JPH10257773A - Power converter - Google Patents

Abstract

(57) Abstract: To reduce the fluctuation of the DC output voltage output from a PWM converter device and quickly execute feedback control. A power converter according to the present invention is provided in a PWM converter that inputs AC power and outputs DC power, and performs feedback control so that a DC output voltage output from the PWM converter is substantially equal to a command voltage. A converter control means for calculating a proportional term and an integral term of the current command value based on the command voltage and the DC output voltage, and calculating a current command value based on the proportional term and the integral term; And correcting means for correcting the value of the integral term of the current command value so that the current command value becomes zero when the voltage reaches the upper limit voltage value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter having a PWM converter for inputting AC power and outputting DC power.

[0002]

2. Description of the Related Art A configuration in which a motor or the like is energized and driven by an inverter device has been practically used. A configuration is known in which the DC power supplied to the inverter device is generated by a PWM converter device. For example, Japanese Patent Publication No. Hei.
No. 2,410,795. The PWM converter device includes a converter circuit having a plurality of switching elements, a reactor provided on a power supply line connecting an input terminal of the converter circuit and an AC power supply, and an output terminal of the converter circuit. And a converter control circuit for controlling the switching element of the converter circuit to be turned on / off.

Here, the converter control circuit includes a PW
A function of detecting a DC output voltage (specifically, a voltage between terminals of the smoothing capacitor) Vdc output from the M converter device and performing a feedback control so that the DC output voltage Vdc becomes substantially equal to the command voltage Vdc *. Have. Specifically, the converter control circuit sets the command voltage V
After calculating the voltage difference between dc * and the DC output voltage Vdc,
A current command value I * is calculated based on the voltage difference, and a control signal for performing PWM control of a switching element of the converter circuit is generated using the current command value I *. In calculating the current command value I *, for example, there is a configuration in which a calculator for performing PI (proportional integration) control is used. In this configuration, the current command value I * is calculated based on a proportional term and an integral term. It becomes sum.

[0004]

In the above-described conventional configuration, when the load (the inverter device and the motor) connected to the PWM converter device increases and the current flowing through the load exceeds the current limit value of the PWM converter device,
The DC output voltage Vdc of the PWM converter decreases (see the V1a portion of the curve V1 in FIG. 5). And after this,
When the load decreases, the PWM converter device is controlled to increase the DC output voltage Vdc to the command voltage Vdc *, and the DC output voltage Vdc increases.

At this time, a phenomenon in which the DC output voltage Vdc becomes considerably higher than the command voltage Vdc *, that is, an overshoot has occurred (see the portion V1b of the curve V1 in FIG. 5). Then, the present inventor has searched for the cause of the occurrence of such an overshoot. When the current command value I * is obtained by calculation in a feedback control loop, the integral term of the current command value I * becomes large. It was found that this had a strong effect on the overshoot. After the occurrence of the overshoot, the DC output voltage Vdc decreases again, and the command voltage Vdc is reduced.
* With the command voltage V
The feedback control is performed so as to converge to dc *.

Here, in the above-described conventional configuration, the DC output voltage Vdc output from the PWM converter device is considerably higher than the command voltage Vdc *, so that the withstand voltage of each switching element and the smoothing capacitor of the converter circuit is increased. Therefore, there is a disadvantage that the manufacturing cost is increased accordingly. In addition, since the overshoot is large, it takes a long time until the fluctuated DC output voltage Vdc converges to the command voltage Vdc *, that is, the response of the feedback control becomes slow.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power converter capable of reducing the fluctuation of the DC output voltage output from a PWM converter and increasing the responsiveness of feedback control. is there.

[0008]

A power converter according to the present invention comprises a PWM converter for inputting AC power and outputting DC power, and a DC output provided in the PWM converter and output from the PWM converter. Converter control means for performing feedback control so that the voltage is substantially equal to the command voltage, wherein the converter control means includes a proportional term and an integral term of a current command value based on the command voltage and the DC output voltage. Calculating means for calculating the current command value based on the proportional term and the integral term, and the current command value such that the current command value becomes zero when the DC output voltage reaches the upper limit voltage value. And a correction means for correcting the value of the integral term of the value.

According to the above configuration, when the DC output voltage output from the PWM converter reaches the upper limit voltage value, the value of the integral term of the current command value is corrected so that the current command value becomes zero. With this configuration, the DC output voltage rises only to the upper limit voltage value. Therefore, the fluctuation of the DC output voltage can be minimized, and the withstand voltage of the switching element, the smoothing capacitor, and the like can be reduced. Further, since the overshoot of the DC output voltage is reduced, the time required for the DC output voltage to return to the command voltage is shortened, and the response of the feedback control is accelerated.

In addition, the converter control means includes: a proportional operation means for calculating a proportional term of a current command value by multiplying a difference between the command voltage and the DC output voltage by a proportional gain; Integral operation means for integrating the difference between the current command value and the integral value and multiplying the integral gain to calculate the integral term of the current command value, and adding the proportional term of the current command value and the integral term of the current command value to obtain the current command value. Adding means for outputting a value, and correcting means for correcting a value of an integral term of the current command value so that the current command value becomes zero when the DC output voltage reaches an upper limit voltage value. It is also preferable to configure.

Further, the converter control means integrates a difference between the command voltage and the DC output voltage, and multiplies the integrated value by an integral gain to calculate an integral term of a current command value; A proportional operation means for multiplying the output voltage by a proportional gain to calculate a proportional term of the current command value; and a subtraction means for subtracting the proportional term of the current command value from the integral term of the current command value to output a current command value; A correction means for correcting the value of the integral term of the current command value so that the current command value becomes zero when the DC output voltage reaches the upper limit voltage value. is there.

Further, in each of the above structures, the correction means corrects the value of the integral term of the current command value so that the current command value becomes zero when the DC output voltage reaches the lower limit voltage value. It is even more preferable that such a configuration is adopted.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. First, FIG. 2 shows P for an inverter device for energizing and driving a motor.
FIG. 3 is a diagram schematically illustrating an electrical configuration of the entire device configured to supply DC power from a WM converter device.

As shown in FIG. 2, AC power supply lines 1a, 1b, and 1c are led out of three-phase AC power supply 1, and these AC power supply lines 1a, 1b, and 1c are connected to reactors 2a, 2a, and 2c.
It is connected to the input terminal of the converter circuit 3 via b and 2c. The converter circuit 3 includes a plurality of switching elements, for example, six switching transistors 3
is connected in a three-phase bridge, and a freewheel diode 3b is connected in anti-parallel to each switching transistor 3a. Each of the switching transistors 3a is composed of, for example, an IGBT or an FET.

The output terminal of the converter circuit 3 is connected to a smoothing capacitor 4 and to DC power supply lines 5a and 5b. These DC power lines 5a and 5b are connected to input terminals of the inverter circuit 6. The inverter circuit 6 is configured such that a plurality of switching elements, for example, six switching transistors 6a are connected in a three-phase bridge, and a freewheel diode 6b is connected in anti-parallel to each switching transistor 6a. Each of the switching transistors 6a is composed of, for example, an IGBT or an FET.

The three-phase output terminals 6 u, 6 v, 6 w of the inverter circuit 6 are connected to the windings of the motor 7. This motor 7 includes an induction motor, a brushless motor,
The motor is composed of a motor such as a switched reluctance motor (SR motor) and can be controlled at a variable speed by an inverter device. The rotational speed ω of the motor 7 is, for example, a speed detector 8 comprising a rotary encoder.
Is configured to be detected. The speed detector 8 is configured to detect a rotation speed ω of the motor 7 and output a rotation speed detection signal ω.

On the other hand, the DC output voltage (voltage between terminals of the smoothing capacitor 4) Vdc between the DC power supply lines 5a and 5b is
It is configured to be detected by the voltage detector 9.
The voltage detector 9 is configured to detect a voltage Vdc between the DC power supply lines 5a and 5b and output a voltage detection signal Vdc.

Each phase of the three-phase AC supplied from the three-phase AC power supply 1 is configured to be detected by a power supply phase detector 10 connected to the AC power supply lines 1a, 1b, 1c. The power supply phase detector 10 is configured to detect each phase of the three-phase AC and output a phase detection signal of the three-phase AC. Further, each of the three-phase alternating currents input to the converter circuit 3 is connected to an AC power supply line 1a, 1
b, current detector 11 provided in a portion between reactors 2a, 2b, 2c and converter circuit 3 in 1c
a, 11b, and 11c. The current detectors 11a, 11b, and 11c are configured to detect the current of each phase of the three-phase alternating current input to the converter circuit 3 and output the detected current detection signals.

The switching transistors 3a of the converter circuit 3 are configured to be turned on and off by a converter control means, for example, a converter control circuit 12. This converter control circuit 12
Is an adder / subtractor 13, a voltage control calculator 14, a three-phase multiplier 15a, 15b, 15c and a three-phase adder / subtractor 16a, 16
b, 16c and three-phase current control calculators 17a, 17b, 1
7c and a PWM base drive circuit 18.

Here, the adder / subtractor 13 and the voltage control calculator 14 are circuits for performing voltage feedback control using the voltage Vdc from the voltage detector 9 as a negative feedback amount. In this case, the adder / subtractor 13 adds and subtracts the command voltage Vdc * given from the outside and the voltage Vdc between the DC power supply lines 5a and 5b detected by the voltage detector 9 (V
dc * -Vdc), and outputs the calculation result. And
The voltage control calculator 14 receives the voltage difference (Vdc * −Vdc) output from the adder / subtractor 13 and the voltage Vdc from the voltage detector 9, and based on these inputs the current command value I.
It is configured to calculate p * and output the calculated current command value Ip *. A specific method of calculating the current command value Ip *, that is, a specific configuration of the voltage control calculator 14 will be described later.

The above-mentioned current command value Ip * is a three-phase AC phase signal detected by the power supply phase detector 10,
That is, it is a command value for determining the amplitude of the three-phase sine wave signal. Therefore, the three-phase multipliers 15a, 15b, 15c
Performs a calculation of multiplying a three-phase sine wave signal (each phase signal of three-phase AC) from the power supply phase detector 10 by a current command value Ip * from the voltage control calculator 14, and as a result of these calculations, 3
It is configured to output a phase sine wave current signal.

The three-phase adder / subtracters 16a, 16b, 1
6c and three-phase current control calculators 17a, 17b, 17c
Is a circuit for configuring a current control loop (the current control loop is a minor loop) using the current signals from the current detectors 11a, 11b, and 11c as a negative feedback amount. In this case, the adder / subtracter 16a, 16b, 16c
Adds or subtracts the three-phase sine wave current signal from the multipliers 15a, 15b, 15c and the current signal from the current detectors 11a, 11b, 11c (specifically, the current Subtract the signal) and output the result of the calculation.

The current control calculators 17a, 17b,
17c receives an output from the adder / subtractor 16a, 16b, 16c, executes an operation for obtaining a signal for instructing a duty of the PWM control based on the output, and executes the operation of the calculated signal (that is, the duty of the PWM control. Command signal)
To the PWM base drive circuit 18.

The PWM base drive circuit 18 receives the output signals from the current control calculators 17a, 17b, 17c and generates a signal for switching each switching transistor 3a of the converter circuit 3 based on these output signals. The switching signals are applied to the bases of the switching transistors 3a. Thereby, each switching transistor 3a of converter circuit 3 is switched (on / off) according to the switching signal, so that feedback control is performed such that voltage Vdc between DC power supply lines 5a and 5b becomes substantially equal to command voltage Vdc *. It is configured to be executed.

In the case of this configuration, the converter circuit 3, the smoothing capacitor 4, the power supply phase detector 10, the current detector 11
a, 11b, 11c, P from the converter control circuit 12, etc.
The WM converter device 19 is configured.

Here, a specific configuration of the voltage control amplifier 14 of the converter control circuit 12 will be described with reference to FIG. As shown in FIG.
Are the proportional operation circuit 20, the integral operation circuit 21, and the addition circuit 2
2 and a correction circuit 23. The proportional operation circuit 20 outputs the voltage difference (Vd
c * -Vdc) is input, an operation of multiplying the input by a proportional gain Kp is executed, and the result of the operation is output as a proportional term Ipp * of the current command value Ip *.
In this case, the proportional operation circuit 20 constitutes the proportional operation means of the present invention.

The integration operation circuit 21 includes an adder / subtractor 13
And outputs the voltage difference (Vdc * -Vdc), which is output for a predetermined set time (integration section).
In addition to performing an integration operation for performing time integration, an operation of multiplying the integration result ((Vdc * −Vdc) / s) by an integration gain Ki is executed, and the operation result is output as an integration term Iip * of the current command value Ip *. It is configured to be. In this case, the integral operation circuit 21 constitutes the integral operation means of the present invention.

The addition circuit 22 is a proportional operation circuit 2
It is configured to perform a calculation for adding the proportional term Ipp * output from 0 and the integral term Iip * output from the integration operation circuit 21 and output the addition result as a current command value Ip *. In this case, the adding circuit 22 constitutes the adding means of the present invention. In the case of the above configuration, the voltage control calculator 14 is configured to output a current command value Ip * by executing a calculation of so-called PI control (proportional-integral control). Incidentally, the proportional operation circuit 20, the integration operation circuit 21 and the addition circuit 22 constitute the operation means of the present invention.

The correction circuit 23 compares the DC output voltage Vdc detected by the voltage detector 9 with a predetermined upper limit voltage value Vdcmax, and Vdc <Vdcmax.
, The current command value Ip output from the addition circuit 22
* Is output as it is. And
The correction circuit 23 determines that Vdc ≧ Vdcmax and Ip *> 0
, The current command value Ip output from the addition circuit 22
* Is output to zero (Ip * = 0), and the value of the integration term Iip * is changed so that the current command value Ip * becomes zero. Specifically, the integration output from the integration operation circuit 21 is performed. It is configured to change the value of the term Iip * to “−Ipp *”.

Here, the control content of the correction circuit 23 is represented by a flowchart as shown in FIG. That is, first, in step S1 of FIG. 3, it is determined whether the DC output voltage Vdc is equal to or higher than the upper limit voltage value Vdcmax (whether Vdc ≧ Vdcmax). Here, if Vdc ≧ Vdcmax, step S1
To "NO" and return without doing anything.

On the other hand, if Vdc ≧ Vdcmax, the process proceeds to “YES” in step S1, and it is determined whether the current command value Ip * is greater than zero (Ip *> 0) (step S1). S2). Here, unless Ip *> 0, the process proceeds to “NO” in step S2, and returns without doing anything. On the other hand, if Ip *> 0, the process proceeds to “YES” in step S2, and changes the value of the integral term Iip * to a value obtained by adding a negative value to the value of the proportional term Ipp * (I
ip * =-Ipp *) processing is performed (step S3). As a result, the current command value Ip * is changed to zero. After the process in step S3, the process returns. Then, while the PWM converter device 19 is operating, the above-described steps S1 to S3 are performed.
Is repeatedly executed.

On the other hand, as shown in FIG. 2, each switching transistor 6a of the inverter circuit 6 connected to the smoothing capacitor 4 of the PWM converter 19 is controlled to be turned on / off by an inverter control circuit 24 as an inverter control means. Is configured. The inverter control circuit 24 is a control circuit having a well-known configuration for performing, for example, PWM control.
Current control calculator 27 and PWM base drive circuit 28
It is composed of

Here, the adder / subtracter 25 and the speed control calculator 26 are circuits for forming a speed control loop using the rotation speed ω of the motor 7 detected by the speed detector 8 as a negative feedback amount. In this case, the adder / subtractor 25 adds / subtracts (ω * −ω) the rotation speed command ω * supplied from the outside and the rotation speed signal ω from the speed detector 8, and outputs the calculation result. Then, the speed control calculator 26 includes the adder / subtractor 2
5 is input (calculated), and is operated (amplified). The calculated motor current command signal _IM * is supplied to the current control calculator 27. The current control calculator 27 is configured to input (calculate) the motor current command signal I _M * from the speed control calculator 26 and to provide the calculated signal to the PWM base drive circuit 28.

Further, the PWM base drive circuit 28
An output signal from the current control calculator 27 is input, and a signal for switching each switching transistor 6a of the inverter circuit 6 is generated based on the output signal.
a. Thereby, each switching transistor 6 of the inverter circuit 6
a is switched, so that the rotation speed ω of the motor 7 is
Is set to be substantially equal to the command rotation speed ω *. In the case of this configuration, an inverter device 29 includes the inverter drive circuit 6, the speed detector 8, the inverter control circuit 24, and the like.

In the above configuration, the PWM converter 19 controls the voltage Vdc between the DC power supply lines 5a and 5b to be maintained at the command voltage Vdc *. Then, the inverter device 29 controls the rotation speed ω of the motor 7 to be maintained at the command rotation speed ω *.

Here, when the motor 7 is operated in the power running mode, the AC power from the three-phase AC power supply 1 is converted into DC power by the PWM converter 19, and the DC power is supplied to the DC power supply lines 5a, 5b. It is supposed to be. The DC power is supplied to the motor 7 by the inverter device 29. On the other hand, when the motor 7 is in the regenerative operation, the electric power generated by the motor 7 is supplied to the DC power supply lines 5a, 5b
(Smoothing capacitor 4), and the supplied DC power is supplied to the three-phase AC power supply 1 by the PWM converter 19.
It is configured to be regenerated.

In the above configuration, since the PWM converter device 19 is used, the power factor on the power source side can be kept at 1, so that the efficiency is increased and the harmonics generated on the power source side are reduced. In addition, since power is regenerated to the power supply side, power consumption can be reduced.

Next, when the PWM converter 19 is started and when the load of the motor 7 fluctuates, the DC output voltage Vd from the PWM converter 19 is
The operation when c is larger than the command voltage Vdc * (when overshoot occurs) will be described with reference to FIGS. First, the PWM converter device 1
The operation at the time of startup of No. 9 will be described with reference to FIG.

As shown in FIG. 4, when the PWM converter 19 is operated, the DC output voltage Vdc rises from the initial voltage Vdc0 (peak value or peak value of the AC power supply 1) as shown by a solid line V2. It rises beyond the command voltage Vdc *. When the DC output voltage Vdc reaches the upper limit voltage value Vdcmax, the process proceeds to “YES” in step S1 of FIG. 3, and further “YES” in step S2.
Then, the value of the integral term Iip * is set to Iip * =-Ipp * (step S3).

As a result, the current command value Ip * output from the voltage control amplifier 14 becomes zero, so that the DC output voltage Vdc does not increase and the DC output voltage Vdc is
As indicated by the middle broken line, the voltage drops and quickly converges to the command voltage Vdc *. Therefore, in the case of the above configuration,
The overshoot of the DC output voltage Vdc is the upper limit voltage value V
dcmax, the conventional configuration (solid line V in FIG. 4)
2, the rise (fluctuation) of the DC output voltage Vdc can be reduced as compared with the overshoot indicated by the V2a portion of FIG.

Next, referring to FIG. 5, when the magnitude of the load of the motor 7 fluctuates, specifically, the load (the inverter device 29 and the motor 7) connected to the PWM converter 19 increases. And the current flowing through the load is PWM
The operation of the converter device 19 when the current limit value is exceeded will be described. In this case, the current flowing through the load is P
When the current limit value of the WM converter device 19 is exceeded, PW
The DC output voltage Vdc of the M converter device 19 decreases (see the V1a portion of the curve V1 in FIG. 5).

Thereafter, when the load decreases, the PWM
Converter device 19 performs control to increase DC output voltage Vdc to command voltage Vdc *. As a result, the DC output voltage Vdc rises and exceeds the command voltage Vdc *. Then, the DC output voltage Vdc is equal to the upper limit voltage value Vdc.
When the maximum is reached, “YES” is determined in step S1 of FIG.
The process proceeds to “YES” in step S2, and the value of the integral term Iip * is set to Iip * = − Ipp * (step S3). As a result, the current command value Ip * output from the voltage control amplifier 14 becomes zero, so that the DC output voltage Vdc does not increase, and the DC output voltage Vdc is reduced as shown in FIG.
As indicated by the middle broken line, the voltage drops and quickly converges to the command voltage Vdc *.

In this configuration, the overshoot of the DC output voltage Vdc is approximately equal to the upper limit voltage value Vdcmax. Therefore, the DC output voltage Vdc is lower than that of the conventional configuration (overshoot indicated by V1a of the solid line V1 in FIG. 5). Rise (fluctuation) can be reduced.

According to this embodiment having such a structure, the PW
When the DC output voltage Vdc output from the PWM converter device 19 exceeds the command voltage Vdc * when the M converter device 19 is started or when the load on the motor 7 is increased, the DC output voltage Vdc overshoots. Is not higher than the upper limit voltage value Vdcmax, so that the amount of increase in the DC output voltage Vdc can be reduced as compared with the conventional configuration. As a result, the PWM converter device 1
9, the withstand voltage of the switching transistor 3a, the smoothing capacitor 4, and the like can be reduced, and the manufacturing cost can be reduced accordingly.

In the above embodiment, the DC output voltage Vd
Since the rise amount (overshoot) of c is small, the time required for the DC output voltage Vdc to return to the command voltage Vdc * (convergence) is shortened. Therefore, the responsiveness of the feedback control of the PWM converter device 19 is improved.

In the above embodiment, the feedback control function of the converter control circuit 12 of the PWM converter device 19 is configured to be realized by the functional blocks as shown in FIGS. 1 and 2. However, the present invention is not limited to this. Instead, the converter control circuit 12 may be configured by a microcomputer, and the feedback control function thereof may be realized by a control program.

Further, in the above embodiment, step S in FIG.
1, it is determined whether or not Vdc ≧ Vdcmax. Instead, Vdc> Vdc
It may be configured to determine whether or not the value is max.
Even in the case of such a configuration, substantially the same control can be performed, so that the same operation and effect can be obtained.

FIGS. 6 and 7 show a second embodiment of the present invention, and the differences from the first embodiment will be described. The same parts as those in the first embodiment are denoted by the same reference numerals. In the second embodiment, a voltage control calculator 30 that performs so-called IP control is used in place of the voltage control calculator 14 that performs PI control, and the voltage control calculator 30 outputs a current command value Ip *. It is configured as follows.

As shown in FIG. 6, the voltage control amplifier 30 comprises an integration circuit 21, an addition / subtraction unit 31, a proportional operation circuit 20, an addition / subtraction unit 32, and a correction circuit 33. The integration operation circuit 21 receives the voltage difference (Vdc * -Vdc) output from the adder / subtractor 13 and performs an integration operation for integrating the voltage difference for a predetermined set time (integration section). Together with this integration result ((Vdc *
-Vdc) / s) is multiplied by the integral gain Ki, and the result of this operation is represented by the integral term Iip * of the current command value Ip *.
It is configured to output as.

The adder / subtractor 31 subtracts the voltage Vdc0, which is the peak value or peak value, of the AC power supply 1 from the DC output voltage Vdc detected by the voltage detector 9, and calculates the subtraction result (Vdc-Vdc0) as a proportional operation circuit. 20. The proportional operation circuit 20 receives the voltage difference (Vdc−Vdc0) output from the adder / subtractor 31 and performs an operation of multiplying the input voltage difference by a proportional gain Kp. This operation result is used as the proportional term of the current command value Ip *. It is configured to output as Ipp *. In this case, the voltage difference (V
dc−Vdc0), since Vdc0 is a constant such as the peak value of the AC power supply 1, the proportional operation circuit 20 realizes a function of substantially multiplying the DC output voltage Vdc by the proportional gain Kp, This constitutes the proportional operation means of the present invention.

The adder / subtractor 32 is provided by the integration operation circuit 2
From the integral term Iip * output from the first
The calculation is performed to subtract a proportional term Ipp * output from 0, and the result of the subtraction is output as a current command value Ip *. In this case, the adder / subtractor 32 constitutes the subtraction means of the present invention.

Further, the correction circuit 33 includes a DC output voltage Vdc detected by the voltage detector 9 and an upper limit voltage value Vdcm.
ax, and when Vdc <Vdcmax, the current command value Ip * output from the addition / subtraction circuit 32 is output as it is. Then, the correction circuit 33
When Vdc ≧ Vdcmax and Ip *> 0, the current command value Ip * output from the addition / subtraction circuit 32 is set to zero (Ip * = 0) and output, and the current command value Ip * becomes zero. The value of the integral term Iip * is changed, specifically, the integral term Iip * output from the integral operation circuit 21.
Is changed to “Ipp *”.

Here, the control contents of the correction circuit 33 are represented by a flowchart as shown in FIG. That is, first, in step S101 of FIG. 7, it is determined whether the DC output voltage Vdc is equal to or higher than the upper limit voltage value Vdcmax (whether Vdc ≧ Vdcmax). Here, if Vdc ≧ Vdcmax, the process proceeds to “NO” in step S101, and returns without doing anything.

On the other hand, if Vdc ≧ Vdcmax, the process proceeds to "YES" in step S101, and the current command value Ip
It is determined whether or not * is greater than zero (whether or not Ip *> 0) (step S102). Here, unless Ip *> 0, the process proceeds to “NO” in step S102, and returns without doing anything. On the other hand, if Ip *> 0, the process proceeds to "YES" in step S102, and the value of the integral term Iip * is changed to the value of the proportional term Ipp * (Ii).
p * = Ipp *) processing is performed (step S103). As a result, the current command value Ip * is changed to zero. After the process in step S103, the process returns.

According to the above configuration, when the PWM converter 19 is started or when the magnitude of the load of the motor 7 fluctuates, the PWM converter 19 is turned on.
May be higher than the command voltage Vdc * (see FIGS. 4 and 5). In such a case, the correction circuit 33 operates as shown in FIG. As a result, the DC output voltage Vdc from the PWM converter device 19 does not exceed the upper limit voltage value Vdcmax, and falls as shown by the broken lines in FIGS. 4 and 5 to quickly converge to the command voltage Vdc *. Become like Therefore, the overshoot of the DC output voltage Vdc can be reduced to about the upper limit voltage value Vdcmax, that is, the overshoot can be reduced, and the response of the feedback control can be quickened.

In the second embodiment, since the IP control is executed by the voltage control calculator 30, the DC output voltage Vdc from the PWM converter 19 is reduced when the PWM converter 19 is started. There is almost no overshoot (overshoot is extremely small).

The configuration of the second embodiment other than the above is the same as that of the first embodiment. Therefore, in the second embodiment, substantially the same operation and effect as in the first embodiment can be obtained. Further, in the second embodiment, various modifications can be made in the same manner as in the first embodiment.

FIGS. 8 to 10 show a third embodiment of the present invention, and the points different from the first embodiment will be described. The same parts as those in the first embodiment are denoted by the same reference numerals. In the third embodiment, the correction circuit 23 of the voltage control calculator 14 is provided with a control function described below (see the flowchart of FIG. 8), and the DC output voltage Vdc output from the PWM converter 19 is a so-called undershoot. When an occurrence occurs, the undershoot is reduced.

First, the undershoot of the DC output voltage Vdc that occurs when the motor 7 performs the regenerative operation will be described with reference to FIG. When the motor 7 performs the regenerative operation, as shown in FIG. 9, a phenomenon that the DC output voltage Vdc temporarily rises and then falls due to the regenerative power and becomes considerably smaller than the command voltage Vdc *, that is, an undershoot occurs ( In FIG. 9, a solid line V3 indicates a portion V3a).
After that, the DC output voltage Vdc is feedback-controlled so as to rise again and converge on the command voltage Vdc *.

On the other hand, in the third embodiment, a lower limit voltage Vdcmin slightly lower than the command voltage Vdc * is set in the correction circuit 23, and the control shown in the flowchart of FIG. Is configured to execute. That is, first, in step S201 of FIG. 8, it is determined whether the DC output voltage Vdc is equal to or lower than the lower limit voltage value Vdcmin (whether Vdc ≦ Vdcmin).
Judge. Here, if Vdc ≦ Vdcmin, the process proceeds to “NO” in step S201, and returns without doing anything.

On the other hand, if Vdc≤Vdcmin, the process proceeds to "YES" in step S201, and the current command value Ip
It is determined whether * is greater than zero (whether Ip * <0) (step S202). Here, unless Ip * <0, the process proceeds to “NO” in step S202, and returns without doing anything. On the other hand, if Ip * <0, the process proceeds to "YES" in step S202, and the value of the integral term Iip * is changed so that the current command value Ip * becomes zero (step S203). Specifically, the integral term Iip
The value of * is changed to a value obtained by adding a negative value to the value of the proportional term Ipp * (Iip * =-Ipp *). This allows
Current command value Ip * is changed to zero. Step S2 above
It is configured to return after the process of 03.

As a result, the DC output voltage Vdc from the PWM converter 19 does not become lower than the lower limit voltage value Vdcmin, but rises as shown by the broken line in FIG. It will converge. Therefore, the undershoot of the DC output voltage Vdc can be reduced to about the lower limit voltage value Vdcmin, that is, the undershoot can be reduced, and the response of the feedback control can be quickened.

As a case where the DC output voltage Vdc undershoots, for example, the DC output voltage Vdc
(Command voltage Vdc *) in some cases. in this case,
As shown in FIG. 10, when the command voltage Vdc * is reduced to the second command voltage Vdc1 *, the DC output voltage Vdc becomes considerably smaller than the command voltage Vdc1 *, that is,
An undershoot occurs (solid line V4 in FIG. 10).
Section V4a). After this, the DC output voltage V
The feedback control is performed so that dc rises again and converges to the second command voltage Vdc1 *.

On the other hand, in the third embodiment, the second lower limit voltage Vdcmin1 which is slightly lower than the reduced command voltage Vdc1 * is set in the correction circuit 23, and the correction circuit 23 Thus, the control is executed substantially the same as the control shown in the flowchart of FIG. In this case, the lower limit voltage Vdcmin described in FIG.
Is replaced with the second lower limit voltage Vdcmin1 to execute the control.

As a result, the current command value Ip * is changed to zero, so that the DC output voltage Vdc does not become smaller than the second lower limit voltage value Vdcmin1.
As indicated by the middle broken line, the second command voltage Vdc increases.
It quickly converges to 1 *. Therefore, the undershoot of the DC output voltage Vdc is reduced to the second lower limit voltage value Vd.
Cin1 or the undershoot can be reduced, and the response of the feedback control can be accelerated.

In the third embodiment, the correction circuit 23
In addition, the function of reducing the overshoot and the function of reducing the undershoot are provided, but instead, only the function of reducing the undershoot may be provided.

Further, the voltage control calculator 30 of the second embodiment
Function of reducing the undershoot of the third embodiment described above (see the flowchart of FIG. 8).
It may be configured to have the same function as. Further, in the case of this configuration, the function of reducing the overshoot may be stopped and only the function of reducing the undershoot may be provided.

[0068]

As is apparent from the above description, the present invention calculates the proportional term and the integral term of the current command value based on the command voltage and the DC output voltage, and executes the current command based on the proportional term and the integral term. Since it is configured to include a calculating means for calculating the value and a correcting means for correcting the value of the integral term of the current command value so that the current command value becomes zero when the DC output voltage reaches the upper limit voltage value, An excellent effect is obtained that the fluctuation of the DC output voltage output from the PWM converter device can be reduced and the feedback control can be executed quickly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a voltage control arithmetic unit and its periphery according to a first embodiment of the present invention;

FIG. 2 is an electrical configuration diagram of the whole PWM converter device and inverter device.

FIG. 3 is a flowchart.

FIG. 4 is a diagram showing a change in voltage when the motor is started.

FIG. 5 is a diagram showing a change in voltage when a current flowing through a load becomes equal to or more than a current limit value of the PWM converter device.

FIG. 6 is a view corresponding to FIG. 1, showing a second embodiment of the present invention;

FIG. 7 is a diagram corresponding to FIG. 3;

FIG. 8 is a view corresponding to FIG. 3, showing a third embodiment of the present invention.

FIG. 9 is a diagram showing a change in voltage during motor regeneration operation.

FIG. 10 is a diagram illustrating a change in voltage when the DC output voltage of the PWM converter device is reduced.

[Explanation of symbols]

1 is a three-phase AC power supply, 2a, 2b and 2c are reactors, 3
Is a converter circuit, 3a is a switching transistor,
4 is a smoothing capacitor, 6 is an inverter circuit, 6a is a switching transistor, 7 is a motor, 9 is a voltage detector,
12 is a converter control circuit (converter control means), 1
3 is an adder / subtractor, 14 is a voltage control calculator, 15a, 15
b and 15c are multipliers, 16a, 16b and 16c are adders / subtracters, 17a, 17b and 17c are current control calculators, 18 is a PWM base drive circuit, 19 is a PWM converter device, and 20 is a proportional calculation circuit (proportional calculation means) , 21 is an integral operation circuit (integration operation means), 22 is an addition circuit (addition means), 23 is a correction circuit (correction means), 24 is an inverter control circuit, 29 is an inverter device, 30 is a voltage control operation unit, 31 is Adder / subtracter 32, adder / subtractor (subtraction means), 3
Reference numeral 3 denotes a correction circuit (correction means).

Claims (4)

[Claims] 1. A PWM converter for inputting AC power and outputting DC power, and a feedback control provided in the PWM converter so that a DC output voltage output from the PWM converter is substantially equal to a command voltage. The converter control means calculates a proportional term and an integral term of a current command value based on the command voltage and the DC output voltage, and calculates the proportional term and the integral term. Calculating means for calculating a current command value based on the term, correction for correcting a value of an integral term of the current command value so that the current command value becomes zero when the DC output voltage reaches an upper limit voltage value. And a power conversion device. 2. A PWM converter for inputting AC power and outputting DC power, and a feedback control provided in the PWM converter so that a DC output voltage output from the PWM converter is substantially equal to a command voltage. A power conversion device comprising: a converter control means that performs a proportional gain on a difference between the command voltage and the DC output voltage by a proportional gain to calculate a proportional term of a current command value; An integration means for integrating a difference between the command voltage and the DC output voltage and multiplying the integrated value by an integration gain to calculate an integral term of the current command value; a proportional term of the current command value and the current command; Adding means for adding the integral term of the value to output a current command value, and when the DC output voltage reaches an upper limit voltage value, the current command value is Power conversion apparatus characterized by being constituted by a correcting means for correcting the value of the integral term of the current command value so that the. 3. A PWM converter for inputting AC power and outputting DC power, and feedback control provided in the PWM converter so that a DC output voltage output from the PWM converter is substantially equal to a command voltage. The converter control means, wherein the converter control means integrates a difference between the command voltage and the DC output voltage, and multiplies the integrated value by an integration gain to obtain an integral term of the current command value. And a proportional operation means for multiplying the DC output voltage by a proportional gain to calculate a proportional term of the current command value, and subtracting the proportional term of the current command value from the integral term of the current command value. Subtracting means for outputting a current command value by means of the DC output voltage, so that the current command value becomes zero when the DC output voltage reaches an upper limit voltage value. Power conversion apparatus characterized by and a correcting means for correcting the value of the integral term of the flow command value. 4. The correction means is configured to correct a value of an integral term of the current command value so that the current command value becomes zero when the DC output voltage reaches a lower limit voltage value. The power converter according to any one of claims 1 to 3, wherein: