JP2001197732A - Control device for semiconductor power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device suited in the case a plurality of sets of semiconductor power converter circuits of the same circuit constitution for a DC current output are operated in parallel. SOLUTION: An adjusted arithmetic value of a current with a detection value of an output current in a main semiconductor power converter circuit 10 serving as the preset value in controlled circuits 70, 80 for performing master slave control by through a control device is multiplied by as many times as the gain in gain adjusters 71, 81, a value adding this gain times value and the adjusted arithmetic value in a main control circuit 40 serves as a signal wave, to apply PWM calculation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a semiconductor power conversion device for supplying a desired direct current to equipment such as electrolysis, metal surface treatment, heating and arc melting.

[0002]

2. Description of the Related Art A semiconductor power converter used for equipment such as electrolysis, metal surface treatment, heating, and arc melting has a capacity of 5k.
It has a function of outputting a direct current of A to 30 kA. Therefore, this semiconductor power conversion device has a circuit configuration in which a plurality of semiconductor power conversion circuits are connected in parallel mainly from the relation of the rated output current value of the semiconductor element.

FIG. 3 is a circuit configuration diagram showing a conventional example of a semiconductor power converter in which three chopper circuits as a semiconductor power converter are connected in parallel as a semiconductor power converter of this type and a control device therefor.

In FIG. 3, 1 is a DC power supply, 2 is a semiconductor power conversion device, 3 is a control device for controlling the semiconductor power conversion device 2, and 4 is a DC current value output from the semiconductor power conversion device 2 to the control device 3. The output setter 5 to be set indicates a load, and the semiconductor power converter 2 includes a chopper circuit 10,
The control device 3 includes a control circuit 40 for controlling the chopper circuit 10, a control circuit 50 for controlling the chopper circuit 20, and a control circuit 60 for controlling the chopper circuit 30.

As shown in FIG. 3, the chopper circuits 10, 2
0, 30 have the same circuit configuration, and IGBTs 11, 21, 21
31, the reflux diodes 12, 22, 32, the reactors 13, 23, 33, and the capacitors 14, 24, 34
And DCCTs 15 and 2 for detecting respective output currents
5, 35.

Similarly, the control circuits 40, 50, and 60 have the same circuit configuration (in FIG. 3, the internal circuit configuration of the control circuit 60 is omitted).
Current regulators 41, 51, (61) for making the deviations from the detection values obtained by the CTs 15, 25, 35 zero, and a saw-tooth wave for generating a saw-tooth wave as a carrier wave in a PWM operation to be described later. Devices 42, 52, (62) and current controller 4
1, 51, and (61) are used as signal waves, and a PWM operation is performed using the signal waves and the respective carrier waves described above, and IGBTs 11, 21, 3, and 3 are performed based on the operation results.
1 PWM operation units 43 and 5 for turning on and off, respectively
3, (63).

The operation of the semiconductor power conversion device 2 and the control device 3 shown in FIG. 3 is described by using a PWM arithmetic unit 43 shown in FIG.
With reference to the operation waveform diagram of the arithmetic unit 53 (PWM arithmetic unit 6
3 is omitted), which will be described below.

[0008] In FIG. 4, in the PWM calculator 43,
As shown in (a), a comparison operation is performed between the sawtooth wave as a carrier wave from the sawtooth wave generator 42 and the signal wave from the current regulator 41, and the result of the operation is used to obtain I as shown in (b).
An on / off signal to the GBT 11 is generated, and the PW
The M calculator 53 includes a sawtooth wave generator 5 as shown in FIG.
A comparison operation is performed between the saw-tooth wave as the carrier wave from the second and the signal wave from the current controller 51, and the calculation result indicates that
As shown in (d), an on / off signal to the IGBT 21 is generated.

[0009]

In the operation waveform diagram shown in FIG. 4, when both IGBT11 and IGBT21 are on, DC power supply 1 → IGBT1 shown in FIG.
Current flows through the path of 1 → reactor 13 → load 5 → DC power supply 1 and the path of DC power supply 1 → IGBT 21 → reactor 23 → load 5 → DC power supply 1. In addition, IGBT11
When both the IGBT 21 and the IGBT 21 are off, current flows through the route of the freewheel diode 12 → reactor 13 → load 5 → freewheel diode 12 and the freewheel diode 22 → reactor 23 → load 5 → freewheel diode 22 shown in FIG. Flows.

However, in the operation waveform diagram shown in FIG. 4, the semiconductor power conversion circuits 10, 20, and 20 shown in FIG.
Variations in circuit constants among the control circuits 40, 50, 6
Due to subtle differences in control constants between 0, for example, IGB
During a period in which T11 is off and IGBT21 is on, as shown in FIG. 5, DC power supply 1 → IGBT21 → reactor 23
A so-called circulating current also flows through the path from the reactor 13 to the reflux diode 12 to the DC power supply 1, making the control operation unstable due to the circulating current, and in some cases, causing an overcurrent state, and the semiconductor power converter operates. Sometimes it became impossible.

Conventionally, as a measure for suppressing the circulating current, the inductance value of each of the reactors 13, 23, and 33 has been increased, but as a result, a new semiconductor power converter is required to be enlarged. Problems arise.

An object of the present invention is to provide a control device for a semiconductor power conversion device capable of suppressing a circulating current without increasing the inductance value of the reactor.

[0013]

According to the present invention, an input side and an output side of a plurality of semiconductor power converters having the same circuit configuration are connected in parallel to each other, and any one of the plurality of semiconductor power converters is connected. One is a main semiconductor power converter, and the other is a semiconductor power converter that is a slave semiconductor power converter. A DC power supply connected to the input side is connected to the DC power supply via each of the semiconductor power converters. In a control device for a semiconductor power converter that converts a direct current to supply the load from the output side, the control device includes a main control circuit that controls a main semiconductor power converter, and a respective sub-semiconductor power converter. A sub-control circuit for controlling the main control circuit. The main control circuit performs an adjustment operation to make the deviation between the commanded current set value and the output current of the main semiconductor power converter zero. The self-extinguishing type semiconductor element constituting the main semiconductor power converter is turned on and off according to the result of the PWM operation, and the respective sub-control circuits respectively control the sub-semiconductor power corresponding to the output current of the main semiconductor power converter. An adjustment operation for reducing a deviation from the output current of the converter to zero is performed, and a PWM operation of the main control circuit is performed based on a value obtained by adding a value obtained by multiplying the adjustment operation value by a gain and an adjustment operation value of the main control circuit. The self-extinguishing element constituting the slave semiconductor power converter is turned on and off according to the result of the PWM operation on the same carrier. According to the invention,
The main control circuit performs control (master control) based on the current set value, and the respective sub-control circuits perform control (slave control) based on the current value output from the main semiconductor power converter, As described below,
Since the time difference and the phase difference at the time of the ON operation of the corresponding self-arc-extinguishing elements can be minimized, the circulating current between the semiconductor power converters can be minimized. And the semiconductor power converter can be miniaturized.

[0014]

FIG. 1 is a circuit diagram of a semiconductor power conversion device and a control device therefor according to an embodiment of the present invention. The same components as those of the conventional circuit shown in FIG. The reference numerals are attached and the description is omitted.

That is, the point that the circuit configuration of the present invention shown in FIG. 1 is different from the conventional circuit configuration shown in FIG. 3 is that the chopper circuit 10 is a main semiconductor power conversion circuit and the chopper circuit 2
0, 30 are each a sub-semiconductor power conversion circuit, a control circuit 40 for controlling the chopper circuit 10 is a main control circuit,
Slave control circuits 70 and 8 for controlling chobber circuits 20 and 30
0 is newly provided in place of the conventional control circuits 50 and 60.

The slave control circuit 70 and the slave control circuit 80 constituting the control device 6 shown in FIG. 1 have the same circuit configuration (FIG. 1).
The description of the internal circuit configuration of the slave control circuit 80 is omitted.) A current controller that sets a detected value of the DCCT 15 as a set value and sets a deviation between the set value and the detected value obtained by each of the DCCTs 25 and 35 to zero. 51, (61), gain adjusters 71, (81) for multiplying the output value of each of the current adjusters 51, (61) by a gain, and the outputs of the gain adjusters 71 (81) and the main control circuit. Adders 72 and (82) for adding the output of the current controller 41; a sawtooth wave as a carrier wave from the sawtooth wave generator 42 constituting the main control circuit 40; and adders 72 and (82). A PWM operation using each output as a signal wave is performed, and a PW for turning on / off each of the IGBTs 21 and 31 based on the result of the operation.
M arithmetic units 53 and (63) are provided.

The operations of the semiconductor power conversion device 2 and the control device 6 shown in FIG.
With reference to the operation waveform diagram of the arithmetic unit 53 (PWM arithmetic unit 6
3 is omitted), which will be described below.

In FIG. 2, in the PWM calculator 43,
As shown in (a), a comparison operation is performed between the sawtooth wave as a carrier wave from the sawtooth wave generator 42 and the signal wave from the current regulator 41, and the result of the operation is used to obtain I as shown in (b).
On / off signals to the GBT 11 are generated, and PWM
The arithmetic unit 53 includes a sawtooth wave generator 42 as shown in FIG.
A comparison operation is performed between the saw-tooth wave as the carrier wave from the adder 72 and the signal wave from the adder 72, and (d)
The on / off signal to the IGBT 21 is generated as shown in FIG.

At this time, the adder 72 shown in FIG.
The adjustment width of the signal wave output from (82) is expressed by the following equation (1).
, The gains of the gain adjusters 71 and (81) are adjusted.

## EQU1 ## Adjustment range (%) = ± (C _eff × ΔVc / voltage of DC power supply 1) × 100 (1) where ΔVc is the maximum value of the output voltage difference between chopper circuits 10, 20, and 30 ( C _eff is determined from the control response and is usually about 2-5.

For example, when the voltage of the DC power supply 1 is 500 volts, the maximum value is usually 5 volts or less.
_Assuming that _eff is 5, the adjustment range of the above equation (1) is ± 5%.

[0021]

According to the present invention, the main control circuit performs control based on the current set value (master control), and the respective sub-control circuits control based on the current value output from the main semiconductor power converter (slave control). ) Can minimize the circulating current between the semiconductor power converters, so that the inductance value of each reactor is about 5% of the conventional value, and in the master-slave control,
As is well known, the operation of adjusting the control constant of each control circuit is also simplified.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a control device of a semiconductor power conversion device showing an embodiment of the present invention.

FIG. 2 is a waveform chart illustrating the operation of FIG.

FIG. 3 is a circuit configuration diagram of a control device of a semiconductor power conversion device showing a conventional example.

FIG. 4 is a waveform chart for explaining the operation of FIG. 3;

FIG. 5 is a circuit diagram illustrating the operation of FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2 ... Semiconductor power converter, 3,6 ... Control device, 4 ... Output setting device, 5 ... Load, 10,20,30 ...
Chopper circuit, 11, 21, 31 ... IGBT, 12, 2
2, 32 reflux diode, 13, 23, 33 reactor, 14, 24, 34 condenser, 15, 25, 3
5 DCCT, 40, 50, 60 control circuit, 41, 5
1, 61 ... current regulator, 42, 52, 62 ... sawtooth wave generator, 43, 53, 63 ... PWM calculator, 70, 80 ...
Slave control circuit, 71, 81 ... gain adjuster, 72, 82 ...
Adder.

Claims (1)

[Claims] An input side and an output side of each of a plurality of semiconductor power converters having the same circuit configuration are connected in parallel with each other, and one of the plurality of semiconductor power converters is a main semiconductor power converter. The other is a semiconductor power conversion device as a slave semiconductor power converter, the DC power supply connected to the input side through the respective semiconductor power converter to convert to a desired DC current and output the A control device for a semiconductor power converter that supplies a load from a side, the control device includes a main control circuit that controls a main semiconductor power converter, and a slave control circuit that controls each of the slave semiconductor power converters. The main control circuit performs an adjustment operation to reduce the deviation between the commanded current set value and the output current of the main semiconductor power converter to zero, and obtains a PWM operation result based on the adjustment operation value. Turning on and off a self-extinguishing type semiconductor element constituting the main semiconductor power converter, wherein each of the slave control circuits outputs an output current of the corresponding slave semiconductor power converter corresponding to an output current of the master semiconductor power converter. And an adjustment operation for reducing the deviation of the adjustment control value to zero, and based on a value obtained by adding a value obtained by multiplying the adjustment operation value by a gain to the adjustment operation value of the main control circuit, the PWM operation on the same carrier as the PWM operation of the main control circuit is performed. A control device for a semiconductor power conversion device, characterized in that a self-extinguishing element constituting said sub-semiconductor power converter is turned on and off according to a calculation result.