JPH09312976A - Controller of voltage type converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the oscillation of an AC input current, etc., by providing a limiter which can get signal output which has a specified rate of voltage change, with the output of a proportional-plus-integral controller as input, in a switching system of AC-DC voltage type converter. SOLUTION: A control circuit 20' possesses a change rate limiter 208. Especially, the oscillation of an AC input current can be suppressed by the constitution of a proportional-plus-integral (PI) controller 202' which receives the input of the difference Δ Vd between the DC voltage command Vd* of the output of a subtracter 201 and the DC voltage Vd and a change rate limiter 208 which generates a signal of an AC input current amplitude command Ii*, with the AC input current amplitude command Ii* of the output of the PI controller 202' as input.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching type AC-DC voltage source converter used in a variable voltage variable frequency device for driving an induction motor, various power supply devices, and the like, and more particularly to a PI controller. The present invention also relates to a control device for a voltage source converter that performs switching AC-DC conversion.

[0002]

2. Description of the Related Art In general, a voltage type converter which performs switching AC-DC conversion is shown in FIG.
FIG. 3 shows the configuration of the voltage source converter. 11 to 13 are phase voltages of an AC input power source, 21 to 23, 41 to 43 are reactors, 31 to 33 are capacitors, 51 to 53 are current detectors, and 61 to 66. Is a switching element, 71 to 76 are diodes, 8 is a DC capacitor, 9 is a voltage detector, 10 is a load device, and 20 is a control circuit. In the control circuit 20, 201 and 206 are subtractors, 202 is a PI controller, 203 is an oscillator, 204 is a multiplier, 205 is a current detection circuit, and 207 is a gate controller.

That is, in FIG. 3, the reactor 21,
22 and 23 and capacitors 31, 32 and 33 form a filter circuit to prevent harmonics from being mixed in from an external AC power supply and to cause harmonics generated by switching elements to perform switching operation to flow out to the outside. Is preventing things. Reactors 41, 42, 43 are boosting reactors required for boosting the output DC voltage Vd to a predetermined value. The switching elements 61, 62, 63, 64, 65, 66 are shown as IGBTs here, but GTOs and various transistors are also used. Diodes 71, 72, 73, 74, 75, 76 are anti-parallel diodes for inductive energy processing, and equivalent switching elements such as IGBT and MOSFET transistors are built in. There is also. The DC capacitor 8 has a DC voltage Vd and reduces the ripple component of the switching element output.

In the control circuit 20, the subtractor 201 generates a signal ΔVd between the DC voltage command Vd * and the output of the voltage detector 9 for detecting the DC voltage Vd, and the PI controller 2
02 receives the output of the subtracter 201 and performs P (proportional) I (integral) operation to generate an AC input current amplitude command Ii *. The oscillator 203 detects the phase of the AC input power source and generates a three-phase sine wave signal synchronized with this, and the multiplier 204 is the PI controller 2
The 02 output and the oscillator 203 output are integrated to obtain AC input current commands Iu *, Iv *, Iw *. The current detection circuit 205 is specifically composed of a resistor or the like, and obtains an appropriate conversion level proportional to the actual AC input currents Iu, Iv, Iw. The subtractor 206 generates a signal of the difference between the output of the oscillator 203 and the output of the current detection circuit 205. Gate controller 207
Controls the ignition by setting the ON widths of the switching elements 61 to 66 so that the AC input current commands Iu *, Iv *, Iw * and the AC input currents Iu, Iv, Iw match.

The operation of the apparatus shown in FIG. 3 is well known as a sine wave converter and will not be described in detail.
While keeping d constant, AC input currents Iu, Iv, I
w is a sinusoidal waveform with few harmonics, and the power factor is almost 1
It is normal to say As the gate controller 207, a triangular wave comparison method, a hysteresis comparator method,
A CPU calculation method or the like is generally used.

[0006]

In the prior art of this kind, the DC voltage command Vd * is suddenly changed, and the load device is changed.
If the DC voltage Vd changes suddenly due to the fluctuation of 10, the subtracter 201
The output difference ΔVd also changes abruptly, and since the PI controller 202 includes a proportional control unit, the AC input current amplitude command Ii * also changes abruptly.
This is shown in FIG. That is, in FIG. 4, when the DC voltage command Vd * is increased stepwise at time T0, the difference ΔVd increases by the same amount as the change in the DC voltage command Vd *, but thereafter, due to the action of the control circuit. Since the DC voltage Vd rises, it approaches zero. The AC input current amplitude command Ii * sharply rises at the time T0 by the action of the proportional control unit, and then gradually rises by the action of the integral control unit. After that, like the difference ΔVd, the DC voltage Vd decreases and rises to a predetermined value. Since this value is the case where the DC voltage Vd is increased, the time T
It is generally greater than the value before 0. When the electric power of the load device sharply increases and the DC voltage Vd sharply decreases, the same situation is brought about.

By the way, when the AC input current amplitude command Ii * rapidly increases, the amplitudes of the AC input currents Iu, Iv, and Iw also rapidly increase due to the current control action of the control circuit. At this time,
Reactors 21, 22, 23 (Lf) and capacitors 31, 32, 33
The filter circuit based on (Cf) is generally oscillatory because the resistance component (Rf) of the filter and other circuits is small,
The AC input currents Iu, Iv, and Iw have a high-frequency oscillation waveform with a frequency β and a damping time constant α, which increases the current capacity and the withstand voltage is insufficient.
There were various problems such as increased ripple and mixing of higher harmonics. However, the frequency β and the damping time constant α are expressed by the equations (1), (2), and (3). As described above, even when it is steady and stable, vibration is likely to occur due to this during a transition such as a sudden change in amplitude.

Α = Rf / (2Lf) (1) β = √ {ωn (square) −α (square)} (2) ωn = 1 / {√ (Lf・ Cf)} (3)

The object of the present invention, however, is to provide a special device having a function of suppressing the vibration of the AC input current even when the DC voltage command of the switching AC-DC voltage converter changes suddenly or when the load changes suddenly. There is something to offer.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has the following structure. That is, in a switching type AC-DC voltage type converter having a PI controller that receives an error between a DC voltage command value and a DC voltage detection value as an input and obtains an AC input current amplitude command signal, a PI controller output is used as an input to determine a predetermined value. It comprises limiter means for obtaining a signal output having a voltage change rate. More specifically, the AC input current amplitude command Ii * as shown in FIG. 4 is eliminated so that it can be used as shown in FIG. 1 described later. FIG. 1 shows a ramp-like change in the current command value according to the present invention, similar to FIG. 4, where Ii * ′ is an AC input current amplitude command, Δt is a time change, and ΔV is a command value change. Here, assuming that the AC input current amplitude command Ii * ′ is obtained,
Instead of the AC input current amplitude command Ii * as shown in FIG. 4, the AC input current amplitude command Ii * ′ does not have a sudden change portion as shown in the figure, and the oscillation of the AC input current can be suppressed. That is, P
The limiter means for limiting the change rate of the I controller output is provided, and it is effective for limiting (Δt / ΔV) of (time change / command value change) of the AC input current amplitude command to a predetermined value Vp or less. This is the sampling time (T
In the case of performing the digital control of s), it can be realized by limiting the change in one sample to (Vp · Ts) or less.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows the configuration of the essential parts of an embodiment according to the present invention in a manner similar to FIG. 3, and 20 'is a control circuit. In the control circuit 20 ', 201' and 206 'are subtractors and 202'
Is a PI controller, 203 'is an oscillator, 204' is a multiplier, 20
5'is a current detection circuit, 207 'is a gate controller, and 208 is a change rate limiter. That is, in FIG. 2, the control circuit
A change rate limiter 208 is provided at 20 ', and in particular,
FIG. 1 shows the PI controller 202 ′ that receives the difference ΔVd between the DC voltage command Vd * of the subtracter 201 output and the DC voltage Vd as input, and the AC input current amplitude command Ii * of the PI controller 202 ′ output as input. The configuration of the change rate limiter 208 that generates a signal of the AC input current amplitude command Ii * ′ as described above can suppress the oscillation of the AC input current.

[0012]

As described above in detail, according to the present invention, the switching system AC having the LC filter circuit on the AC input power source side to convert the AC input voltage into the DC output voltage and supply the power to the load device is used. -In the DC voltage converter, when the AC input current amplitude command value is created by the PI controller to control the DC voltage, the high frequency vibration of the AC input current is effective even when the DC voltage command suddenly changes or the load suddenly changes. It is possible to provide a device having a simple structure that can be effectively suppressed, and is extremely useful industrially.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a ramp-like change of a current command value according to the present invention.

FIG. 2 is a circuit diagram showing a main configuration of an embodiment according to the present invention.

FIG. 3 is a circuit diagram showing a configuration example of a voltage source converter.

FIG. 4 is a diagram showing waveforms at various points in FIG.

[Explanation of symbols]

 11 Phase voltage of AC input power supply 21 Reactor 31 Reactor 41 Reactor 51 Current detector 61 Switching element 71 Diode 8 DC capacitor 9 Voltage detector 10 Load device 20 Control circuit 20 'Control circuit 202' PI controller 203 'Oscillator 204 'Multiplier 205' Current detection circuit 207 'Gate controller 208 Change rate limiter Iu AC input current Iu * AC input current command Vd DC voltage Vd * DC voltage command ΔVd difference Ii * AC input current amplitude command Ii *' AC input current Amplitude command

Claims (1)

[Claims] 1. A PI controller for obtaining an AC input current amplitude command signal by inputting an error between a DC voltage command value and a DC voltage detection value, and a product of the AC input current amplitude command signal and the AC input power source phase signal. In the voltage type converter which performs switching AC-DC conversion by the gate control of the switching element based on the error between the AC input current command value and the AC input current detection value created by the above, the PI controller output is used as an input. A control device for a voltage-source converter, comprising limiter means for obtaining a signal output having a predetermined voltage change rate.