JPS61277376A - Starting circuit for pwm converter - Google Patents

Abstract

PURPOSE:To suppress excessive AC input current, by making a DC output voltage command value, in a pattern based on the DC output voltage before starting, as an initial value, on the starting of a PWM converter. CONSTITUTION:The AC power source PS is inputted to a PWM converter (CONV) via a transformer TR, and is converted to DC. The CONV is organized with GTO thyristors T1-T4 and diodes D1-D4, and is controlled by the first and the second compensation circuits 2, 4, a gate amplification circuit 6, and the like so that the DC output voltage VD may be equal to the command value VR. Then, the output step of a hold circuit 7 holding the output voltage VD is connected to a command value generation circuit 8, and the circuit 8 is connected to the first compensation circuit 2. After that, when the output of starting command is generated, then the DC output voltage before starting is read through the hold circuit 7 by the command value generation circuit 8, and the voltage with this initial value is gradually enhanced along with time, and the CONV is arranged to be changeable to generate the final objective output.

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a PWM converter device, and in particular, a startup circuit for a PWM converter device that can perform smooth startup so that the startup current does not become excessive during startup. Regarding.

[Technical background of the invention and its problems]

Advances in semiconductor technology have made it easier to create AC/DC converters and vice versa using thyristors, diodes, etc. However, with the spread of AC/DC converters, improvements in the power factor of AC side power and higher tuning have become necessary. Wave reduction is now required.

In recent years, in order to meet the above requirements, PWM converter devices using switching elements such as gate turn-off thyristors (hereinafter referred to as rGTo thyristors) have been actively developed.

FIG. 3 shows a block diagram of a conventional PWM converter device.

AC mPS is connected to PWM converter C via transformer TR.
It is input to 0NV and converted to DC.

This PWM converter C0NV is GTO thyristor T1
~T4 and diodes D1 to D4. L is AC reactor, CO is filter capacitor,
VDI, VD2 are voltage detectors, CT1 is current detector, V
R indicates a DC output voltage command setter (VR is its command value).

This PWM converter C0NV is controlled by the gate signals of the GTO thyristors T1 to T4 so that the DC output voltage V becomes equal to the DC output voltage command 1iavR.

Here, before the gate signal is output to the GTO thyristors T1 to T4 of the PWM converter C0NV, that is, the PWM
Considering before starting M converter C0NV, GTO
Since diodes D1 to D4 are connected in antiparallel to each of the thyristors T1 to T4, when AC power supply PS is applied, power is supplied via transformer TR, and P
A voltage of a single-phase full-wave rectified waveform is applied to the filter capacitor CO connected to the output side of the WM converter C0NV, and the voltage of the filter capacitor CO is charged to the peak value of the single-phase full-wave rectified waveform.

The voltage of the filter capacitor CO at this time is '2V
(V is the AC voltage output by the transformer TR), the output voltage r- voltage command value vR of the normal PWM converter C0NV is set to be larger than 2V and is amplified in path 2, and the AC voltage Current command fR obtained by multiplying
If the value of is large (and in this state, a starting command is given to the PWM converter and a gate signal is output to the GTO thyristors T1 to T4, an excessive current will flow immediately after starting.

If excessive current flows, GTO thyristors T1 to T4
And there is a possibility that the diodes D1 to D4 may be destroyed. Furthermore, in a PWM converter that is provided with an overcurrent detection circuit, there is a possibility that overcurrent detection will be activated every time the converter is started, which is not preferable as a device.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a PWM converter device that prevents excessive current from flowing when starting the PWM converter.

(Summary of the Invention) In order to achieve the above object, the present invention detects the output voltage of a PWM converter device, and detects the output voltage of a PWM converter device at the time of startup.
The output voltage value of the WM converter is given as an output voltage command of the PWM converter device, and the output voltage command is gradually increased with startup, so that the output voltage of the PWM converter device is controlled to increase to the final target output voltage. This is a startup circuit for a PWM converter device.

[Embodiments of the invention]

FIG. 1 shows a block diagram showing a circuit configuration in an embodiment of the present invention.

The AC power supply PS is connected to the load side via a transformer TR, an AC reactor L, and a PWM converter device. The main circuit of this PWM converter device has the same configuration as shown in FIG. 3, which is shown in FIG.

Therefore, the first voltage detector VD1 installed on the AC input side of the PWM converter device is connected to the multiplication circuit 3,
A second voltage detector VD2 installed on the DC output side of the PWM converter device is connected to the hold circuit 7 and the first compensation circuit 2.

Hold circuit 7 that holds the filter capacitor voltage V.
The output stage of is connected to a DC output voltage command value generation circuit 8 in which the DC output voltage command value increases smoothly and saturates at a constant value as a function of time, and the DC output voltage command value generation circuit 8 is connected to a first compensation circuit 2, and this first compensation circuit 2
and the first voltage detector VD1 is connected to a multiplication circuit 3, and this multiplication circuit 3 and current transformer CT1 are connected to a second compensation circuit 4, and the second compensation circuit 4 and the modulation which is a high frequency triangular wave. A modulated wave generation circuit 5 that outputs a wave is connected to a gate amplifier circuit 6, and this gate amplifier circuit 6 is connected to each gate of the GTO zyristors T1 to T4 of the PWM converter device C0NV.

Next, the operation will be explained.

First, the basic operation of the PWM converter device will be explained.

PWM converter device 1cON that receives AC power from AC power supply PS via transformer TR and reactor L
V is controlled so that the DC voltage at its output stage is kept constant, and the waveform of the AC input current is controlled to be in phase or in phase with the AC input voltage, and closer to a sine wave.

The DC output voltage vo of the PWM converter @cONV detected by the second voltage detector VD2 and the DC output voltage command 1IvR are compared, and the difference is calculated by the first compensation circuit 2.
is input. The output, which has been operationally amplified with an appropriate time delay in the first compensation circuit 2, and the AC input voltage (■) of the PWM converter device detected by the first voltage detection circuit VD1 are multiplied in the multiplication circuit 3, and the AC An input current command value IR is output.

This AC input current command value IR and the AC input current of the PWM converter device C0NV detected by the current transformer CTI are compared and input to the second compensation circuit 4. This second
In the compensation circuit 4, the output which has been operationally amplified with an appropriate time delay is compared with the modulated wave 5 which is a high frequency triangular wave.
The difference is input to the gate amplification circuit 6, and the gate amplification circuit 6tfi and PWM controller t<-evening wave HCONV(1
) An ignition signal is sent to each gate of GTO4t iris T1 to T4.

In the above operation, when the PWM converter device starts up, its DC output voltage detection value ■. When the difference between the DC output voltage command value VR and the DC output voltage command value VR is large, the DC current command value T of the PWM converter device [C0NV calculated by the multiplication circuit 3]
When R becomes large and the PWM converter device C0NV is activated, an excessive alternating current may flow.

Therefore, when starting the PWM converter device C0NV, the starting command is output to the hold circuit 7 and at the same time the second voltage detector VD2 detects the DC output voltage before starting the PWM converter device C0NV. , Vo are held in the hold circuit 7, and the values are output to the DC output voltage command value generation circuit 8. At the same time, the start command is output to the DC output voltage command value generation circuit 8, and the DC output voltage command value generation circuit 8 outputs the start command to the hold circuit 7.
DC output voltage V before starting the PWM converter device from
Load that V. is the initial value, and then gradually increases the voltage over time, and finally the PWM converter device C
Change it to the final target output voltage command value of 0NV.

In this way, the DC output voltage command value of the PWM converter device is set to the DC output voltage V before startup. is the initial value, and by gradually increasing the command value, at startup, the value VD detected by the second voltage detector VD2,
The output VR of the DC output voltage command value generation circuit 8 becomes equal, the output of the first compensation circuit 2 becomes zero, and the output IR of the multiplication circuit 3 also becomes zero.

Therefore, when starting up the PWM converter C0NV, the AC input current command, value ■3, starts from zero, and then the output ■8 of the DC output voltage generation circuit 8 gradually increases, and at the same time, the first compensation circuit 2 and the multiplication circuit The output IR of No. 3 also rises gradually, and increases smoothly from the state where the AC input current of the PWM converter device C0NV is zero.

As explained above, when starting up the PWM converter device, by setting the DC output voltage command value to a pattern in which the DC output voltage before startup is the initial value, excessive AC input current can be prevented from flowing, and the GTO thyristor and diode can be This can prevent damage to the circuit and operation of the overcurrent detection circuit.

The same thing can be said when the GTO thyristors T1 to T4 in FIG. 1 are constructed of transistors.

FIG. 2 shows a circuit diagram of another embodiment of the invention.

FIG. 2 shows the hold circuit 7 in the block diagram of FIG.
is omitted, and the initial value of the DC output voltage command value generation circuit 8 is P.
It is fixed at the peak value of the AC input voltage of the WM converter device 1cONV, that is, 2XV.

Since the filter capacitor CO is connected to the output side of the PWM converter device 1CONV, it is charged to the peak value of the AC input voltage before starting. When the fluctuations in the AC input voltage are small, the DC voltage is detected and held in the hold circuit, and the initial value can be set to the peak value of the AC input voltage without having to calculate the initial value of the DC output voltage command value. By fixing it, you can prevent overcurrent during startup.

(Effects of the Invention) Thus, according to the present invention, it is possible to prevent excessive current from flowing at the time of starting up the PWM converter device, prevent damage to the GTO thyristor, diode, etc. in the AC to DC conversion means, and also prevent the PWM converter from flowing smoothly. It will greatly contribute to this field because it can be started up in a number of ways.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a further embodiment of the present invention, and FIG. 3 is an explanatory diagram of a conventional example. PS...AC power supply TR...Transformer...Reactor C0NV...PWM converter device -1~T4・GTO thyristor D1~D4...Diode VDl, V[)2...Voltage detection Device GO...Capacitor CT1...Current transformer■,...DC voltage detection value■,...AC voltage detection value■R...DC output voltage command value IR...AC input current command value ■ ... Initial value of DC output voltage command value 2.4 ... Compensation circuit 3 ... Multiplication circuit 5 ... Modulation wave generation circuit 6 ... Gate amplifier circuit 7 ... Hold circuit 8 ...・DC output voltage command value generation circuit.

Claims (1)

[Claims] 1. In a PWM converter device that performs AC/DC reversible power conversion means using a high frequency pulse width modulation method, there is provided a detector for detecting a DC output voltage, a hold circuit for holding the value, and a hold circuit for holding the value. A starting circuit for a PWM converter device, comprising: a circuit for generating a pattern voltage of a time function having a value set as an initial value, and giving the output thereof as a DC output voltage command at the time of starting the PWM converter device. 2. The PWM converter according to claim 1, which has a circuit that generates a pattern voltage in which the initial value of the pattern voltage of the time function is fixed to the peak value (√2V_s) of the AC input voltage (V_s) of the PWM converter device. Device startup circuit.