JP2003111278A - Controllable series compensating device and energy absorption method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thyristor-controlled series capacitor (TCSC) that prevents the occurrence of an overvoltage in removing system errors and can safely be operated. SOLUTION: In the thyristor-controlled series capacitor (TCSC) wherein a series circuit composed of a reactor 5 and a reverse parallel thyristor 6 is connected in parallel to a series capacitor 4 inserted in a transmission line, there are provided a means 8 for absorbing energy accumulated in the reactor and a second switching means 9. When the full continuity of the thyristor 6 is completed, or when the control of the TCSC is stopped, the switching means 9 is turned on for a short time to rapidly absorb the energy accumulated in the reactor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a controllable series compensator commonly referred to as a thyristor-controlled series compensator or a capacitor (TCSC), and more particularly to a controllable series compensator suitable for preventing overvoltage during system fault elimination and for stable operation. The present invention relates to a compensator and its energy absorption method.

[0002]

2. Description of the Related Art In order to improve power transmission stability, series capacitor compensation is mainly applied in Europe and the United States where long-distance power transmission is performed. Since the series capacitor cancels the impedance of the transmission line, it is apparently short. However, if the degree of compensation by the series capacitor is increased, that is, the impedance of the series capacitor is increased, the electrical resonance point of the power system approaches the mechanical mechanical vibration frequency of the generator, and the shaft torsional vibration (SSR: Sub-synchronous Resonance) is generated. ) Cause problems. As a countermeasure, a thyristor-controlled series compensator or capacitor (TCSC: Thyristor Controlled Series Co
A controllable series compensator known as mpensator) has been developed and is being applied to actual systems. The TCSC is configured by connecting a series circuit of a bidirectional current switch represented by an antiparallel thyristor and a reactor in parallel to a series capacitor. By controlling this thyristor-controlled series reactor, the capacitance of the capacitor can be changed equivalently, so that no resonance point is created.
It is said to be one of the reasons why it does not occur.

Regarding such a controllable series compensator, JP-A-7-255129 and JP-A-9-746 disclose.
No. 82 and Japanese Patent Laid-Open No. 2001-16780.

[0004]

However, when the thyristor is fully turned on in order to protect the TCSC from overvoltage in the event of a system failure, the energy stored in the reactor when the system failure is removed and the full conduction is stopped will result in a series capacitor. Is charged to generate overvoltage. Further, even when the control of the TCSC is stopped from its control state, the energy similarly stored in the reactor is charged in the series capacitor to generate an overvoltage. If this overvoltage is high, stable operation of the TCSC cannot be performed due to overvoltage protection regardless of whether the failure is eliminated or not.

An object of the present invention is to insert a series capacitor inserted in an AC transmission line for series compensation, and a series circuit of switching means such as a reactor and a thyristor connected in parallel to the capacitor for variably controlling the capacity of the series capacitor. In a controllable series compensator equipped with a controllable series compensator, a controllable series compensator that absorbs an overvoltage when a system fault is removed or when the control of the controllable series compensator is stopped and can be operated stably after the fault is removed, and an energy absorption method thereof It is to be.

[0006]

The first feature of the present invention is to detect the stop of full conduction of the switching means in series with the reactor and to connect the energy absorbing means in parallel with the reactor.

A second feature of the present invention is to detect the stop of control of the switching means in series with the reactor and to connect the energy absorbing means in parallel with the reactor.

The invention is also characterized in that the energy absorbing means is disconnected after the scheduled time.

[0009]

FIG. 1 is an electric circuit and control block diagram of a controllable series compensator according to an embodiment of the present invention. 1 is an AC system, 2 is a transmission line, 3 is an AC system, 4 is a series capacitor for compensating the impedance of the transmission line 2, 5
Is a reactor connected in parallel with the series capacitor 4, 6
Is a first switching means for controlling the current flowing through the reactor 5, and has a bidirectional current switching control function. In the figure, a so-called anti-parallel thyristor 6 in which thyristors 61 and 62 are connected in anti-parallel is adopted. The reactor 5 and the antiparallel thyristor 6 constitute a thyristor control reactor, and this thyristor control reactor and the series capacitor 4 are connected in parallel to form a thyristor control series capacitor (or compensator) TCSC, that is, a controllable series compensator. . Reference numeral 7 is an overvoltage protection arrester for the series capacitor 4. 8 is a resistor for energy absorption of the reactor 5, 9 is a second switching means for connecting / disconnecting the resistor 8 for energy absorption to the reactor 5,
Reference numeral 10 is a control circuit of the antiparallel thyristor 6 of the controllable series compensator TCSC.

The operation of this circuit will be described with reference to the time chart shown in FIG. AC system 1 or 3 at time T1
It is assumed that an AC system failure has occurred in. Failure is TCS
Considering the case close to C, a large fault current flows through TCSC, and an overvoltage occurs in series capacitor 4. This overvoltage is generally protected in cooperation with the firing of the arrester 7 and the antiparallel thyristor 6. When the overvoltage exceeds the protection level of the arrester 7, the arrester 7 first limits the peak of the overvoltage. When a failure is detected at time T2, the full-conduction command FCC of the antiparallel thyristor 6 is generated, and the antiparallel thyristor 6 is all fired from time T2. As a result, the current of the arrester 7 moves to the antiparallel thyristor 6, and the fault current flows through the thyristor control reactors 5 and 6. The fault current disappears at time T3 when the fault is removed. However, in this controllable series compensator, the energy stored in the reactor 5 is equal to the capacity of the series capacitor 4 and the reactor 5.
Continues to flow at the vibration frequency determined by the inductance of. T
Since the CSC circuit always causes a loss when the resistance component is large, the resistance component is generally set to be small and the damping of the oscillating current is poor. Therefore, even after the failure recovery, the full continuity command FCC of the antiparallel thyristor 6 is continued and continues to flow until the end of the continuation period T4. At time T4, when trying to return the antiparallel thyristor 6 from full conduction to normal control, the residual energy stored in the reactor 5 is transferred to the series capacitor 4 and a large overvoltage is generated.

At this time, in the present embodiment, the control circuit 10 generates a closing command BPC for the second switching means 9 and turns on the switch 9, thereby connecting the energy absorbing resistor 8 in parallel with the reactor 5. To do. As a result, the overvoltage is rapidly absorbed, and the second switching means 9 is shut off at time T5, which is after the scheduled time for sufficient absorption. Normal TCSC control is performed at time T5 after the scheduled time.
Or at the time T4 in parallel with the ON operation of the second switching means 9. Therefore, it is possible to suppress the occurrence of an overvoltage of the TCSC when the normal TCSC control is started from the full conduction of the anti-parallel thyristor after the failure is removed, and a quick and stable restart operation of the TCSC can be obtained after the failure is removed. The series of operations shown in the time chart of FIG. 2 are arithmetically processed in the control circuit 10 to generate and execute a command.

FIG. 3 is a circuit diagram of an embodiment of the second switching means 9. In order to connect the resistor 8 for absorbing energy to the reactor 5 and disconnect it again at time T5, the switch 9 is connected by the antiparallel connection of the thyristors 91 and 92.
Are configured. The reason why the semiconductor switch element composed of the thyristors 91 and 92 is used is that it needs to be turned on at high speed. If the input is delayed, TCSC
Overvoltage appears. On the other hand, after achieving the suppression of the overvoltage, high-speed disconnection is necessary in order to quickly return to the normal TCSC control operation in which the loss due to the resistor 8 does not occur.

FIG. 4 is a circuit diagram of another embodiment of the second switching means 9. An example in which a resistor R8 for absorbing energy is connected to the reactor 5 and is disconnected again at time T5 so that the reactor 5 is constituted by a high speed circuit breaker or a high speed switch 93 is shown. By adopting a high-speed circuit breaker and a high-speed switch,
The energy absorbing resistor 8 can be turned on and off at a high speed without cost compared with.

FIG. 5 shows an ON / OFF command generating circuit for the second switching means 9. The circuit has a simple configuration including only the timer circuit 101. The input of the timer circuit 101 is a full conduction command FCC (see FIG. 2) of the anti-parallel thyristor 6 of the TCSC made by the control circuit 10, and the timer circuit 101 is set at the timing T4 of its end, and the reactor 5 and the energy are set. At the time determined by the time constant of the circuit composed of the absorbing resistor 8, the timer is reset at time T5 after a timer setting time with a certain margin. As a result, the closing command BPC of the second switching means 9 becomes as shown in FIG.

According to the above embodiment, the energy of the reactor 5 accumulated by the full conduction of the anti-parallel thyristor 6 of the TCSC can be absorbed at the high speed at the time of removing the system fault, so that the overvoltage generation of the TCSC after the fault is removed. The TCSC can be restarted quickly and stably, and the recovery from the failure can be accelerated.

Also, when the control of the TCSC is stopped from its operation control state, the energy stored in the reactor 5 is transferred to the series capacitor 4 and overvoltage is generated.
Here, stopping the control means that the antiparallel thyristor 6 in the TCSC stops firing and the current stops flowing in the reactor 5. Therefore, also in this case, it is preferable that the resistor 8 absorb the energy of the reactor 5 when the control of the TCSC is stopped.

FIG. 6 is a time chart for explaining the energy absorption operation after the control of the controllable series compensator TCSC according to this embodiment is stopped. The switch 9 closing command BPC is turned off at a time T5 after a time T4 'when the start / stop command of the TCSC is switched to the stop, and a time after allowing time for energy absorption. In this case, the command value creating circuit for turning on / off the switch 9 is the same as that in FIG. 5, and the timer setting may be left unchanged. However, the only difference is that a TCSC start / stop command is input as an input signal instead of the full-conduction command FCC.

According to this embodiment, the energy stored in the reactor 5 can be absorbed at a high speed when the control of the TCSC is stopped, overvoltage can be prevented, and the TCSC can be operated stably.

[0019]

According to the present invention, the energy stored in the reactor in the controllable series compensator can be absorbed at a high speed at the time of eliminating the system fault to prevent the overvoltage from occurring, the stable operation can be performed, and the recovery from the fault can be performed. It can be hastened.

Further, if the stored energy of the reactor is absorbed even when the control of the controllable series compensator is stopped, overvoltage can be similarly prevented and stable operation can be achieved.

[Brief description of drawings]

FIG. 1 is an electric circuit and control block diagram of a controllable series compensator according to an embodiment of the present invention.

FIG. 2 is a time chart of energy absorption operation after a system failure according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of an embodiment of second switching means.

FIG. 4 is a circuit diagram of another embodiment of the second switching means.

FIG. 5 is a circuit diagram of an on / off command generating circuit for the second switching means according to an embodiment of the present invention.

FIG. 6 is a time chart illustrating an energy absorption operation when control is stopped in the controllable series compensation device according to another embodiment of the present invention.

[Explanation of symbols]

1 ... AC system, 2 ... Transmission line, 3 ... AC system, 4 ... Series capacitor, 5 ... Reactor, 6 ... First switching means (anti-parallel thyristor), 61, 62 ... Thyristor, 7
... overvoltage protection arrester, 8 ... energy absorbing resistor, 9 ... second switching means, 91,92 ... thyristor (semiconductor switch element), 93 ... high speed circuit breaker (high speed switch), 10 ... controllable series compensation Device control circuit,
101 ... Timer circuit.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Teru Kikuchi             7-1-1, Omika-cho, Hitachi-shi, Ibaraki Prefecture             Inside the Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Yasuo Morioka             3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture             Kansai Electric Power Co., Inc. F term (reference) 5G066 AD01 AD11 FA01 FB08 FC11

Claims (6)

[Claims] 1. A series capacitor inserted in an AC transmission line for series compensation, and a reactor connected in parallel to the capacitor for variably controlling the capacity of the series capacitor.
In the controllable series compensator including the series circuit of the switching means, the series circuit of the energy absorbing means and the second switching means connected in parallel to the reactor, and when the first conduction of the first switching means is completed. A controllable series compensator, comprising control means for turning on the second switching means. 2. A series capacitor inserted in an AC transmission line for series compensation, and a reactor connected in parallel to the capacitor for variably controlling the capacity of the series capacitor.
In the controllable series compensator including the series circuit of the switching means, the series circuit of the energy absorbing means and the second switching means connected in parallel to the reactor, and the control circuit when the control of the first switching means is stopped. A controllable series compensator, comprising control means for turning on the second switching means. 3. The controllable series compensator according to claim 1, further comprising means for turning off the second switching means which has been turned on after a predetermined time. 4. The semiconductor switch according to claim 1, wherein the first switching means comprises an anti-parallel thyristor, and the second switching means is a high-speed circuit breaker or a bidirectional current controllable. A controllable series compensator including an element. 5. A controllable series compensation comprising a series capacitor inserted in an AC transmission line for series compensation, and a series circuit of a reactor and a switching means connected in parallel to the series capacitor for variably controlling the capacity of the series capacitor. In the control method of the apparatus, a step of detecting a full conduction stop or a control stop of the switching means, a step of connecting energy absorbing means in parallel to the reactor at the time of detecting the stop, and a step of disconnecting the energy absorbing means after a scheduled time. An energy absorbing method for a controllable series compensator, comprising: 6. A thyristor-controlled series compensator configured by connecting a reactor and an anti-parallel thyristor for controlling a current flowing in the reactor in series to a series capacitor inserted in a transmission line. , Means for absorbing energy stored in the reactor,
The output of this timer means is provided with means for switching the absorbing means, means for detecting the end of full conduction and / or control end of the antiparallel thyristor, and timer means set by the output of this detecting means and reset after a predetermined time. The thyristor-controlled series compensating device, wherein the switching means is turned on to connect the energy absorbing means to the reactor.