWM modulation circuit 14, dead time generation circuit 15,
It has a base drive circuit 16, a power switching circuit 17, and a voltage detection circuit 18.

Next, the operation will be described. Voltage command generation circuit 1
The sine wave voltage command output from 1 is input to the subtractor 12. The subtractor 12 outputs a deviation signal obtained by subtracting the detection signal of the voltage detection circuit 18 from the sine wave voltage command. This deviation signal is input to the voltage controller 13 and amplified and calculated. The amplified deviation signal is pulse-width modulated by the PWM modulation circuit 14. The dead time generation circuit 15 provides a dead time to the deviation signal pulse-width modulated so as to prevent the upper and lower arms of the power switching circuit 17 from being short-circuited. The deviation signal provided with the dead time is input to the base drive circuit 16, and the base drive circuit 16 drives the power switching circuit 17. As a result, the power switching circuit 1
Reference numeral 7 supplies a drive voltage (output voltage) to the AC motor 19 and the voltage detection circuit 18. The voltage detection signal detected by the voltage detection circuit 18 is output to the subtractor 12.

As described above, according to the present embodiment, the subtractor 12 and the voltage controller 13 are used to correct the voltage command based on the detection signal detected by the voltage detection circuit 18, so that a stable output is obtained. It is possible to obtain a voltage, and it is possible to prevent a decrease in output due to insufficient voltage and uneven rotation of the electric motor due to voltage pulsation.

The voltage detection circuit 18 will now be described. As shown in FIG. 2, the voltage detection circuit 18 includes a photo coupler 21, an analog switch 22, and a filter circuit 2.
Have three. When the output voltage (PWM voltage) from the power switching circuit 17 is input to the voltage detection circuit 18, the photo coupler 21 changes its rising and falling edges.
To detect. By using the photocoupler 21, it is possible to electrically insulate the high voltage inverter device side power supply and the voltage detection circuit side power supply.

The detection signal from the photocoupler 21 is input to the analog switch 22 as a timing signal to drive the analog switch 22. As a result, the PWM voltage detection signal normalized by the positive and negative reference voltages is obtained from the analog switch 22. The PWM voltage detection signal is input to the filter circuit 23, demodulated, and output to the subtractor 12 as a voltage detection signal.

[0015]

According to the present invention, the detection means for detecting the output voltage is provided and the voltage command signal is corrected based on the detection result, so that stable rotation of the electric motor can be obtained even at low speed driving. Be done.

In particular, as the frequency of the PWM modulation carrier, which is a recent tendency, is further increased, the influence of the dead time of the inverter device becomes more and more significant. Therefore, the inverter device of the present invention is very effective.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a circuit diagram of a voltage detection circuit used in the voltage source inverter device of FIG.

FIG. 3 is a block diagram of a conventional voltage source inverter device.

[Explanation of symbols]

 11 voltage command generation circuit 12 subtractor 13 voltage controller 14 PWM modulation circuit 15 dead time generation circuit 16 base drive circuit 17 power switching circuit 18 voltage detection circuit 21 photocoupler 22 analog switch 23 filter circuit 31 voltage control unit 32 power switching circuit 33 voltage command generation circuit 34 PWM modulation circuit 35 dead time generation circuit 36 base drive circuit 37 AC motor

Claims (1)

[Claims] 1. In response to a command from a voltage command generating circuit,
A voltage type inverter device for generating an output voltage based on the command to drive an AC electric motor, wherein a power switching circuit for generating the output voltage and dead for preventing a short circuit between upper and lower arms of the power switching circuit. A voltage type inverter device having a dead time generation circuit for generating time is provided with voltage detection means for detecting the output voltage and command correction means for correcting the command based on a detection signal from the voltage detection means. A voltage source inverter device characterized in that