CN201118224Y - A short-circuit fault current limiter for power system - Google Patents

Abstract

The utility model discloses a short-circuit fault current limiter of a power system, which comprises a bridge composed of electronic switches ES1, ES2, ES3 and ES4, a DC current-limiting reactor L1, a parallel inductor L2 and a DC bias power supply Eb; the electronic switch One end of ES1, one end of electronic switch ES3 and one end of DC current limiting reactor L1 are connected together; the other end of DC current limiting reactor L1 is connected together with the negative pole of DC bias power supply Eb; one end of electronic switch ES2, electronic One end of the switch ES4 is connected with the positive pole of the DC bias power supply Eb; one end of the parallel inductor L2, the other end of the electronic switch ES1, and the other end of the electronic switch ES2 are connected together, which is an outlet terminal of the current limiter access line ; The other end of the parallel inductance L2 is connected with the other end of the electronic switch ES3 and the other end of the electronic switch ES4, which is another outlet terminal of the current limiter access line. The device is applied to an AC voltage power supply system, which can not only limit the rising rate of the short-circuit current at the initial stage of a short-circuit fault, but also limit the steady-state value of the short-circuit current after the short-circuit fault occurs, and has low cost.

Description

A short-circuit fault current limiter for power system

technical field

The utility model relates to a power system short-circuit fault current limiter applied to an AC voltage power supply system, which is a device for limiting the short-circuit fault current and its rising rate, and belongs to the technical field of AC flexible power transmission technology.

Background technique

With the continuous expansion of power system scale and capacity, the level of short-circuit current increases rapidly. When the level of short-circuit current exceeds the breaking capacity of circuit breakers, short-circuit faults may cause serious damage to major power equipment such as transformers, high-voltage switchgear, and power cables. damage, causing system instability, or even system paralysis. The short-circuit fault current limiter, after detecting the occurrence of a short-circuit fault, quickly changes the impedance parameters of the fault line to limit the short-circuit current to an allowable level to protect power equipment. It has become one of the key components of the flexible AC transmission system.

The dotted line in Figure 1 is a short-circuit current limiter based on a bidirectional switch and a rectifier bridge switching method. In the figure, L1 is a DC inductor, and four bidirectional or unidirectional electronic switches such as ES1-ES4 form a bridge. , through control, the bridge can work either in the rectification state or in two bidirectional switching states, so as to ensure that L1 can limit the steady-state value of the AC short-circuit current after a short-circuit fault occurs; Eb is the DC bias voltage, used To compensate the diode voltage drop, to ensure that the current in the inductor L1 is always greater than the peak value of the load rated current, so as to ensure that the grid voltage has no distortion. Us is the power supply voltage, X1 is the line impedance, R1 is the load impedance, and CB is the circuit breaker. The current limiter can automatically limit the rising speed of the short-circuit current at the initial stage of the short-circuit fault; after the short-circuit fault is detected, the control rectifier bridge is switched to two bidirectional electronic switches, and the inductor L1 is connected in series with the AC circuit to limit the short-circuit current. Steady-state value, and in general, electronic switches use thyristor components, and the bridge circuit switches at the zero-crossing point of the current. Switching will not cause overvoltage and additional oscillation, and the short-circuit current after limitation has no distortion and no electromagnetic interference. In order to meet the selectivity requirements of power system relay protection devices, after a short-circuit fault occurs, the short-circuit current needs to be maintained at 5 to 10 times the rated load current for a period of time. For this reason, in the current limiter shown in Figure 1, the short-circuit current must pass through the bridge circuit, so the rated current value of the bridge circuit is very large, resulting in high cost of the current limiter.

Utility model content

The purpose of the utility model is to overcome the defects of the prior art and provide a short-circuit fault current limiter for power systems. By adding parallel inductors, the current rating of the bridge circuit and L1 is reduced, thereby reducing the cost of the entire current limiter.

The utility model is a short-circuit fault current limiter of a power system, which adopts a bidirectional and unidirectional controllable electronic switch composed of a thyristor and a diode to form a bridge, and an inductor is connected in parallel to the AC end of the bridge. When the power system is normal, The control bridge works in the state of uncontrolled rectification. Since the inductor L1 bears DC voltage, the voltage at both ends of it is close to zero, and the voltage at both ends of the parallel inductor is also close to zero. Once a short circuit fault occurs, the control bridge immediately works in two bidirectional switching states , after the peripheral inductance and L1 are equivalently connected in parallel, they are connected in series to the AC power supply system to limit the steady-state value of the short-circuit current. The parallel inductance of the peripherals bears most of the short-circuit current, thereby reducing the voltage rating of the bridge and reducing the cost of the current limiter.

The utility model relates to a short-circuit fault current limiter of a power system, comprising a bridge composed of electronic switches ES1, ES2, ES3 and ES4, a DC current-limiting reactor L1, a parallel inductor L2 and a DC bias power supply Eb; wherein, the electronic switch One end of ES1, one end of electronic switch ES3 and one end of DC current limiting reactor L1 are connected together; the other end of DC current limiting reactor L1 is connected together with the negative pole of DC bias power supply Eb; one end of electronic switch ES2, electronic One end of the switch ES4 is connected with the positive pole of the DC bias power supply Eb; one end of the parallel inductor L2, the other end of the electronic switch ES1, and the other end of the electronic switch ES2 are connected together, which is an outlet terminal of the current limiter access line ; The other end of the parallel inductance L2 is connected with the other end of the electronic switch ES3 and the other end of the electronic switch ES4, which is another outlet terminal of the current limiter access line. When in use, the current limiter is connected in series between the circuit breaker of the power line and the load through two outlet terminals.

The electronic switches ES1, ES2, ES3, and ES4 are two-way controllable electronic switches composed of two thyristors, which is a realization scheme.

Taking electronic switches ES1, ES4 (or ES2, ES3) as bidirectional electronic switches composed of thyristors and diodes, and ES2, ES3 (ES1, ES4) as thyristors is a realization scheme.

Reactor L1 can be superconducting or conventional, and superconducting reactors are more suitable for the method and device of the present invention. According to economic requirements, it is best to use conventional inductors for L2.

The utility model is applied to an AC voltage power supply system, which can not only limit the rising rate of the short-circuit current at the initial stage of a short-circuit fault, but also limit the steady-state value of the short-circuit current after the short-circuit fault occurs, and has low cost.

Description of drawings

Fig. 1 is the current limiting device circuit diagram of prior art;

Fig. 2 is the main circuit schematic diagram of a kind of power system short-circuit fault current limiter of the utility model;

Fig. 3 is the main circuit schematic diagram of a kind of power system short-circuit fault current limiter of the present utility model (bidirectional electronic switch ES1, ES2, ES3 and ES4 are all formed by two thyristor SCR antiparallel connections);

Fig. 4 is a schematic diagram of the main circuit of a power system short-circuit fault current limiter of the present utility model (electronic switches ES1 and ES4 are bidirectional electronic switches composed of thyristors and diodes antiparallel, ES2 and ES3 are unidirectional electronic switches composed of thyristors );

Detailed ways

The utility model is described in further detail below with reference to accompanying drawing and embodiment.

Embodiment 1, as shown in Figure 3, includes a bridge composed of electronic switches ES1, ES2, ES3 and ES4, a DC current limiting reactor L1, a parallel inductor L2 and a DC bias power supply Eb; wherein, one end of the electronic switch ES1 1. One end of the electronic switch ES3 is connected together with one end of the DC current limiting reactor L1; the other end of the DC current limiting reactor L1 is connected together with the negative pole of the DC bias power supply Eb; one end of the electronic switch ES2, one end of the electronic switch ES4 One end is connected to the positive pole of the DC bias power supply Eb; one end of the parallel inductor L2, the other end of the electronic switch ES1, and the other end of the electronic switch ES2 are connected together, which is an outgoing terminal of the current limiter access line; the parallel inductor The other end of L2 is connected together with the other end of the electronic switch ES3 and the other end of the electronic switch ES4, which is another outlet terminal of the current limiter access line.

The bi-directional electronic switches ES1, ES2, ES3 and ES4 are all composed of two thyristors SCR connected in antiparallel. When the system is normal, control thyristors T1, T2, T3, and T4 to be in the normally-on state, and control T5, T6, T7, and T8 to be in the off state, then the bridge composed of switching devices works in an uncontrolled rectification state. In the stable state after the inductor L1 is magnetized, since the bias power supply Eb compensates the on-state voltage drop of the switch tube, the slight current in L1 is greater than the peak value of the rated load current, and the voltage between the two outlet terminals A and B of the current limiter is zero, the voltage across the parallel inductor L2 is zero, and the existence of the current limiter has no effect on the system. When a short-circuit fault occurs, the power supply voltage is added to the DC inductor L1 through the rectifier bridge, causing the current of L1 to increase. Since L1 is located on the DC side of the bridge, the voltage passing through the rectifier bridge has a single polarity. If the bridge has been working at In the rectification state, the current of L1 will continue to increase; at the same time, the power supply voltage is applied to both ends of the parallel inductor L2, and an alternating current is generated in L2. In this circuit, when the L1 current is greater than the set value, a trigger signal can be added to T1, T5, T4, T8 (or T2, T6, T3, T7) to ensure its conduction, remove T2, T6, T3, The trigger signal of T7 (or T1, T5, T4, T8) ensures that these tubes are turned off after the current crosses zero, that is, the control bridge is switched to a bidirectional switch state, and L1 and L2 are connected in parallel and connected in series to the AC path. To limit the steady-state value of the short-circuit current. The design of the parameters should ensure that L2 bears most of the current required by the relay protection device, and L1 and the bridge circuit bear a small part of the current, which can significantly reduce the cost of the current limiter. If it is guaranteed that when the positive half cycle of the power supply is short-circuited, turn on T1, T5, T4, T8 and turn off T2, T6, T3, T7; when the negative half cycle of the power supply is short-circuited, turn on T2, T6, T3, T7 and turn off T1, T5 , T4, T8, the current at both ends of the inductor L1 can be reversed in the next half cycle, and the inductance of L1 can be much smaller (compared with the latter scheme).

Embodiment 2, as shown in FIG. 4 , is basically the same as Embodiment 1, except that the electronic switches ES1 and ES4 are bidirectional electronic switches composed of thyristors and diodes, and ES2 and ES3 are thyristors. Under normal circumstances, control T2 and T3 to turn on, and T1 and T4 to turn off, then D1, D2, T2 and T3 form an uncontrolled rectifier bridge. After the short-circuit fault occurs, turn off the T2 and T3 tubes and control the T1 and T4 tubes to be in the normally-on state, then the bridge circuit is converted into two bidirectional switches, and the inductors L1 and L2 are connected in parallel and connected in series to the AC circuit to limit the short-circuit current. steady state value. After a short circuit occurs in the negative half cycle of the power supply voltage, the L1 current will still bear the upper positive and lower negative voltages in the next half cycle, so the L1 current may start from the peak value of the load current rating and continue to increase within one cycle, so the inductance of L1 The value will be much larger than the solution shown in Figure 3, but the circuit structure is simpler.

Claims (3)

1, a kind of short-circuit fault of power system flow restricter comprises the bridge circuit, direct current current-limiting reactor L1, shunt inductance L2 and the dc bias power Eb that are made up of electronic switch ES1, ES2, ES3 and ES4; It is characterized in that: one of the end of electronic switch ES1, the end of electronic switch ES3 and direct current current-limiting reactor L1 terminates at together; The other end of direct current current-limiting reactor L1 and the negative pole of dc bias power Eb are connected together; The positive pole of the end of electronic switch ES2, the end of electronic switch ES4 and dc bias power Eb is connected together; The other end of the end of shunt inductance L2, the other end of electronic switch ES1, electronic switch ES2 is connected together, and is an outlet terminal of flow restricter line attachment; The other end of the other end of the other end of shunt inductance L2 and electronic switch ES3, electronic switch ES4 is connected together, and is another outlet terminal of flow restricter line attachment.

2, a kind of short-circuit fault of power system flow restricter according to claim 1 is characterized in that: described electronic switch ES1, ES2, ES3, the bidirectional electronic switch of ES4 for being made up of two thyristor reverse parallel connections.

3, a kind of short-circuit fault of power system flow restricter according to claim 1, it is characterized in that: described electronic switch ES1, ES4 or ES2, ES3 bidirectional electronic switch for forming by thyristor and diode inverse parallel, ES2, ES3 or ES1, ES4 are thyristor, and its direction satisfies from the requirement of rectifier bridge to two a bidirectional electronic switch conversion.

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