JPS5851742A - Starter for ac/dc converter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] This invention provides a method for detecting problems caused by transformer saturation when starting an AC/DC converter in which a converter configured with a switch having forced commutation capability is connected to an AC system via a transformer. The present invention relates to a starting device that suppresses overcurrent in a converter.

The AC/DC converter station that connects the DC system and AC system is configured as shown in Figure 1B1. In the figure, (1) is the power transmission line of the DC system, (2)' is the converter connected to the DC system (1), (3) is the transformer connected to the AC side of the converter, (
4) is a switch for connecting the transformer (3) to the AC system (5). The converter (2) is a so-called automatic converter comprising a switch having forced commutation capability, and is configured as shown in FIG. 2, for example.

In FIG. 2, (P) (to) is a DC terminal, which is connected to the DC power transmission line (1). So is the smoothing capacitor connected between the lines of the DC terminal, C201) C202) C2
0B) C204 (205) (106) C main thyristor, (221) (222) (228 P224) (2ss
)(2zg) is the auxiliary thyristor, (211)(2!1
2) (21B (214) (+16) (21B) is a freewheel diode, (281B (28)
B) is a commutation reactor, (241 bar 242) (24B)
is a commutating capacitor. Two main thyristors are connected in series, and an AC output terminal 0° is led out from the intermediate point. The AC output terminal is connected to a transformer (3).

The operation of the automatic converter of FIG. 2 is well known.

Conventionally, the method for starting such an automatic conversion device is to charge a smoothing capacitor (E) to a predetermined value using a separate power source (not shown), and then apply a conduction signal to the thyristors in a predetermined order. A method was taken. When a conduction signal is given to the thyristor, the AC output terminal ((J)
, (V), W) This generates an AC voltage proportional to the DC voltage value of the smoothing capacitor, but this causes a large excitation current called inrush current to flow in the output transformer (3). It is known that this exciting current is
Since it flows through the main thyristor of the converter, the current carrying capacity of the converter increases and the device becomes larger. For you,
It is necessary to suppress inrush current at startup as much as possible. Inrush current increases as the voltage applied to the transformer increases, so in conventional automatic converters that have an output transformer on the AC output side, in order to suppress the inrush current of the output transformer at startup, The starting method is to start with a low DC voltage, first keep the voltage applied to the transformer low, and then gradually increase the voltage.However, as shown in Figure 1. For automatic converters connected to a DC power line, the voltage of the DC power line directly becomes the DC voltage of the converter, so the conventional startup method cannot be used. The drawback was that excessive current flowed through the converter arm.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by supplying the inrush current of the output transformer from the AC system side, the automatic It is an object of the present invention to provide a startup method that can suppress the current flowing through the converter and reduce the current capacity of the converter even when starting the converter of the formula.

An embodiment of the invention of ξ will be described below with reference to the drawings. In Fig. 8, Zeng indicates an AC system. (2) is a start signal generator that gives a closing command to the breaker (4) tomorrow.

(2) is a voltage detector that detects the voltage of the AC system, Iwa is a phase detector that detects the phase of that voltage, and Trout is a voltage detector that compares the voltage phase on the grid side with the converter gate pulse phase and detects the deviation. (2) is a filter that converts the output signal of the phase difference detector into a DC voltage; (2) is a voltage frequency converter that converts the output voltage of the filter into a frequency;
2) is a gate pulse generator that divides the output of (2) and generates gate pulses for each thyristor of the converter;
) is a phase detector that detects the phase of the gate pulse.

94. @, tlj, tlj.

The loop consisting of (2) constitutes a phase-locked loop. A phase-locked circuit is a circuit that generates a pulse synchronized with the phase of an input pulse. For example, in electronic science? There is something described in "Basic Theory of PLL", November 8th issue. (2) is two phase detectors (2) 1w
A phase-scattered type timer that outputs an output when the outputs of (4) match is a timer that generates an output after a certain period of time from the input signal in (4). (To) is an AND logic circuit that outputs an output when both the output of ■ and the output of 4 are output, (To) is (
It is an AND logic circuit that applies the gate pulse generated from (2) to each sirisk only when the output from (2) is produced, and cuts off the gate pulse when there is no output from (to).

Next, the operation will be explained. Until the start signal is given, the voltage phase of the AC system is detected by @-, and this and (
The gate pulse 1 phase detected in e) is compared with -.

If the phase detected in (2) lags behind the phase detected in step 4, the output of (c) will become thicker, and as a result, the DC output voltage of (2) will also become larger, causing ring oscillation. Frequency increases. As a result, the frequency of the gate pulse generated by the powder also increases, and the gate pulse phase detected in (2) advances. Conversely, when the phase detected in (2) is ahead of the phase detected in (4), the output of the shaft becomes smaller, and as a result, the DC output voltage in (2) also becomes smaller, and the oscillation frequency (to) decreases. As a result, the frequency of the gate pulses generated in the positive phase decreases, and the gate pulse phase detected in the positive phase is delayed. In this way, due to the function of the phase synchronization circuit of 94 (to) @@, the detection phase of (2) and (2) are always
) is determined to match the detection phase. As a result, if a gate pulse is given to each f risk in (2), the gate pulse phase will be synchronized so that the voltage in the same phase as the ring is generated in the system side winding in (3). It is being However, the gate pulse is blocked due to CI and the other signals are not coming. In this state, when the closing commands (2) to (4) are issued, startup is performed as shown in FIG. 4. In Fig. 4, time tl indicates the time point 1 when the closing command was issued from (b) to (4), and in response to this closing command, the timer
Generate an output at time t3 after a predetermined time (To) and give it to 6p.

01) is given this signal and the output of Kan, but @
:Yo, the phase synchronization circuit in the first half is working properly, and (a) and (
It is checked whether the phases of (to) and °C match, and if they match, an output is output. In FIG. 8, it is assumed that synchronization has been completed at time t2.

Therefore, at time t3, since both inputs of (b) are applied A, 3I) gives an output to (2) at time t3 and deblocks the gate pulse. the result,
After time t3, the gate pulses generated by the transistors are applied as they are to each thyristor (2). For example, the gate pulse of the U-phase thyristor (201) in the fJit diagram is as shown in the same figure. It will be done. As a result, the line voltage between Uv in (3) is as shown in the same figure. The excitation current flows largely when the voltage is applied to (3), but then decreases and eventually reaches a steady value. This initial excessive current (so-called rush current) flows from the system ■ via the breaker (4), and flows into the converter (2).
is blocked, so only the charging current of the smoothing capacitor flows. This current flows through the freewheel V diode. At t3, when the gate pulse is applied to the iris, the excitation current (3) has reached a steady value, so there is no need to supply an excessive excitation current from the converter.

In the above embodiment, the converter (2) is a 6-phase converter, but it may be a multi-M converter that adds the outputs of a plurality of 6-phase converters using an output converter. . In this case, it goes without saying that the multiplexing transformer corresponds to the output transformer (3) of the present invention.

In addition, in the embodiment shown in FIG. 8, the timer (4) is configured to determine the start time, but it is also possible to give the operation command to C (6) from another circuit instead of the evening/immediate time. This is good. In this way, after the breaker (4) is turned on, until an operation command is received, the converter will be in a so-called timing state, in which it will not operate, but it will be in a broaching state where it can be activated immediately when an operation command is received. can.

As described above, according to the present invention, there is no need to supply inrush current to the converter transformer from the converter side, so overcurrent at the time of starting the converter can be avoided. Another advantage of the present invention is that since the smoothing capacitor is charged from the AC system via the output transformer, there is no need to charge the smoothing capacitor from another power source before starting up.
It has the effect of starting up independently even when there is no other power source.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of an AC/DC conversion station, and Fig. 2 is a block diagram showing an example of an AC/DC conversion station.
FIG. 8 is a configuration block diagram showing an example of starting the AC/DC converting device according to the present invention. FIG. 4 is a time chart at startup by the starting device of the present invention. It is. In the figure, (1) is a DC system, (2) is an automatic converter, (3) is a transformer, (4) is a switch, (5) one wheel is an AC system, and (C) is a starting signal generator. , the wire is a voltage detector, (
2) (2) is a phase detector, (2) is a phase photodetector, (2
) is a filter, (e) is a voltage frequency converter, (support) is a gate noculus generator, (4) is a phase-scattered field type, (to) is a timer, and (01) @ is an AND logic circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts @ Agent Shin Akino - Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] For starting an automatic conversion device that is installed between a transformer connected to one AC system via a breaker and a DC transmission line and performs power conversion between DC power and AC power, a phase detector that detects a voltage phase; and a phase-scattered field type that detects that a phase difference between the detected phase of the phase detector and the phase of a gate pulse that controls ignition of the conversion device is less than a certain value. , a timer circuit that outputs an output after a predetermined period of time has elapsed since the generation of the closing signal for the breaker, and the timer circuit and the phase-integrator.