JP2658620B2 - Power converter control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for a power converter of an instantaneous waveform control type, comprising a switching element for switching a plurality of times within one cycle, and controlling an instantaneous value of an output voltage with high accuracy. It is about.

[0002]

2. Description of the Related Art FIG. 8 shows a control circuit of a conventional power converter. In FIG. 8, reference numeral 1 denotes a main circuit constituting an inverter for converting DC to AC, and a switching circuit as shown in FIG. For example, a full-bridge inverter composed of the elements S1 and S2 is subjected to pulse width modulation (hereinafter referred to as PWM modulation) with a triangular wave carrier of about 1 to 2 KHz or more. 2, 3 are reactors and capacitors for filters, 5
Is a load, 6a is a detector for the inverter current IA, 6b is a detector for the load current IL, and 6c is a voltage detector for detecting the inverter voltage Vc.

[0003] In the figure, numbers in the 800s indicate that they are components of a control circuit. That is, 801 is an AC reference voltage generation circuit, and 802 is this AC reference voltage Vc * = E
A circuit 803 for generating a current reference command value Ic * = ωCpEcosωt to be passed through a capacitor advanced by 90 ° with respect to sinωt, and 803 is a clock generation circuit serving as a time base for these reference values. 809 is a voltage deviation detection circuit, 810
Generates a control signal Jc in a voltage control circuit. Reference numeral 804 denotes a circuit for generating a load current feedforward control signal IL * based on the detected value IL of the load current. Reference numeral 811 denotes an addition circuit for obtaining a sum IA * of the three signals Ic *, Jc, and IL *. It is. 805 is the inverter current command value IA *
806 is a current control amplifier, and 807 is a low-pass filter for removing a ripple due to PWM modulation of the inverter current IA. Reference numeral 808 denotes a PWM modulation circuit, for example, as shown in FIG.
a, a carrier generation circuit 808b.

Next, the operation will be described. In FIG. 8, the control circuit includes a current minor loop for performing instantaneous current control, and a voltage control loop having a sufficiently fast response. A current command value IA * to be passed by the inverter to output a sine-wave AC voltage is obtained, and the inverter current IA is instantaneously responded to the command value by a current minor loop to obtain an output voltage that follows the AC reference voltage. . That is, the operation of the current minor loop is as follows. The inverter output current IA is detected by the detector 6a to become a detection signal IA1, and the detection signal IA2 from which the ripple component due to the PWM modulation has been removed by the low-pass filter 807.
Becomes An inverter amplifies an error between a current command value IA * to be passed to output a voltage following the AC reference voltage and an inverter current IA by an amplifier 806.
The output signal IE1 of 06 is input to the PWM modulation circuit 808, and the modulation output is added to an inverter to perform PWM control. This current minor loop can make an instant response by reducing the delay and increasing the gain.

[0005] Next, how to determine the current command value IA * and the operation of the voltage control loop will be described. The current to be passed by the inverter is the current Ic flowing through the capacitor 3 and the load current IL. Therefore, the inverter current command value IA * is obtained by adding a correction Jc for minimizing the voltage deviation to the capacitor current command Ic * and the load current command value IL *.

The capacitor current command value Ic * is obtained as follows. The relationship between the voltage Vc of the capacitor and the current Ic is expressed by the following equation.

(Equation 1) Therefore, the current to be passed through the capacitor to obtain a predetermined sine wave voltage is 90 ° with respect to the AC reference voltage Esinωt.
The advanced ωCpEcosωt. As the current loop follows this target value, the inverter can establish the rated voltage under no-load condition. When the no-load voltage is established in this way, the inverter operates with the parallel capacitor connected to the current source, so the characteristics as a low impedance voltage source required for ordinary sine wave inverters Do not have. Therefore, this inverter is configured to make the current minor loop follow the current required by the load at a high speed, so that the inverter becomes a low-impedance voltage source as viewed from the load. The current required by the load has a distorted current waveform including many harmonics in a rectifier load or the like. By giving this distorted waveform as a feedforward signal and outputting it without delay, the inverter looks like a current source,
It is configured to be a voltage source. However, actually, for example, due to the delay or error of the current minor loop, it is not possible to easily follow the harmonic components of the 20th or higher order. Also, a ripple component due to the PWM modulation is output. These high-order harmonic components are supplied by a filter capacitor Cp3 of the inverter so as to obtain a sine wave output.

Next, the purpose and operation of the voltage control loop for outputting the correction Jc will be described. The control system described above performs the load current command value IL * in the feedback control in which the capacitor current Ic follows the predetermined sine wave current Ic *.
Is feed forwarded. A voltage control major loop provided outside the circuit corrects disturbances of the output voltage from the reference voltage due to the following various kinds of fluctuations and uncertain factors, and has a function of stabilizing the system. (1) Disturbance in output voltage due to too large a change rate of load current and the inverter cannot follow (2) Disturbance in output voltage based on current loop deviation due to sudden change in DC input voltage of inverter (3) Element Deviation due to switching delay of inverter and inverter arm short circuit prevention time Td

[0008] Since the voltage is disturbed due to such a cause, the load current becomes different from the original waveform.
If this is detected and feed-forwarded, the voltage will be further disturbed, resulting in an unstable system. In order to correct the instantaneous disturbance of the output voltage due to such a cause and to stabilize the system, the voltage control system outputs a correction signal Jc with a high-speed response to keep the output voltage as a reference. .

By giving the sum of the above three signals Ic *, IL *, and Jc as a current minor loop command value through a limiter, the output current is limited to a value equal to or less than the allowable current of the element. An easy-to-use inverter with suppressed overcurrent.

[0010]

When a conventional control circuit of a converter is used for a converter having a three-phase output, the above-described circuit is constituted by three phases. Here, if the current command value of a certain phase is applied to the limiter, the sum of the output currents of the inverters in the main circuit will always be zero, but the sum of the current command values will not be zero. There is a problem that the output current is not limited.
For example, when the limiter of the inverter current command value is ± 100 A, at a certain moment, 110 A for the U phase and −60 for the V phase.
Assuming that a load through which a current of -50 A flows is connected to the A and W phases, the inverter current command value is limited by the limiter, so that the U phase 100 A, the V phase -60 A, and the W phase -5
Since it becomes 0A, the sum of the inverter current command values does not become zero. The U-phase inverter tries to flow the value of 100 A applied to the limiter, but due to the influence of other phases, as a result, for example, U-phase 105 A, V-phase-57 A,
A current of which sum of W phase −48 A becomes zero flows, and the limiter does not work.

The present invention has been made in order to solve the above-described problems. Even when the current command of the converter is applied to the limiter, the sum of the current commands is made zero and the current according to the current command limiter is reduced. It is an object to obtain a control circuit for a flowing converter.

[0012]

SUMMARY OF THE INVENTION A converter control circuit according to the present invention adds current command values of each phase of a three-phase converter, multiplies the result by a predetermined gain, and outputs a signal of each phase by a signal. It is configured to correct the current command value.

[0013]

The control circuit of the converter according to the present invention operates so that when the current command value of any of the three phases is applied to the limiter, the sum of the three phases of the current command value becomes zero.

[0014]

[Embodiment 1] FIG. 1 shows an embodiment of the present invention.
The same numbers are given to the functions corresponding to those in FIG. FIG. 1 shows a three-phase control circuit composed of three single-phase control circuits shown in FIG. 8, where the suffix U is a component of the U-phase inverter, and the suffix V is the component of the V-phase inverter. The numbers of the components and the suffix W indicate the components of the W-phase inverter. 1U to 1W may be constituted by three single-phase inverters shown in FIG. 9A or may be constituted by three-phase inverters shown in FIG. 9B. The voltage detection circuit 6c is configured to detect a phase voltage of each phase.

Reference numeral 813 denotes an adder for calculating the sum of the three-phase current command values (IA * U to W) output from the limiters 805U to 805. The output of the adder is multiplied by a gain K by an amplifier 814. , Is subtracted from the three-phase current command value before passing through the limiter by the adder / subtractor 811.

Next, the operation of the above embodiment will be described with reference to FIG. When the current command value does not reach the limiter 805, the output of the adder 813 for obtaining the sum of the current command values is always 0, but the current command value of a certain phase, for example, the U-phase current command is positive. , The output of the adder 813 outputs a negative voltage. However, if the output of the adder 813 is multiplied by 814 and multiplied by the gain K and subtracted from the current command value (by the adder / subtractor 811), the U-phase current command applied to the limiter is further corrected in the direction of the limiter. , The current command value does not increase beyond the limiter, while the V-phase and W-phase current commands are corrected in the direction in which the current is suppressed.
In other words, when the current command value of a certain phase is applied to the limiter,
The sum of the three-phase current command values is not reduced to zero, and the correction is applied so as to suppress the current commands of the phases that have not been applied to the limiter. Current can be passed to the transducer.

Embodiment 2 FIG. In the above embodiment, when the voltage control is a control system including integral control such as proportional integral control, the voltage control circuit calculates the deviation between the voltage command and the voltage feedback even when the current command of a certain phase is applied to the limiter. Since the integration is performed, the error of the control amount becomes large, and the voltage control becomes unstable.

The configuration of FIG. 2 is almost the same as that of FIG.
8 is added to the output of the adder 813 for obtaining the sum of the current command values.
The gain is multiplied by a gain K1 at 14 and given to an input of a voltage control circuit 810 by an adder / subtractor 809 as a voltage deviation detection circuit . As a result, since the sum of the current command values is controlled to be zero by the correction signal Jc output from the voltage control circuit 810, a large error in the control amount is suppressed, the voltage control is stabilized, and the current command limiter is controlled. It operates so that the current according to the value flows to the converter.

Embodiment 3 FIG. In the above embodiment, when the current command of a certain phase is applied to the limiter, since the voltage control circuit has a response time constant of the integral control, the control for making the sum of the current commands 0 V cannot be performed at high speed.

The configuration of FIG. 3 is substantially the same as that of FIGS. 1 and 2, except that the output of an adder 813 for obtaining the sum of the current command values is multiplied by a gain K at 814, and an adder / subtractor 811 for obtaining IA * is obtained. by subtracting a result, the multiplying correction cormorants by to 0V the sum of the current command in a high speed, multiplied by a gain K1 at the output 817 of the adder 813, by applying the voltage deviation detector circuit 8 09, the controlled variable In this case, a large error is suppressed, the voltage control is stabilized, and a current according to the limit value of the current command flows to the converter.

Embodiment 4 FIG. In the above embodiment, even when the current command is not applied to the limiter, the correction signal for obtaining the sum of the current command values is given to the control circuit. In this case, there is no problem if the circuit constituting the control system operates ideally. However, when the operational amplifier constituting the circuit has an error due to an offset or the like, this value does not become 0 V and the control becomes unstable. There's a problem.

The configuration of FIG. 4 is configured to provide a correction signal for making the sum of the current commands 0 V only when a certain phase current command is applied to the limiter. In the figure, 815
Is a limiter detection circuit that detects that a certain phase has been applied to the limiter by a signal from 805. For example, FIG.
It is configured as follows. In FIG. 5, the operational amplifier 8
Until the output VO of 05a = ± (VZ / 2), the cathode side voltage V1 of the Zener diode ZD1 =
+ (VZ / 2), which is the voltage of the anode side voltage V2 of the Zener diode ZD1 = − (VZ / 2). However, VZ
= Zener voltage of Zener diode ZD1.

[0023] The output of the arithmetic amplifier 805a to the next V0> +
When the voltage becomes (VZ / 2), the Zener diode ZD
1, the cathode voltage V1 = (the output V0 of the operational amplifier 805a−the diode forward voltage drop VF), and the anode voltage V2 of the Zener diode ZD1 = (the cathode voltage V1−the voltage VZ of the Zener diode ZD1). Next, when the output V0 of the operational amplifier 805a is applied to the limiter, for example, the output V0 of the operational amplifier 805a = +
When the voltage becomes VZ, the potential of the anode voltage V2 of the Zener diode ZD1 tends to rise from the negative potential to the positive side. At this time, D3 turns on, and the anode voltage V2 of the Zener diode ZD1 = diode order. Voltage drop V
It becomes F. Also, the output V0 <-(V
Z / 2), the Zener diode ZD1
Anode voltage V2 = (output V0 of operational amplifier 805a)
+ Diode forward voltage drop VF), Zener diode Z
The cathode side voltage V1 of D1 = (Zener diode ZD
1 (the anode side voltage V2 + the voltage VZ). Next
The output V0 of the operational amplifier 805a has reached the limiter
In this case, for example, when the output V0 of the operational amplifier 805a becomes −VZ, the potential of the cathode side voltage V1 of the Zener diode ZD1 tends to decrease from the positive side potential to the negative side potential. Then, the cathode side voltage V1 of the Zener diode ZD1 = -diode forward voltage drop VF. Limiter detection circuit 81 5, either cathode-side voltage V1 of the Zener diode ZD1 becomes negative voltage,
Or anode voltage V2 of zener diode ZD1 becomes positive voltage is monitored by a comparator 815a, 81 5 b, OR output between 81 5 a and 81 5 b at 81 5 c
Taken, take the OR of the output of each phase of 81 5 c at 81 5 e, by using this output as the output of the limiter detection circuit 815, any of the phases can be detected if Kakare the limiter.

[0024] In this embodiment, in FIG. 4, which one
The output of the limiter detection circuit 81 (5) for detecting that the phase is applied to the limiter, ON the analog switch 816
And, giving a correction signal for the zero sum current command to the pressure decrease adder 811 for obtaining the IA *.

Embodiment 5 FIG. In the embodiment of FIG. 6, a correction signal for making the sum of the current commands 816 the output zero is given to the input of the voltage control circuit 810. Also in this case, it may be applied to both the input of the third embodiment and the <br/> pressure decrease adder 811 the correction signal as well voltage control circuit 810. In these cases, similarly to the second or third embodiment, there is an effect that an error in the control amount is suppressed.

Embodiment 6 FIG. In the above description, the case of a three-phase control system has been described. However, the present invention can be applied to a case where only two phases of a three-phase circuit are controlled. Since the inverter main circuit is a three-wire system, the total value of the three-phase inverter currents is always zero (IAU + IAV + IAW =
0). Therefore, only two of the three phases need to be controlled.

In the embodiment shown in FIG. 7, the three-phase inverter 1U
Voltage control circuit 810, current control circuit 8
06 is provided only for the two phases U and V. in this case,
W-phase current command IA * w is obtained as the sum of U-phase and V-phase current command values. The limiters 805 are provided for three phases and operate in the same manner as in the above embodiment. In addition, P of W phase
The WM command value is supplied to the U-phase and V-phase current control circuits 806U and 806U.
Created from 6V output. This embodiment has an effect that the detection circuit and the control circuit are simplified.

In the above description, the case where the control system is constituted by the analog control system has been described. However, the control system may be constituted by the digital sample value control system, and the same effects as those of the above embodiment can be obtained.

In the above description, the inverter has been described as a power converter. However, the present invention can be applied to any converter of an instantaneous waveform control type such as a high-frequency link type converter using a cycloconverter. Obviously, the same effects as in the above embodiment can be obtained.

[0030]

As described above, according to the present invention, even when the current command value of one phase is applied to the limiter, the output current of the converter is corrected by correcting the sum of the current command values to be zero. Can be set to the limiter value, and an effect of obtaining high accuracy can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control circuit of a power converter according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a control circuit of a power converter according to Embodiment 2 of the present invention.

FIG. 3 is a block diagram showing a control circuit of a power converter according to Embodiment 3 of the present invention.

FIG. 4 is a block diagram showing a control circuit of a power converter according to Embodiment 4 of the present invention.

FIG. 5 is a circuit diagram illustrating a limiter detection circuit according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a control circuit of a power converter according to Embodiment 5 of the present invention.

FIG. 7 is a block diagram showing a control circuit of a power converter according to Embodiment 6 of the present invention.

FIG. 8 is a block diagram showing a control circuit of a conventional power converter.

FIG. 9 is a main circuit diagram of a conventional power converter.

FIG. 10 is a circuit diagram illustrating a pulse width modulation circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter main circuit 2 Reactor 3 Capacitor 5 Load 6 Detection circuit 801 Reference voltage generation circuit 802 Capacitor current command value generation circuit 803 Clock generation circuit 804 Feedforward circuit 805 Limiter 806 Current control circuit 807 Low-pass filter 808 PWM modulation circuit 810 Voltage control circuit 811, 812, 813 Addition / subtraction circuit 814, 817 Amplification circuit 815 Limiter detection circuit 816 Analog switch

Claims (8)

(57) [Claims] The switching element constituting the converter has one switching element.
In a control circuit of a power converter configured to perform switching a plurality of times during a cycle to generate a multi-phase AC output, a value of a current to be output by the converter of each phase is specified.
Make sure that the commanded current command does not exceed the specified value.
When a limiter and at least one of the current command values is applied to the limiter, a signal of a circuit for generating a current command value is output.
So that the sum of the current command values becomes zero.
Control circuit for a power converter, characterized in that a correcting means that. 2. The correction means enters each of the limiters by a signal based on the sum of all current command values via the limiters.
2. The method according to claim 1, wherein the input signal is corrected.
The control circuit of the power converter. 3. A detection circuit for detecting that a limiter has been applied, and the output of the detection circuit causes a current to flow.
Correcting a signal of a circuit for generating a command value ,
A control circuit for a power converter according to claim 1. 4. A switching device comprising one converter
In a control circuit of a power converter configured to perform switching a plurality of times during a cycle to generate a multi-phase AC output, a value of a current to be output by the converter of each phase is specified.
Make sure that the commanded current command does not exceed the specified value.
The limiter and the current command value provided before the limiter
The signal that produces the reference voltage of the output voltage of the converter
And a voltage control circuit that corrects the disturbance from when, when at least one of the current command value is applied to the limiter, the respective voltage control circuit by a signal based on the sum of all current command values through the limiter So that the sum of the current command values becomes zero.
A control circuit for a power converter, comprising: a correction unit that performs correction . 5. A has a detection circuit for detecting that applied to the limiter, a voltage by that there is an output of the detection circuit
5. The control circuit for a power converter according to claim 4, wherein an input signal of the control circuit is corrected. 6. The switching device constituting the converter has one switching element.
In a control circuit of a power converter configured to perform switching a plurality of times during a cycle to generate a multi-phase AC output, a value of a current to be output by the converter of each phase is specified.
Make sure that the commanded current command does not exceed the specified value.
A limiter and the current finger provided before the limiter.
Outputs the signal that makes the reference value and outputs the reference voltage of the converter.
A voltage control circuit that corrects the disturbance from the voltage, and when at least one of the current command values is applied to the limiter , a signal based on the sum of all the current command values via the limiter provides the respective limiters with a signal. The input signal and the input signal of each voltage control circuit are corrected and
Correction means for making the sum of the respective current command values zero
The control circuit of the power converter, wherein a provided. 7. A detection circuit for detecting that a limiter has been actuated.
7. The control circuit for a power converter according to claim 6, wherein a signal input to the power converter and an input signal of the voltage control circuit are corrected. 8. The converter is a three-phase converter, and the current command value is generated only for two phases of the three phases, and the other one phase is for the two phases.
The control circuit for a power converter according to any one of claims 1 to 7, wherein the control circuit is obtained by the sum of: