JPH02276475A - Power conversion device - Google Patents

Abstract

PURPOSE:To restrain the fluctuation of a terminal voltage by changing the amplitude of a carrier signal and the like by a correcting value based on a DC signal system. CONSTITUTION:The PWM converter 4 of a power conversion device is inserted between a DC signal system including a smoothing capacitor 5 and an AC signal system including a transformer 1 and a reactor 2 to convert AC current into DC current. The output of the PWM converter 4 is supplied to an inverter 6 through the smoothing capacitor 5. Further, the DC signal system is provided with a voltage detector 20 while a controller is constituted of an automatic voltage regulator 8, an automatic current regulator 10, a comparator 11, a subtracter 13, a carrier generator 18 and the like. A correcting value, in inverse proportion to a difference, is outputted by the subtracter 13 to change the amplitude of a carrier signal through an adder 16.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power conversion device and a control method thereof, and in particular,
The present invention relates to a power conversion device suitable for controlling a switching element group inserted between a DC signal system and an AC signal system including a smoothing capacitor using a pulse width modulation signal, and a control method thereof.

[Conventional technology]

Various types of power conversion devices are known that are composed of switching elements such as transistors and thyristors. Among these power conversion devices, those in which the switching elements are controlled by pulse width modulation signals are based on forward conversion. Electric operation and regenerative operation through reverse conversion are possible. Conventional devices of this type include, for example, the target terminal voltage of a smoothing capacitor connected in parallel to a PWM converter, as described in Hitachi Review Vol. 65, No. 4 (1983), pages 13 to 14. A current command is generated based on the deviation between the target voltage command indicating the output voltage of the smoothing capacitor, and this current command is multiplied by the AC voltage signal on the input side of the PWM converter to generate a three-phase AC current command. A 3-phase AC voltage command is generated based on the deviation between the phase AC current command and the 3-phase AC current on the input side of the PWM converter, and the 3-phase AC voltage command is compared with a carrier wave signal of constant amplitude. The switching element of the PWM converter is configured to be controlled by a corresponding pulse width modulation signal.

This type of device is disclosed in Japanese Patent Application Laid-open Nos. 57-52384, 116974-1982 and 62-2.
No. 10866 is mentioned.

[Problem to be solved by the invention]

However, in the above conventional technology, no consideration is given to the response delay of the signal system for generating the three-phase AC voltage command, and it is difficult to maintain the output voltage of the PWM converter at the set voltage using the pulse width modulation signal. The capacitance of the capacitor must be increased. In other words, if the capacity of the smoothing capacitor is reduced, there will be a response delay in the signal system that generates the three-phase AC voltage command, especially when the terminal voltage of the smoothing capacitor increases due to regenerative operation. There is a risk that excessive voltage may be applied to the PWM converter or the switching elements of the inverter connected to the PWM converter.

An object of the present invention is to provide a power conversion device and a control method thereof that can suppress fluctuations in the terminal voltage of a smoothing capacitor.

[Means to solve the problem]

To achieve the above object, the present invention has a first device including a switching element group inserted between a DC signal system and an AC signal system including a smoothing capacitor, and receives a pulse width modulated signal. A power conversion means that converts AC power into DC power by operating a switching element group, a voltage detection means that detects the terminal voltage of the smoothing capacitor, an AC signal detection means that detects the amount of electricity in the AC signal system, and a smoothing capacitor. a command signal generation unit that receives a target voltage command indicating a target terminal voltage of the target terminal voltage and a detection output of the voltage detection means, and generates an AC voltage command signal for suppressing these deviations to zero according to the detection output of the AC signal detection means; With means.

A correction value output means that compares the target voltage command and the detection output of the voltage detection means and outputs a correction value that is inversely proportional to the deviation between the two; and a carrier wave output means that outputs a carrier signal obtained by adding the correction value to a reference carrier signal. The power converter is configured with a pulse width modulation signal generating means that compares the carrier wave signal and the AC voltage command signal and outputs a pulse width modulation signal to the switching element group according to the comparison result. .

The second device has a switching element group inserted between a DC signal system including a smoothing capacitor and an AC signal system, and operates the switching element group in response to a pulse width modulation signal to convert AC power into DC power. a power conversion means for converting into
Voltage detection means for detecting the terminal voltage of the smoothing capacitor;
AC signal detection means for detecting the amount of electricity in the AC signal system, and an AC voltage command signal for receiving the target voltage command indicating the target terminal voltage of the smoothing capacitor and the detection output of the voltage detection means and suppressing the deviation thereof to zero. a command signal generation means for generating the voltage according to the detection output of the AC signal detection means; and a correction value output means for comparing the target voltage command and the detection output of the voltage detection means and outputting a correction value proportional to the deviation between the two. , the command signal modification means for modifying the AC voltage command signal based on the correction value, the carrier wave output means for outputting the reference carrier signal, and the output signal of the reference carrier wave signal and the command signal modification means are compared, and based on the comparison result. A power conversion device is configured, comprising pulse width modulation signal generation means for outputting a corresponding pulse width modulation signal to a switching element group.

The third device has a switching element group inserted between a DC signal system including a smoothing capacitor and an AC signal system, and operates the switching element group in response to a pulse width modulation signal to convert AC power into DC power. a power conversion means for converting into
Voltage detection means for detecting the terminal voltage of the smoothing capacitor;
AC signal detection means for detecting the amount of electricity in the AC signal system, and an AC voltage command signal for receiving the target voltage command indicating the target terminal voltage of the smoothing capacitor and the detection output of the voltage detection means and suppressing the deviation thereof to zero. a command signal generating means that generates a command signal according to the detected output of the AC signal detecting means, and a correction value that is inversely proportional to the deviation between the two by comparing a reference value of the carrier wave signal and the detected output of the voltage detecting means.

a correction value output means for outputting the correction value; and a carrier wave output means for outputting a carrier signal obtained by adding the correction value to a reference carrier signal;
Comparing the carrier signal and the output signal of the command signal modification means,
The present invention constitutes a power conversion device including pulse width modulation signal generating means for outputting a pulse width modulation signal to a switching element group in accordance with the comparison result.

As a first method, when generating a pulse width modulation signal for a switching element group inserted between a DC signal system and an AC signal system including a smoothing capacitor, a target voltage command indicating the target terminal voltage of the smoothing capacitor An AC voltage command signal to suppress the deviation from the terminal voltage of the capacitor to zero is generated based on the electrical quantity of the AC signal system, and the magnitude of the amplitude of the AC voltage command signal and carrier wave signal is compared, and the comparison result is A pulse width modulation signal is generated from , the operation of the switching element group is controlled by this pulse width modulation signal, and when the terminal voltage of the smoothing capacitor fluctuates, a correction value inversely proportional to the difference between the terminal voltage of the smoothing capacitor and the target terminal voltage is generated. This method employs a power converter control method that changes the amplitude of the carrier signal.

As a second method, when generating a pulse width modulation signal for a switching element group inserted between a DC signal system including a smoothing capacitor and an AC signal system, a target voltage command indicating the target terminal voltage of the smoothing capacitor and a smoothing An AC voltage command signal to suppress the deviation from the terminal voltage of the capacitor to zero is generated based on the electrical quantity of the AC signal system, and the magnitude of the amplitude of the AC voltage command signal and carrier wave signal is compared, and the comparison result is A pulse width modulation signal is generated from , the operation of the switching element group is controlled by this pulse width modulation signal, and when the terminal voltage of the smoothing capacitor fluctuates, a correction is made in proportion to the difference between the terminal voltage of the smoothing capacitor and the target terminal voltage. This method employs a power converter control method that changes the amplitude of the AC voltage command signal depending on the value.

[Effect]

During steady state, a pulse width modulation signal is generated based on the comparison result between the AC voltage command signal and the carrier wave signal to control the terminal voltage of the smoothing capacitor to a constant voltage. - On the other hand, when the terminal voltage of the smoothing capacitor fluctuates, before generating the AC voltage command signal, a pulse width modulation signal is generated by changing the magnitude of the carrier signal according to the fluctuation of the smoothing capacitor terminal voltage.

In other words, the sudden change in the terminal voltage of the smoothing capacitor is suppressed by changing the magnitude of the carrier signal, and the carrier signal is returned to its original magnitude from the point when the terminal voltage is maintained at a steady value. Even if there is a response delay in the system that generates the signal.

The terminal voltage can be maintained at a constant voltage by changing the magnitude of the carrier wave signal according to fluctuations in the terminal voltage.
It becomes possible to reduce the capacity of the smoothing capacitor. Furthermore, when the terminal voltage fluctuates, even if the magnitude of the AC voltage command signal is forcibly changed to generate a pulse width modulation signal while the magnitude of the carrier wave signal is kept constant, It is also possible to immediately maintain the terminal voltage at a constant voltage.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, a PWM converter 4 has a switching element such as a transistor, a diode, etc., and is inserted between a DC signal system including a smoothing capacitor 5 and an AC signal system including a transformer 1 and a reactor 2. It is configured as a power conversion means that receives a signal and operates a transistor to convert AC power to DC power. Since this PWM converter 4 converts power using a PWM signal, harmonic components of the power supply frequency can be suppressed, and the PWM signal enables electric operation by forward conversion and regenerative operation by inverse conversion. The output power of the PWMm converter 4 is supplied to an inverter 6 via a smoothing capacitor 5. The AC signal system is also provided with an AC voltage detector 19 and a three-phase AC current detector 3 as AC signal detection means for detecting the amount of electricity in the AC signal system.
The output of the three-phase alternating current detector 3 is supplied to the automatic current regulator 10.

The DC signal system is provided with a voltage detector 20 as a voltage detection means for detecting the terminal voltage of the smoothing capacitor 5, and the detection output of the voltage detector 20 is supplied to the automatic voltage regulator 8 and the subtracter 13. There is.

That is, the detection output of each detector is supplied to a control device for controlling the PWM converter 4.

This control device includes a voltage command unit 7, an automatic voltage regulator 81, a multiplier 9, an automatic current regulator 10, a comparator 11, and an M dynamic circuit 1.
2. It consists of a subtracter 13, an amplifier 14, a reference voltage generator 15, an adder 161, a multiplier 17, and a carrier wave generator 18, and the output signal of the drive circuit 12 is converted into a PWM signal.
The signal is supplied to each transistor of the WM converter 4.

The voltage command unit 7 is configured to output a DC target voltage command indicating the target terminal voltage of the smoothing capacitor 5, and the target voltage command is supplied to the automatic voltage regulator 8 and the subtractor 13. The automatic voltage regulator 8 generates a current command according to the deviation between the target voltage command and the detection output of the voltage detector 20, and outputs this current command to the multiplier 9. This current command is a direct current signal, and depending on its polarity and magnitude, it commands the PWM converter 4 to perform electric operation or regenerative operation. For example, when the polarity of the current command is positive, the PWM converter 4 is commanded to perform regenerative operation.

The multiplier 9 multiplies the current command and the detection output of the AC voltage detector 19 to generate a three-phase AC command indicating the instantaneous value of the current,
A three-phase AC command is output to the automatic current regulator 10. The automatic current regulator 10 generates a three-phase AC voltage command signal for suppressing the deviation between the three-phase AC command and the detection output of the three-phase AC current detector 3 to zero, and converts the AC voltage command signal into a comparator 11. It is designed to output to. The second AC voltage command is generated as a command value for specifying the input terminal of the PWM converter 4. For example, the PWM converter 4
When the input voltage of the transformer 1 is commanded to be higher than the voltage on the input side of the transformer 1, a current flows from the PWM converter 4 to the transformer 1 side.
Regenerative operation is performed.

Conversely, if the command is to make the input voltage of the PWM converter 4 lower than the voltage on the input side of the transformer 1, the PWM
A current flows to the converter 4 side, and the PWM converter 4 is operated electrically. That is, the automatic voltage regulator 81, multiplier 9, and automatic current regulator 1o are configured as command signal generating means.

The comparator 11 compares the carrier wave signal (IKH2) from the 1 multiplier 17 with the AC voltage command, as shown in FIG. 2(A), and generates a PWM signal according to the comparison result. , this PWM signal is supplied to each transistor of the PWM converter 4 via the drive circuit 12.

That is, comparator 11. The drive circuit 12 is configured as a pulse radiation modulation signal generating means.

The multiplier 17 is supplied with the carrier wave signal from the carrier wave generator 18, and is also supplied with the DC voltage from the reference voltage generator 15 and the amplifier 14 through the adder 16. Subtractor 13
DC voltage is supplied from the The subtracter 13 is configured as a correction value output means that outputs a correction value that is inversely proportional to the deviation between the target terminal voltage and the detection output of the voltage detector 20, and outputs this correction value to the adder 16 via the amplifier 14. It is supposed to be done. Namely.

The subtracter 13 outputs a negative voltage when the terminal voltage of the capacitor 5 becomes higher than the target terminal voltage.

Conversely, when the terminal voltage becomes lower than the target terminal voltage, a positive signal is output. and subtractor 1
The output signal of 3 is amplified by an amplifier 14 and then added to the DC voltage from a reference voltage generator 15 by an adder 16, and the output signal of 0 is supplied to a multiplier 17. A carrier wave signal obtained by adding the reference voltage and correction value from the adder 16 to the reference carrier wave signal is output. That is, the multiplier 17 and carrier wave generator 18 are configured as carrier wave output means.

In the above configuration, when a PWM signal is input to the PWM converter 4 based on the target voltage command, AC power is converted to DC power, and the DC power is supplied to the inverter 6 via the smoothing capacitor 5. That is, when electric operation is commanded based on the current command, DC power is sequentially supplied to the inverter 6.

On the other hand, the load condition of the inverter 6 changes, and the inverter 6
When the terminal voltage of the smoothing capacitor 5 becomes higher than the target terminal voltage due to regenerative operation, the output voltage of the subtracter 13 becomes negative, and this signal is output to the adder 16 via the amplifier l4. When this signal is added to the reference voltage of the reference voltage generator 15, the level of the DC voltage decreases, and the amplitude of the carrier wave signal decreases. When this carrier wave signal with reduced amplitude is supplied to the comparator 11, the pulse width of the PWM signal changes rapidly, as shown in FIG. 2(B).
Control is performed to make the input voltage of the PWM converter 4 higher than the voltage on the input side of the transformer 1, and the PWM converter 4 is operated in a regenerative manner. As a result, the power of the DC signal system is returned to the AC signal system, and the terminal voltage of the smoothing capacitor 5 decreases.

That is, as shown in FIG.
When the terminal voltage becomes higher than the target voltage command, the amplitude of the carrier wave signal becomes smaller, and the terminal voltage of the smoothing capacitor 5 decreases due to the regenerative operation of the PWM converter 4. When the terminal voltage of the smoothing capacitor 5 is returned to the target terminal voltage, the output of the subtracter 13 becomes zero, and the amplitude of the carrier wave signal returns to its original state.

In this way, in this embodiment, when the terminal voltage of the smoothing capacitor 5 fluctuates, the amplitude of the carrier signal is reduced by the DC signal system prior to the control to generate the AC voltage command, so that the automatic voltage regulator 8. Even if there is a response delay in the multiplier 9 and the automatic current regulator 1o, fluctuations in the terminal voltage of the smoothing capacitor 5 can be instantly suppressed. Therefore, the capacity of the smoothing capacitor 5 can be reduced.

Further, as shown in FIG. 4, a subtracter 13, an amplifier 14
, a divider 21 is provided in place of the reference voltage generator 15, adder 16, and multiplier 17, and the output signal of the voltage detector 20 is divided by the reference voltage of the divider 21, and a correction value inversely proportional to the deviation between them is obtained. By generating a carrier wave signal and outputting a carrier wave signal in addition to the reference carrier wave signal from the carrier wave generator 18 in addition to the reference carrier wave signal from the carrier wave generator 18, the same effect as in the previous embodiment can be obtained. In this case, the multiplier 21 and carrier wave generator 18 constitute correction value output means and carrier wave output means.

On the other hand, an embodiment in which the amplitude of the carrier wave signal is constant and the amplitude of the AC voltage command is varied is shown in FIG.

That is, in FIG. 5, a multiplier 22 is provided between the automatic current regulator 10 and the comparator 11, and an adder 1
6 is input to the multiplier 22, and the output signal of the carrier wave generator 1
The output signal of 8 is input to the comparator 11. Furthermore, the output signal of the subtracter 13 is input to an amplifier 14. This subtracter 1j is the voltage detector 2
The correction value output means outputs a correction value proportional to the deviation between the zero detection output and the target voltage command. That is, when the terminal voltage of the smoothing capacitor 5 becomes higher than the target terminal voltage, the subtracter 13 outputs a signal proportional to this deviation.

Multiplier 22 multiplies the DC signal from adder 16 and the AC voltage command from automatic current regulator 10.

It is configured as a command signal modification means for modifying the AC voltage command signal based on the correction value from the adder 16. Note that the carrier wave generator 18 is configured as a carrier wave output means for outputting a reference carrier wave signal.

In this embodiment, when the terminal voltage of the smoothing capacitor 5 becomes higher than the target terminal voltage, the positive DC voltage increases to the subtracter 13.
The level of the reference voltage output from the reference voltage generator 15 increases.

This DC voltage is supplied to the multiplier 22. This increases the amplitude of the AC voltage command, and the comparator 11 compares the AC voltage command with the increased amplitude with the carrier wave signal of constant amplitude, and the PWM signal according to the comparison result is
The signal is supplied to the M converter 4. In this case, even if the carrier wave signal amplitude is constant, the amplitude of the AC voltage command increases, so
The PWM converter 4 is operated regeneratively by the same control as when the amplitude of the AC voltage command is constant and the amplitude of the carrier wave signal is small, and the terminal voltage of the smoothing capacitor 5 is reduced.

In this way, in this embodiment, even if there is a response delay in the system for generating the AC voltage command, when the terminal voltage of the smoothing capacitor fluctuates, the AC voltage command is adjusted according to the fluctuation of the terminal voltage. Since the amplitude is changed immediately, fluctuations in the terminal voltage of the smoothing capacitor 5 can be suppressed immediately, and the capacity of the smoothing capacitor 5 can be reduced.

Further, when an experiment was conducted to compare the conventional apparatus and the apparatus in each of the above embodiments, experimental results as shown in FIGS. 6 and 7 were obtained.

As shown in FIG. 6, the conventional device takes a long time to suppress the rise in the terminal voltage Vc of the capacitor, but as shown in FIG. 7, in the case of the device according to the present invention, , it is understood that the increase in the terminal voltage Vc of the capacitor can be suppressed in a short time.

〔Effect of the invention〕

As explained above, according to the present invention, since the amplitude of the carrier signal or the amplitude of the AC voltage command is changed according to the correction value generated based on the DC signal system, there is a response delay in the system that generates the AC voltage command. Even if there is a
It becomes possible to reduce the capacity of the smoothing capacitor.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
3 is a characteristic diagram showing the relationship between the target voltage command and the amplitude of the carrier wave signal, and FIG. 4 is a configuration diagram showing another embodiment of the present invention, FIG. 5 is a block diagram showing still another embodiment of the present invention, FIG. 6 is a waveform diagram showing the experimental results of the conventional example, and FIG. 7 is a waveform diagram showing the experimental results of the apparatus according to the present invention. 1...Transformer, 3...Three-phase AC current detector. 4... PWM converter, 5... Smoothing capacitor, 6...
... Inverter, 7... Voltage command device, 8... Automatic voltage regulator, 9... Multiplier, 10... Automatic current regulator, 11... Comparator. 12...Drive circuit, 13...Subtractor, 15...Reference voltage generator, 16...Adder. 17... Multiplier, 18... Carrier wave generator, 19...
- AC voltage detector, 20... voltage detector. 21... Divider, 22... Multiplier, 23... Subtractor.

Claims (1)

[Claims] 1. A switching element group inserted between a DC signal system including a smoothing capacitor and an AC signal system, and receiving a pulse width modulation signal to operate the switching element group to generate AC power. A power conversion means for converting to DC power, a voltage detection means for detecting the terminal voltage of the smoothing capacitor, an AC signal detection means for detecting the quantity of electricity of the AC signal system, and a target voltage command indicating the target terminal voltage of the smoothing capacitor. a command signal generating means that receives the detected output of the voltage detecting means and generates an AC voltage command signal for suppressing these deviations to zero according to the detected output of the AC signal detecting means; and a target voltage command and the voltage detecting means. a correction value output means for outputting a correction value that is inversely proportional to the deviation between the two by comparing the detection output of the reference carrier signal, a carrier wave output means for outputting a carrier signal obtained by adding the correction value to a reference carrier signal, and a carrier wave signal and an alternating current voltage. A power conversion device comprising pulse width modulation signal generating means for comparing the pulse width modulation signal with a command signal and outputting a pulse width modulation signal to a switching element group according to the comparison result. 2. Power that has a switching element group inserted between a DC signal system and an AC signal system including a smoothing capacitor, and converts AC power into DC power by operating the switching element group in response to a pulse width modulation signal. A conversion means, a voltage detection means for detecting the terminal voltage of the smoothing capacitor, an AC signal detection means for detecting the electrical quantity of the AC signal system, a target voltage command indicating the target terminal voltage of the smoothing capacitor, and a detection output of the voltage detection means. and a command signal generation means that generates an AC voltage command signal for suppressing these deviations to zero according to the detection output of the AC signal detection means, and compares the target voltage command and the detection output of the voltage detection means. a correction value output means for outputting a correction value proportional to the deviation between the two; a command signal modification means for modifying the AC voltage command signal based on the correction value; a carrier output means for outputting a reference carrier signal; and pulse width modulation signal generation means for comparing the output signal of the command signal modification means and outputting a pulse width modulation signal to a switching element group according to the comparison result. 3. Power that has a switching element group inserted between a DC signal system and an AC signal system including a smoothing capacitor, and converts AC power into DC power by operating the switching element group in response to a pulse width modulation signal. A conversion means, a voltage detection means for detecting the terminal voltage of the smoothing capacitor, an AC signal detection means for detecting the electrical quantity of the AC signal system, a target voltage command indicating the target terminal voltage of the smoothing capacitor, and a detection output of the voltage detection means. and a command signal generation means for generating an AC voltage command signal for suppressing these deviations to zero according to the detection output of the AC signal detection means, and a reference value of the carrier wave signal and the detection output of the voltage detection means. A correction value output means for comparing and outputting a correction value inversely proportional to the deviation between the two, a carrier wave output means for outputting a carrier wave signal obtained by adding the correction value to a reference carrier wave signal, and an output signal of the carrier wave signal and command signal correction means. and a pulse width modulation signal generating means for outputting a pulse width modulation signal to the switching element group according to the comparison result;
A power converter equipped with 4. When generating a pulse width modulation signal for a switching element group inserted between a DC signal system including a smoothing capacitor and an AC signal system, the target voltage command indicating the target terminal voltage of the smoothing capacitor and the terminal voltage of the smoothing capacitor are An AC voltage command signal is generated based on the electrical quantity of the AC signal system to suppress the deviation from This pulse width modulation signal is used to control the operation of the switching element group, and when the terminal voltage of the smoothing capacitor fluctuates, the carrier wave signal is adjusted with a correction value inversely proportional to the difference between the terminal voltage of the smoothing capacitor and the target terminal voltage. A control method for a power conversion device that changes amplitude. 5. When generating a pulse width modulation signal for a switching element group inserted between a DC signal system including a smoothing capacitor and an AC signal system, the target voltage command indicating the target terminal voltage of the smoothing capacitor and the terminal voltage of the smoothing capacitor are An AC voltage command signal is generated based on the electrical quantity of the AC signal system to suppress the deviation from A signal is generated, and the operation of the switching element group is controlled by this pulse width modulation signal. When the terminal voltage of the smoothing capacitor fluctuates, the AC voltage is adjusted with a correction value proportional to the difference between the terminal voltage of the smoothing capacitor and the target terminal voltage. A method for controlling a power conversion device that changes the amplitude of a command signal.