JP2000350368A - Series compensating device and switching element controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a switching element to operate properly at the time of a system failure and the elimination of the failure. SOLUTION: The phase difference between a synchronizing pulse signal Sn that is synchronized with the current of a system and a reference pulse signal Ss is detected by a phase difference detecting circuit 44. This phase difference Δθ is amplified by a calculating and amplifying circuit 46 to obtain a control voltage Ec and to generate a pulse signal of an oscillating frequency in proportion to the control voltage Ec by a voltage controlling and oscillating circuit 56. The frequency of this pulse signal is divided by a frequency divider circuit 58 to generate a reference pulse signal Ss. Based on this signal, a firing pulse signal for igniting each thyristor is generated. If a failure occurred in the system, a pulse signal is generated of the oscillating frequency based on the control voltage Ec' that has been stored in a phase memory circuit 54 prior to the occurrence of the failure. Then, the frequency of this pulse signal is divided by the frequency divider circuit 58 to generate the reference pulse signal Ss.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a series compensator and a switching element controller, and more particularly, to controlling the operation of a switching element connected in parallel with an AC reactor to a series capacitor inserted in an AC transmission line. The present invention relates to a series compensator and a switching element controller suitable for the present invention.

[0002]

2. Description of the Related Art In an AC system composed of an AC transmission line, a series capacitor inserted in series with the AC transmission line is considered to be effective in improving the steady state stability and transient stability of the AC transmission line. The system has been adopted. This system is widely used in Northern Europe, North and South America, where many long-distance transmission lines are used.

When the series compensation system is applied to an AC transmission line, if the amount of compensation is increased in order to increase the compensation effect, the electric power generated by L (inductance) of the transmission line and generator and C (capacity) of the series compensator is increased. The typical resonance frequency approaches the commercial frequency, and the torsion of the generator (SSR) becomes a problem. As a countermeasure, a thyristor controlled series capacitor (TCS) that changes the capacity of the series capacitor with a thyristor
C) was developed mainly by the United States Electric Power Research Institute (EPRI), and is being tested in the field. If the overseas operation results from this demonstration test and the like are accumulated, there is a possibility that thyristor-controlled series capacitors will be used for voltage stability and stability improvement in the Japanese power system where voltage stability is a problem under heavy load Is big.

[0004]

In order to make full use of the effect of the thyristor control series capacitor, it is necessary to stabilize the operation at the time of system failure and at the time of system failure elimination. Therefore, in the past, in the event of a system failure, an arrester or
It is considered that the thyristor is protected by a terminal short circuit due to full conduction. However, even after the fault of the system is eliminated, the fault current decreases, and even after the protection operation ends, it is difficult for the thyris to immediately return to the original operation. This depends on the type of failure and whether the point of failure is near or far from the thyristor control series capacitor, but if a DC component is superimposed on the fault current or a harmonic current is superimposed, the firing phase of the thyristor is detected. This is because it is difficult to fire the thyristor with an appropriate phase. If the thyristor that constitutes the thyristor control series capacitor is not operated properly when a system fault occurs and when the fault is eliminated, the operation of the thyristor will adversely affect the system and prolong the recovery from the fault. Become.

An object of the present invention is to provide a series compensator and a switching element controller capable of appropriately performing the operation of a switching element at the time of a system fault and at the time of clearing the fault.

[0006]

In order to achieve the above object, the present invention provides a series capacitor inserted in series in an AC transmission line, an AC reactor connected in parallel to the series capacitor, and an AC reactor connected to the series capacitor. A switching element connected in series to control a phase of a current flowing through the AC reactor in response to a firing pulse signal; an electric signal detecting unit detecting an electric signal of the AC transmission line; a command value and the electric signal detection Command value generation means for calculating a firing phase angle with respect to the switching element according to a deviation from a detection value of the means and generating a control angle command value according to the calculation result;
Failure detection means for detecting a failure in an AC system based on the electric signal of the AC transmission line, and synchronization pulse signal generation means for generating a synchronization pulse signal synchronized with the electric signal in response to the electric signal of the AC transmission line A control voltage generating means for generating a control voltage corresponding to a phase difference between the reference pulse signal and the synchronization pulse signal; and a fault in the AC system by the fault detecting means among the control voltages generated by the control voltage generating means. Control voltage storage means for storing a control voltage generated before detection, and selecting a control voltage stored in the control voltage storage means in response to a failure detection output of the failure detection means; Control voltage selection means for selecting a control voltage generated by the control voltage generation means; and a pulse signal having an oscillation frequency corresponding to the control voltage selected by the control voltage selection means. , A reference pulse signal generating means for generating a reference pulse signal according to an output pulse signal of the voltage control oscillating means, and a reference pulse signal generating means for generating a reference pulse signal according to a command value generated by the command value generating means. And a pulse phase shifting means for generating an ignition pulse signal by shifting the reference pulse signal and outputting the ignition pulse signal to the switching element.

[0007] In configuring the series compensator,
Instead of the electric signal detection means, a current detection means for detecting the current of the AC transmission line, a voltage detection means for detecting the voltage of the AC transmission line, and an AC based on a detection current of the current detection means and a detection voltage of the voltage detection means. An impedance calculating means for calculating the impedance of the transmission line is provided, and instead of the command value generating means, a firing phase angle for the switching element is calculated according to a deviation between the impedance command value and the calculated value of the impedance calculating means. A command value generating means for generating a command value of the control angle according to the calculation result is provided,
Instead of the reference pulse signal generation means, a reference pulse signal generation means for generating a reference pulse signal by dividing the output pulse signal of the voltage controlled oscillation means may be provided.

Further, the present invention provides an electric signal detecting means for detecting an electric signal of an AC power transmission line, a command value for a firing phase angle for a switching element inserted in the AC power transmission line, and a detection of the electric signal detecting means. Command value generation means for calculating a command value of the control angle in accordance with the calculation result, and failure detection means for detecting a failure of the AC system based on the electric signal of the AC transmission line. Synchronizing pulse signal generating means for generating a synchronizing pulse signal synchronized with the electric signal in response to the electric signal of the AC transmission line, and generating a control voltage corresponding to a phase difference between a reference pulse signal and the synchronizing pulse signal Control voltage generating means, and a control voltage storage for storing a control voltage generated before the failure of the AC system is detected by the failure detecting means among the control voltages generated by the control voltage generating means. And a control voltage selector for selecting a control voltage stored in the control voltage storage means in response to a failure detection output of the failure detection means, and otherwise selecting a control voltage generated by the control voltage generation means. Means, voltage-controlled oscillating means for outputting a pulse signal having an oscillation frequency corresponding to the control voltage selected by the control voltage selecting means, and a reference pulse signal for generating a reference pulse signal according to the output pulse signal of the voltage-controlled oscillating means Generating means for generating a firing pulse signal by shifting a reference pulse signal generated by the reference pulse signal generating means in accordance with a command value generated by the command value generating means, and outputting the firing pulse signal to the switching element And a switching element control device comprising a phase shift means.

In configuring the switching element control device, instead of the electric signal detecting means, a current detecting means for detecting a current of the AC transmission line, a voltage detecting means for detecting a voltage of the AC transmission line, An impedance calculating means for calculating the impedance of the AC transmission line from the detected current of the means and the detected voltage of the voltage detecting means is provided, and instead of the command value generating means, a deviation between the impedance command value and the calculated value of the impedance calculating means is calculated. Calculate the firing phase angle with respect to the switching element in accordance therewith, and provide command value generating means for generating a command value of the control angle in accordance with the calculation result.
Reference pulse signal generation means for generating a reference pulse signal by dividing the output pulse signal of the voltage controlled oscillation means may be provided.

The following elements can be added when configuring each series compensator or switching element controller.

(1) In response to a failure detection output of the failure detection means, an accident occurrence start timer means for instructing the control voltage selection means to switch the selection of the control voltage when a set time has elapsed thereafter. Be prepared.

(2) Elimination of an accident in which the control voltage selection means is instructed to switch the selection of the control voltage when a predetermined time has elapsed after the failure detection means has stopped generating a failure detection output. Post-start timer means is provided.

According to the above-mentioned means, at the time of a system failure, a reference pulse signal is generated based on the control voltage generated before the occurrence of the system failure, and the ignition pulse generated according to the reference pulse signal is generated. Since the signal is provided to the switching element, the operation of the switching element at the time of system failure and at the time of failure elimination can be appropriately performed, and the recovery from a system failure can be accelerated.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a series compensator showing one embodiment of the present invention. In FIG. 1, three-phase (U-phase, V-phase, and W-phase) AC transmission lines 14, 16, and 18 connecting the AC systems 10 and 12 have transmission lines 14, 16, and 18 respectively.
18 impedances (reactors 20u, 20v, 2
To compensate (cancel) 0w, 22u, 22v, and 22w), series capacitors Cu, Cv, and Cw are inserted in series, respectively. AC reactors Lu, Lv, Lw are connected to thyristors Thu, Thx, Th in series capacitors Cu, Cv, Cw, respectively.
v, Thy, Thw, and Thz are connected in parallel. U-phase thyristors Thu, Thx, V-phase thyristors Thv, Thy, W-phase thyristors Thw, Thz
Are connected in antiparallel to each other to form AC reactors Lu, Lv,
Lw and the series capacitors Cu, Cv, and Cw, respectively. Each of the thyristors Thu to Thz is configured as a switching element that controls the phase of a current flowing through each of the reactors Lu, Lv, and Lw in response to a firing pulse signal from the control device 24, and includes series capacitors Cu, Cv, Cw, AC reactor Lu, Lv, L
Together with w, it is configured as a thyristor controlled series capacitor.

The AC transmission lines 14, 16, and 18 detect the electric current of each of the AC transmission lines 14, 16, and 18 as electric signal detecting means for detecting electric signals of the AC transmission lines 14, 16, and 18. AC current detector 2 as current detecting means
6u, 26v, 26w are provided, and AC voltage detectors 28u, 28v, 28 as voltage detecting means for detecting voltages of the AC transmission lines 14, 16, 18 respectively.
w, 28u ', 28v', 28w 'are AC transmission lines 14, 1
6, 18 are connected. And each AC current detector 2
Outputs of 6u to 26w and AC voltage detectors 28u to 28w 'are input to the control device 24, respectively.

As shown in FIG. 2, the control device 24 includes impedance detection circuits 30u, 30v, 30w, a failure detection circuit 32, impedance control circuits 34u, 34v, 3
4w, a switching circuit 36, a synchronization signal detection circuit 38, a synchronization signal creation circuit 40, and a pulse phase shift circuit 42.

The impedance detection circuit 30u is configured as impedance detection means for detecting the impedance of the transmission line 14 from the detection voltage ΔVu of the AC voltage detectors 28u and 28u 'and the detection current Iu of the AC current detector 26u. The impedance detection circuit 30v is configured as impedance detection means for detecting the impedance of the AC transmission line 16 from the detection voltage ΔVv of the AC voltage detectors 28v and 28v 'and the detection current Iv of the AC current detector 26v. The impedance detection circuit 30w
Is the detection voltage ΔVw of the AC voltage detectors 28w and 28w '.
It is configured as impedance detecting means for detecting the impedance of the AC transmission line 18 from the detected current Iw of the AC current detector 26w. The detection values of the impedance detection circuits 30u to 30w are input to the impedance control circuits 34u to 34w, respectively, and the AC voltage detection values Vu, Vv, Vw and the AC current detection values Iu, Iw
v and Iw are input to the failure detection circuit 32, respectively. The failure detection circuit 32 detects the AC voltage detection values Vu, V
v, Vw and the AC current detection values Iu, Iv, Iw are configured as failure detection means for detecting that an accident such as ground fault or short circuit has occurred in the power system, and the detection output (detection signal) Fd is synchronized. Signal creation circuit 40, pulse phase shift circuit 42
Has been entered.

The impedance control circuits 34u, 34v,
34w calculates the firing phase angle (β) for each thyristor Thu to Thz according to the deviation between the impedance command value Zp and the detection value of each of the impedance detection circuits 30u, 30v, 30w, and follows the calculation result. It is configured as a command value generating means for generating command values (αu, αx, αv, αy, αw, αz) of the control angle. That is,
The impedance control circuits 34u, 34v, 34w are configured to perform a process for converting the firing phase angle β into a control angle (control delay angle) α. Specifically, 0 degree of the firing phase angle β is equivalent to 180 degrees of the control angle α. When actually firing each thyristor, the control angle α = 0 degrees is set as the synchronization reference point. Since it is necessary to set the firing timing, the firing phase angle β is converted to the control angle α. In this case, 1 is between the firing phase angle β and the control angle α.
Since there is a difference of 80 degrees, the control angle α is calculated by calculating the control angle α = π−β, and the calculated control angle α is output as a command value. The command values based on the outputs of the impedance control circuits 34u to 34w are input to the pulse phase shift circuit 42 via the switching circuit 36, respectively. The switching circuit 36 controls each of the impedance control circuits 34 u to 34 u according to the output pulse of the pulse phase shift circuit 42.
The command values output from w are sequentially switched and output to the pulse phase shift circuit 42. The pulse phase shift circuit 42 has a reference pulse signal S generated based on the synchronization pulse signal Sn detected by the synchronization signal detection circuit 38.
s has been entered.

The synchronizing signal detection circuit 38 detects an AC current detection value I detected by the AC current detectors 26u to 26w.
u, Iv, and Iw, and is configured as a synchronous pulse signal generating means for generating a synchronous pulse signal Sn by detecting a synchronous point (zero cross point) which is a zero point of each current. It is input to the creation circuit 40.

As shown in FIG. 3, the synchronizing signal generation circuit 40 includes a phase difference detection circuit 44, an operational amplification circuit 46, a bias power supply 48, an addition circuit 50, a switching circuit 52, a phase storage circuit 54, and a voltage control oscillation circuit 56. , A frequency dividing circuit (decoder) 58.

As shown in FIG. 4, the phase difference detection circuit 44 detects a phase difference Δθ between the synchronization pulse signal Sn output from the synchronization signal detection circuit 38 and the reference pulse signal Ss output from the frequency dividing circuit 58, The signal of the detected phase difference Δθ is output to the operational amplifier circuit 46. The operational amplifier circuit 46 controls and amplifies the phase difference Δθ to amplify it, and outputs a control voltage Ec corresponding to the phase difference Δθ. That is, the phase difference detection circuit 44 and the operational amplification circuit 46 are configured as control voltage generation means. Then, the control voltage Ec based on the output of the operational amplifier circuit 46 is added to the bias voltage from the bias power supply 48 in the adding circuit 50, and the added voltage is input to the switching circuit 52 and the phase storage circuit 54.

The switching circuit 52 includes the failure detection circuit 3
2 selects the control voltage Ec from the adder 50 before the failure detection signal Fd is input, and selects the control voltage Ec ′ stored in the phase storage circuit 54 when the failure detection signal Fd is input. The selected control voltage is output to the voltage control oscillation circuit 56 as a command value. The phase storage circuit 54 controls the control voltage Ec based on the output of the addition circuit 54.
Is stored as a voltage related to the phase difference Δθ for, for example, 10 ms, and this voltage is held as a control voltage Ec ′. Further, when the failure detection signal Fd is input, the value of the control voltage Ec ′ stored before the occurrence of the system failure is held until the failure detection signal Fd is released.

The control voltage oscillation circuit 56 changes the oscillation frequency in accordance with the control voltage selected by the switching circuit (control voltage selection means) 52, specifically, in proportion to the average value of the control voltage Ec or Ec '. The pulse signal is input to the frequency dividing circuit 58 as a voltage-controlled oscillating means for outputting a pulse signal corresponding to the oscillation frequency. The frequency dividing circuit 58 divides the output pulse signal of the voltage controlled oscillation circuit 56 into a pulse signal having a frequency six times the commercial frequency, and divides the frequency-divided pulse signal into a reference pulse signal Ss
As reference pulse signal generating means. That is, in order to generate reference pulse signals for the six thyristors Thu to Thz, the frequency oscillating at a high frequency is frequency-divided to six times the commercial frequency to generate the reference pulse signal Ss. .

The synchronizing signal generating circuit 40 is configured as a PLL (phase locked loop) circuit, and a deviation (phase difference) between the synchronizing pulse signal Sn and the reference pulse signal Ss.
When Δθ is subjected to first-order advance / delay control in the operational amplifier circuit 46, the operational amplifier circuit 46 outputs a control voltage Ec as shown in FIG.
A pulse signal having an oscillation frequency corresponding to the average voltage of the control voltage Ec is output, and this pulse signal is frequency-divided by the frequency dividing circuit 58 to a frequency six times the commercial frequency, whereby a reference pulse signal for each thyristor is obtained. Generated.

Here, the frequency of the system increases and the current Iu
Assuming that the zero point has advanced, the phase of the synchronization pulse signal Sn advances, so the phase difference Δθ due to the output of the phase difference detection circuit 44 increases, and the output Ec of the operational amplifier circuit 46 also increases. Therefore, the oscillation frequency of the voltage controlled oscillation circuit 56 increases, and the phase of the reference pulse signal Ss generated by the output of the frequency dividing circuit 58 also advances. In this way, control following the frequency of the system is performed.

On the other hand, when the frequency of the system falls,
Since the phase of the synchronization pulse signal Sn is delayed, the phase difference Δθ due to the output of the phase difference detection circuit 44 decreases, and the output Ec of the operational amplifier circuit 46 also decreases. For this reason, the oscillation frequency of the voltage controlled oscillation circuit 56 becomes low, and the phase of the reference pulse signal Ss due to the output of the frequency dividing circuit 58 is also delayed. In this way, control following the frequency of the system is performed.
That is, the synchronizing signal generation circuit 40 operates so that the reference pulse signal Ss output from the frequency dividing circuit 58 always follows the zero point of the system current and a certain phase difference.

The phase difference in the steady state is calculated by the operational amplifier circuit 4.
6 can be arbitrarily set by changing the bias voltage applied to the output Ec. That is, by arbitrarily adjusting the output voltage of the bias power supply 48, the oscillation frequency can be matched with the zero-degree point or the 180-degree point of the phase of the voltage across each of the series capacitors Cu to Cw.

On the other hand, the pulse phase shift circuit 42 shown in FIG.
The reference pulse signal Ss is shifted in accordance with the command value input from the switching circuit 36 to generate a firing pulse signal, and the phase shift means is configured to output the firing pulse signal to each of the thyristors Thu to Thz. .

Specifically, as shown in FIG. 5, the firing pulse signals of the thyristors Thu to Thz of each phase are U⇒Z⇒V
⇒X⇒W⇒Y, that is, thyristors Thu, T
π / 6 in the order of hz, Thv, Thx, Thw, Thy
It is late by each. For example, in the case of the U phase, the Ssu point is the generation timing of the reference pulse signal Ss generated by the synchronization signal generating circuit 40, that is, the phase of the voltage across the U-phase series capacitor Cu is 0 degree (command value α = 0 degree). And the command value generated by the impedance control circuit 34u is αu
, The command value αu in response to the reference pulse signal Ssu
The pulse Pu shifted by this amount is output from the pulse phase shift circuit 42 as a firing pulse signal for the thyristor Thu. When the firing pulse signal Pu is output, the output signal is switched by the switching circuit 36, and the command value αz is output from the impedance control circuit 34w. As a result, the pulse phase shift circuit 42 switches to the next reference pulse signal Ssz delayed by π / 6, and
Is output as a firing pulse signal Pz to the thyristor Thz. When the firing pulse Pz is output, the pulse phase shift circuit 42 outputs the next pulse from the reference pulse signal Ssz to π /
The pulse signal is switched to the reference pulse signal Ssv delayed by six, and a pulse signal obtained by shifting the reference pulse signal Ssv by the command value αv is output to the thyristor Thv as the firing pulse signal Pv. Hereinafter, similarly, the reference pulse signals Ssx, Ss
The firing pulse signals Px, Pw, Py obtained by shifting w, Ssy by the command values αx, αw, αy are sequentially output to the respective thyristors Thx, Thw, Thy at a timing delayed by π / 6.

When the ignition pulse signal is generated by the pulse phase shift circuit 42, when a system fault occurs, a reference pulse signal generated based on the control voltage Ec 'stored in the phase storage circuit 54 before the fault occurs. Therefore, since a firing pulse is generated, a firing pulse signal can be generated at the time of an accident in the same manner as before the accident, and each thyristor can be continuously operated.

In the above configuration, when compensating for the impedance of each of the transmission lines 14, 16, and 18 using the series compensator, the ignition phase angle for operating in the capacitive impedance region at the time of steady operation is determined. In the event of the accident described above, in order to suppress the overvoltage generated in the series capacitors Cu to Cw, a process is performed in which each thyristor is fully turned on to obtain a firing phase angle for operating in a capacitive impedance region. In this case, as shown in FIG. 6, the firing phase angle β is determined depending on whether the impedance command value Zp input to the control device 24 indicates the capacitive impedance Zc or the inductive impedance Zl.

FIG. 6 is a diagram in which the horizontal axis represents the impedance characteristic of each thyristor with respect to the firing phase angle, where the positive region indicates the capacitive impedance and the negative region indicates the inductive impedance. When the angle between 180 ° and 0 ° as the phase of the voltage across the series capacitor is represented by the firing phase angle β, when β = 0 °, the reactors Lu to L
Since no current flows through w, the impedance of the series compensator is the same as the impedance of the series capacitors Cu to Cw, Zc0 = 1 / ωC (ω = 2πf: commercial frequency).
It is. As the value of the firing phase angle β of the thyristor increases, the current flowing through the reactors Lu to Lw increases, and the capacitance and impedance increase up to the firing phase angle of βlim. βlim indicates a firing phase angle at which the series capacitor and the AC reactor resonate at a commercial frequency. At a firing phase angle exceeding this value, the current flowing through the reactors Lu to Lw becomes larger than the current flowing through the series capacitors Cu to Cw. , The impedance of the series compensator becomes an inductive impedance. Further, as the firing phase angle β increases, the inductive impedance decreases, and β =
At 90 degrees, each thyristor is fully conductive (full conduction). The impedance at this time is the parallel impedance of the AC reactor and the series capacitor, that is, the inductive impedance Z10. The impedance with respect to the firing phase angle β is described in the literature “Kato et al., 6,“ Study of Control Method of Thyristor Controlled Series Capacitor and Development of Reduced Model ””, IEEJ Transactions, Vol. 7
(July 1997) ", it can be obtained by the following equation from the ratio between the fundamental wave voltage and the fundamental wave current of the transmission line.

The impedance Xtcsc = πωL / (π
.omega.2LC-2.beta. + sin2.beta.) Thus, by adjusting the firing phase angle .beta., the impedance can be adjusted in a range from the capacitive region to the inductive region.

Here, as shown in FIG. 4, when the firing angle of each thyristor is controlled by the capacitive impedance, the voltage Vu across the series capacitor Cu is delayed by about 90 degrees from the detection current Iu.

If a three-phase ground fault occurs at the timing t = t0 shown in FIG. 4 while each thyristor is controlled in such a state, the fault detection circuit 32 detects an overcurrent, and the fault is detected in the system. Occurs, the timing t
At t1, control is performed to make each thyristor fully conductive, and each series capacitor is protected. At this time, the synchronization signal detection circuit 38 cannot detect the normal current zero point due to the fault current, and the operation of the phase difference detection circuit 44 also becomes abnormal. Therefore, a signal indicating a normal phase difference is not output from the phase difference detection circuit 44.

However, in the present embodiment, when a fault occurs in the system, the control voltage Ec ′ stored in the phase storage circuit 54 is selected by the switching circuit 52, so that the voltage control oscillation circuit 56 t
After = t1, a pulse having an oscillation frequency according to the control voltage Ec 'stored in the phase storage circuit 54 is output, and the oscillation frequency is maintained at the oscillation frequency before the accident. Therefore,
During the occurrence of the accident, the ignition pulse signal is generated in accordance with the reference pulse signal Ss as in the case before the accident, and each thyristor can be continuously operated.

Also, during the accident, each thyristor is controlled based on the reference pulse signal before the accident. The system remote from the accident point operates based on the movement of the generator regardless of the accident. Since the operation of the thyristor is also adjusted to the situation of the accident,
This is because the system can be quickly recovered from the accident by adjusting to the operation of the system or the generator before the accident.

As described above, according to the present embodiment, the thyristor can be operated stably both during and after an accident has been eliminated, thereby improving the system stability by speeding up the recovery of the system after the accident has been eliminated. Can be done.

The timing at which the switching circuit 52 switches from the selection of the control voltage Ec 'stored in the phase storage circuit 54 to the selection of the control voltage Ec by the output of the adding circuit 50, that is, the timing of resetting, is determined by the failure detection circuit 32. Or an accident elimination detection signal can be used. Further, in this case, a start timer means at the time of occurrence of an accident shown in FIG. 7A or a start timer means after the accident is eliminated shown in FIG. 7B can be used.

The timer means shown in FIG.
The output signal of the failure detection circuit 32 is input to the set terminal of the timer 60 and the flip-flop 62. The timer 60 responds to the failure detection signal Fd output from the failure detection circuit 32 and resets the flip-flop 62 when a set time has elapsed after the input of the failure detection signal Fd. The flip-flop 62 is set in response to the failure detection signal Fd of the failure detection circuit 32,
d is output. When reset by a signal from the timer 60, the switching circuit 52 is instructed to switch the selection of the control voltage. That is, when the failure detection signal Fd is no longer input from the flip-flop 62, the switching circuit 52 switches from the control voltage Ec ′ based on the output of the phase storage circuit 54 to the selection of the control voltage Ec based on the output of the adder circuit 50. . In addition, the set time of the timer 60, for example, the time from accident detection to accident removal,
Three cycles can be set.

FIG. 7 (b) takes into account the delay in returning to the normal state after the removal of the accident in the case of a major accident.
It is provided with an inverter 64, a timer 66, and a flip-flop 62. The inverter 64 inverts the level of the output signal of the failure detection circuit 32, and inputs the inverted signal to the timer 66. The timer 66 is started on the condition that the generation of the high-level failure detection signal Fd from the failure detection circuit 32 stops, that is, when the output level of the inverter 64 is inverted due to the elimination of the accident,
Then, when the set time has elapsed, the flip-flop 6
2 is reset. Thus, by using such timer means, it is possible to instruct the switching circuit 52 to switch after the accident is eliminated.

In the above embodiment, the case where the impedance of the transmission line is controlled has been described. However, the control may be performed using a current command value, a voltage command value, a power command value, or another command value instead of the impedance command value. The present invention can also be applied to a control system using other command values, with only the difference between the command value and the detection value serving as the feedback signal.

[0043]

As described above, according to the present invention,
In the event of a system failure, a reference pulse signal is generated based on the control voltage generated before the occurrence of the system failure, and the ignition pulse signal generated according to the reference pulse signal is supplied to the switching element. The operation of the switching element at the time of failure and at the time of failure elimination can be appropriately performed, and the recovery from a system failure can be accelerated.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a series compensation device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control device.

FIG. 3 is a block diagram of a synchronizing signal generation circuit.

FIG. 4 is a waveform chart for explaining the operation of the synchronization signal generation circuit.

FIG. 5 is a waveform chart for explaining the operation of the pulse phase shift circuit.

FIG. 6 is a characteristic diagram illustrating a relationship between a firing phase angle and impedance.

FIG. 7 is a diagram for explaining the configuration of a start timer unit when an accident occurs and a start timer unit after an accident is eliminated.

[Explanation of symbols]

Cu, Cv, Cw Series capacitors Lu, Lv, Lw AC reactor Thu, Thx, Thv, Thy, Thw, Thz thyristor 10, 12 AC system 14, 16, 18 AC transmission line 20u, 20v, 20w, 22u, 22v, 22w AC reactor 24 Control device 26u, 26v, 26w AC current detector 28u, 28v, 28w, 28u ', 28v', 28w '
AC voltage detector 30u, 30v, 30w Impedance detection circuit 32 Failure detection circuit 34u, 34v, 34w Impedance control circuit 36 Switching circuit 38 Synchronization signal detection circuit 40 Synchronization signal creation circuit 42 Pulse phase shift circuit 44 Phase difference detection circuit 46 Operational amplification Circuit 50 Addition circuit 52 Switching circuit 54 Phase storage circuit 56 Voltage controlled oscillation circuit 58 Frequency divider circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Isao Kota 20-1 Kita-Sekiyama, Odaka-cho, Midori-ku, Nagoya-shi, Aichi Prefecture Chubu Electric Power Co., Inc. (72) Inventor Yuji Yamazaki 20-1 Kitasekiyama, Midori-ku, Midori-ku, Nagoya City, Aichi Prefecture Chubu Electric Power Co., Inc. 5G066 DA04 FA01 FB08 FC01 FC11

Claims (8)

[Claims] 1. An AC reactor connected in series to an AC transmission line, an AC reactor connected in parallel to the series capacitor, and an AC reactor connected in series to the AC reactor, the AC reactor being responsive to a firing pulse signal. A switching element for controlling a phase of a flowing current, an electric signal detecting means for detecting an electric signal of the AC transmission line, and firing of the switching element according to a deviation between a command value and a detection value of the electric signal detecting means. Command value generating means for calculating a phase angle and generating a command value of a control angle according to the calculation result;
Failure detection means for detecting a failure in an AC system based on the electric signal of the AC transmission line, and synchronization pulse signal generation means for generating a synchronization pulse signal synchronized with the electric signal in response to the electric signal of the AC transmission line A control voltage generating means for generating a control voltage corresponding to a phase difference between the reference pulse signal and the synchronization pulse signal; and a fault in the AC system by the fault detecting means among the control voltages generated by the control voltage generating means. Control voltage storage means for storing a control voltage generated before detection, and selecting a control voltage stored in the control voltage storage means in response to a failure detection output of the failure detection means; Control voltage selection means for selecting a control voltage generated by the control voltage generation means; and a pulse signal having an oscillation frequency corresponding to the control voltage selected by the control voltage selection means. , A reference pulse signal generating means for generating a reference pulse signal according to an output pulse signal of the voltage control oscillating means, and a reference pulse signal generating means for generating a reference pulse signal according to a command value generated by the command value generating means. And a pulse phase shifter for generating a firing pulse signal by shifting the reference pulse signal according to (1) and outputting the firing pulse signal to the switching element. 2. A series capacitor inserted in series with an AC power transmission line, an AC reactor connected in parallel to the series capacitor, and an AC reactor connected in series with the AC reactor and connecting the AC reactor in response to a firing pulse signal. A switching element that controls a phase of a flowing current; a current detection unit that detects a current of the AC transmission line; a voltage detection unit that detects a voltage of the AC transmission line; a detection current of the current detection unit and the voltage detection Means for calculating the impedance of the AC transmission line from the detected voltage of the means, and calculating a firing phase angle for the switching element according to a deviation between an impedance command value and a value calculated by the impedance calculating means. Command value generating means for generating a command value of the control angle according to the result; Failure detection means for detecting a system failure, synchronization pulse signal generation means for generating a synchronization pulse signal synchronized with the electric signal in response to the electric signal of the AC transmission line, a reference pulse signal and the synchronization pulse signal, Control voltage generation means for generating a control voltage according to the phase difference of
A control voltage storage unit that stores a control voltage generated before the failure of the AC system is detected by the failure detection unit among the control voltages generated by the control voltage generation unit; and a failure detection output of the failure detection unit. Control voltage selection means for selecting the control voltage stored in the control voltage storage means in response, and otherwise selecting the control voltage generated by the control voltage generation means; and selecting the control voltage selected by the control voltage selection means. Voltage-controlled oscillating means for outputting a pulse signal having an oscillation frequency corresponding to a control voltage; reference pulse signal-generating means for dividing the output pulse signal of the voltage-controlled oscillating means to generate a reference pulse signal; The reference pulse signal generated by the reference pulse signal generating means is shifted according to the command value generated by the means to generate a firing pulse signal. Series compensator comprising a pulse phase shifting means for outputting a signal to the switching element. 3. An accident start timer means for responding to a failure detection output of the failure detection means and instructing the control voltage selection means to switch the selection of the control voltage when a set time has elapsed thereafter. The series compensator according to claim 1 or 2, wherein: 4. After removing an accident, the control voltage selection means is instructed to switch the selection of the control voltage when a set time elapses on condition that the generation of the failure detection output from the failure detection means is stopped. 3. The series compensator according to claim 1, further comprising a start timer. 5. An electric signal detecting means for detecting an electric signal of an AC power transmission line, and a deviation between a command value and a detection value of the ignition phase angle for a switching element inserted into the AC power transmission line. Command value generating means for calculating a control angle command value in accordance with the calculation result, a fault detecting means for detecting a fault in the AC system based on the electric signal of the AC transmission line, and A synchronizing pulse signal generating means for generating a synchronizing pulse signal synchronized with the electric signal in response to the electric signal of the electric wire, and a control voltage generating means for generating a control voltage corresponding to a phase difference between the reference pulse signal and the synchronizing pulse signal Means, control voltage storage means for storing a control voltage generated before a failure of the AC system is detected by the failure detection means among control voltages generated by the control voltage generation means, Control voltage selection means for selecting a control voltage stored in the control voltage storage means in response to a failure detection output of the detection means, and otherwise selecting a control voltage generated by the control voltage generation means; Voltage-controlled oscillating means for outputting a pulse signal having an oscillation frequency corresponding to the control voltage selected by the voltage selecting means, reference pulse-signal generating means for generating a reference pulse signal in accordance with an output pulse signal of the voltage-controlled oscillating means, Pulse phase shifting means for shifting the reference pulse signal generated by the reference pulse signal generating means in accordance with the command value generated by the command value generating means to generate a firing pulse signal and outputting the firing pulse signal to the switching element. A switching element control device provided. 6. A current detecting means for detecting a current of an AC power transmission line, a voltage detecting means for detecting a voltage of the AC power transmission line, and a voltage detected by the current detecting means and a voltage detected by the voltage detecting means. Impedance calculating means for calculating the impedance of the AC transmission line, and calculating a firing phase angle for a switching element inserted in the AC transmission line according to a deviation between an impedance command value and a calculated value of the impedance calculating means. Command value generation means for generating a control angle command value according to the result, failure detection means for detecting a failure of the AC system based on the electric signal of the AC transmission line, and responding to the electric signal of the AC transmission line. A synchronizing pulse signal generating means for generating a synchronizing pulse signal synchronized with the electric signal; and a control voltage corresponding to a phase difference between the reference pulse signal and the synchronizing pulse signal. Control voltage generating means for generating;
A control voltage storage unit that stores a control voltage generated before the failure of the AC system is detected by the failure detection unit among the control voltages generated by the control voltage generation unit; and a failure detection output of the failure detection unit. Control voltage selection means for selecting the control voltage stored in the control voltage storage means in response, and otherwise selecting the control voltage generated by the control voltage generation means; and selecting the control voltage selected by the control voltage selection means. Voltage-controlled oscillating means for outputting a pulse signal having an oscillation frequency corresponding to a control voltage; reference pulse signal-generating means for dividing the output pulse signal of the voltage-controlled oscillating means to generate a reference pulse signal; The reference pulse signal generated by the reference pulse signal generating means is shifted according to the command value generated by the means to generate a firing pulse signal. Switching element control device comprising a pulse phase shifting means for outputting a signal to the switching element. 7. An accident start timer means for responding to a failure detection output of the failure detection means and instructing the control voltage selection means to switch the selection of the control voltage when a set time has elapsed thereafter. The switching element control device according to claim 5 or 6, wherein 8. After the removal of an accident, the control voltage selection means is instructed to switch the selection of the control voltage when a set time has elapsed after the failure detection output from the failure detection means has stopped. 7. The switching element control device according to claim 5, further comprising a start timer unit.