JPH09233702A - Power system stabilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the power system and improve reliability by controlling the ignition of a pair of thyristors, based on the power deviation from the reference power to the transmission power of a linked line, or the current deviation from the reference current to the transmission current of the linked line. SOLUTION: Transmission power is obtained with a power detection means 6 by line currents and system voltage, and the reference voltage generated by a reference power setting means 10 is subtracted from these to draw out a power deviation, and reverse voltage is generated by a power control means 9. An ignition control means 5 generates the ignition pulses of thyristors 4a and 4b, using the plurality of a line current, the capacity voltage, and reverse voltage. As a result, the system can be stabilized by suppressing the trembling of the power system even at accident of the system. What is more, the power detection means 6 can be omitted by constituting it such that it draws out the current deviation by subtracting the reference current from the line current, using a reference current setting means, in place of the reference power setting means 10, in case that the phase difference between the systems is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a series capacitor compensation system which inserts a series capacitor into an AC power system to compensate for line reactance of a transmission line, and suppresses transient phenomena in the power system and fluctuations in power flow. The present invention relates to a device for enhancing the stabilization effect of a power system.

[0002]

2. Description of the Related Art In a power system, the line reactance increases as the power transmission distance increases. Due to this line reactance, there are problems that reactive power consumption of the transmission line increases, transmission loss increases, or transmission power is limited. Conventionally, a method of inserting a series capacitor into a transmission line has been adopted to compensate for line reactance, but when a system failure occurs, an overvoltage occurs in the series capacitor and power fluctuation cannot be suppressed. As a countermeasure against this, a pair of thyristors connected in antiparallel with the reactance are connected in series, and reactive power adjusting means in parallel with the capacitor is connected in series with the transmission line, and the firing phase of the thyristor is changed to change the line reactance. A power system stabilizing device for compensating for the above has been proposed.

FIG. 6 is a block diagram showing a conventional power system stabilizing device disclosed in, for example, Japanese Patent Laid-Open No. 57-20128. 1 _a, 1 _b is a power system, 2 _a, 2 _b are tie-line,
Reference numeral 3 is a transformer, 4 is reactive power adjusting means, 5 is ignition control means, 6 is power detecting means, and CT ₁ is line current detecting means. The primary winding of the transformer 3 is connected in series with the interconnection lines 2 _a and 2 _b, and the reactive power adjusting means 4 is a pair of thyristors connected to the secondary winding of the transformer 3 and connected in antiparallel. _4a ,
4 and _b and a reactor 4 made of _c series connection constitutes in this series connection with a capacitor 4 _d connected in parallel.

Next, the operation will be described. The reactive power adjusting means 4 changes the equivalent impedance by changing the control angle α of the thyristors 4 _a and 4 _b , and the reactor 4 _c.
Capacitor 4 for forward bias current and reactor current I _l
It is a means for adjusting the current I _c of _d , and thereby adjusts the amount of reactive power consumption (supply). Now both power grids 1
_a, 1 phase difference between _b is [delta], a current of interconnection lines are to the transmission from the power system 1 _a to 1 _b in I _s, consider the case where the reactive power adjusting means 4 is operating in the capacitive. Thyristor 4 _a,
When the control angle α of 4 _b is reduced, both the current I _l of the reactor 4 _c and the current I _c flowing through the capacitor 4 _d increase, and the terminal voltage of the reactive power adjusting means 4 increases. Since the reactive power adjusting means 4 is connected in series to the power system via the transformer 3, it can not only cancel the line reactance like a series capacitor, but also adjust it in a stepless manner.
FIG. 7 is a vector diagram showing this state, where V _a and V _b are the back voltages of the power systems 1 and 2, V _h is the system voltage at the connection point between the transformer 3 and the interconnection line, and X ₁ and X ₂ are the connection voltages. Line reactances of the system lines 2 _a and 2 _b and X _c are equivalent reactances of the reactive power adjusting means 4. The voltage V _s applied to the transformer 3 has a reverse polarity to the reactance voltage drop I _s X ₁ or I _s X _{2 of the line,} and the current I _s can be increased by that amount, and the transmission power P increases.

The transmitted power P is represented by P = V _a · V _b · sin δ / (X ₁ + X ₂ + X _c ), and the equivalent reactance X _c of the reactive power adjusting means 4
The transmission power P can be continuously controlled by adjusting the value of (4) within an appropriate range of positive and negative. Normally, in order to increase the transmitted power P, X _c has a negative value, that is, in the range in which the reactive power adjusting means 4 operates capacitively.
Adjust the control angle α for _a and _b . Interconnection line power detection means 6
The electric power fluctuation is detected by the thyristor, the control angle α of the thyristor is obtained based on the electric power fluctuation, and the thyristor 4 _a , 4
_{If the b} switching signal is generated and the ignition timing is appropriately controlled, the power system can be operated stably. When the phase difference δ between the grids is small, the transmitted power P is almost proportional to the current I _s, so the current detection means can be used instead of the power detection means 6.

[0006]

Since the conventional power system stabilizing device is configured as described above, it is possible to suppress the power fluctuation of the power system and reduce the voltage fluctuation of the power system. However, there are problems that the method for controlling the firing of the thyristor is difficult and that the thyristor may malfunction depending on the conditions of the power system. In order to make the equivalent impedance of the series capacitor device variable, a method of sequentially bypassing multiple capacitors connected in series with a thyristor has also been proposed, but overvoltage may occur in the capacitor and the device becomes large. There is a problem such as becoming. In addition, there is a problem that a specific control method for stabilizing the power system and further improving reliability is not clear.

The present invention has been made in order to solve the above-mentioned problems, and further improves the stability and reliability of the power system, and further downsizes the device to stabilize the power system, which is easy to manufacture. The purpose is to obtain a chemical conversion device.

[0008]

A power system stabilizing device according to the present invention comprises a series connection body composed of a pair of thyristors and a reactor connected in reverse parallel to each other, and a capacitor connected in parallel with the series connection body. In the power system stabilizing device for connecting reactive power adjusting means to be connected in series to the interconnection line connecting the electric power systems, and adjusting the transmission time of the interconnection line by adjusting the ignition timing of the thyristor. The ignition control is performed on the pair of thyristors based on the power deviation from the preset reference power for the transmission power of the above or the current deviation from the preset reference current for the transmission current on the interconnection line.

Further, an inversion voltage proportional to the power deviation or the current deviation is generated, and at the time when the current polarity of the interconnection line is positive and the absolute value of the voltage between the terminals of the capacitor becomes smaller than the inversion voltage, one of the pair of thyristors is formed. To the other of the pair of thyristors when the current polarity is negative and the voltage between the terminals of the capacitor becomes smaller than the inversion voltage. Furthermore, the expansion rate of the voltage between the terminals of the capacitor by the firing control of the thyristor is the target compensation coefficient, the ratio of the reactance of the capacitor to the line reactance is the target line compensation degree, and the target is calculated from the transmission current of the interconnection line and the voltage between the terminals of the capacitor. The inversion voltage is corrected by obtaining a correction amount for maintaining the compensation coefficient and the target line compensation degree.

Further, based on the result of adding the integrated value from the time when the voltage between the terminals of the capacitor has a negative peak to the time when the voltage has a positive peak to the inversion voltage, an ignition pulse for one of the pair of thyristors is generated. A firing pulse for the other of the pair of thyristors is generated based on the result of subtracting the integrated value from the time when the voltage between the terminals of the positive peak reaches the time of the negative peak to the negative peak. is there.

Further, the ignition pulse is generated after passing through the voltage limiter means for limiting the inversion voltage or the corrected inversion voltage to a desired magnitude. Further, the ignition phase limiter means for limiting the generation time point of the ignition pulse is provided in the desired phase range of the voltage between the terminals of the capacitor.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of embodiments of a power system stabilizing device according to the present invention will be described below with reference to the drawings. The reference numerals used in each figure are the same as or similar to those of the conventional power system stabilizing device shown in FIG. 6, and the description of the overlapping functions and actions is omitted.

Embodiment 1 Hereinafter, a first embodiment of a power system stabilizing device according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a power system stabilizing device according to the present invention. Figure, T represents the voltage detecting means for detecting the system voltage V _h of the reactive power adjusting means 4 and the tie line 1 _a connection point, 5 in the ignition control means, comparing means 5 _a, the line current polarity discrimination means 5 _b , firing pulse generating means 5 _c . 6 is power detection means, 7 is capacitor voltage detection means, 9 is power control means, and 10 is reference power setting means.

Next, the operation will be described. The point that the equivalent impedance is changed and the amount of reactive power consumption (supply) is adjusted by adjusting the control angle α of the thyristors 4 _a and 4 _b is the same as in the conventional power system stabilizing device.
That is, by changing the current I _c of the capacitor 4 _d in the bias component proceeds reactor current I _l of the reactor 4 _c to adjust the equivalent impedance. The terminal voltage V _c of the capacitor 4 _d has a polarity opposite to that of the line reactance voltage drop I _s X ₁ or I _s X _2, and accordingly the line current I _c.
It becomes possible to increase _s , and the transmission power P increases. The equivalent impedance _Xc of the reactive power adjusting means 4 is adjusted to a desired range to control the transmitted power P. FIG. 2 is an operation waveform diagram showing an operation state of each unit.

Next, a method of adjusting the equivalent impedance X _c will be described. The peak value of the capacitor voltage when the thyristors 4 _a and 4 _b are not ignited is V _cp , the peak value of the line current is I _sp , the equivalent impedance is X _c , and the firing angle of the thyristors 4 _a and 4 _b is θ. Then, the following relationship holds. (Θ = π−α) X _c = (1-sin θ) / ωC + V _ref / √2I _srm Here, V _ref = (I _sp / ωC) · (ω / (ω ₀ ² −ω
² )) · (ω ₀ cos θ · tan (ω ₀ θ / ω) −ωsi
nθ). However, ω _t1 = −θ, ω _t2 = θ, ω ₀ = 1
/ √ (LC). In the above equation, V _ref is called an inversion voltage, and the equivalent impedance X _c can be adjusted by changing this inversion voltage V _ref . The inversion voltage V _ref is generated from the deviation between the transmitted power and the reference power.

From the line current I _s and the system voltage V _h , the electric power detection means 6 obtains the transmitted electric power P, and the reference electric power generated by the reference electric power setting means 10 is subtracted from this to derive the electric power deviation and the electric power control means. The inversion voltage V _ref is generated by 9. The ignition control means 5 uses the polarity of the line current I _s , the capacitor voltage V _c and the inversion voltage V _ref to generate the ignition pulse for the thyristors 4 _a and 4 _b . Generation logic of the thyristor 4 _a and 4 _b of the ignition pulses is as follows. (1) the polarity of the line current I _s is positive, the capacitor voltage V
_When the absolute value of _c becomes smaller than the inversion voltage V _{ref, the} ignition pulse of the thyristor 4 _a is generated. (2) the polarity of the line current I _s is negative, the capacitor voltage V
_{When c} becomes smaller than the inversion voltage V _ref , the thyristor 4
Generate the firing pulse for _b . By performing firing control of the thyristor 4 _a and 4 _b as described above, to suppress the sway of the electric power system even when a system fault can be stabilized operation of the power system. If the phase difference δ between grids is small, the power and current are almost proportional,
If the reference current setting means is used instead of the reference power setting means 10 and the reference current is subtracted from the line current I _s to derive the current deviation, the power detection means 6 can be omitted.

In the above description, the inversion voltage V _ref is generated on the basis of the power deviation, but the ratio of the reactance of the capacitor to the preset line reactance (hereinafter referred to as line compensation degree) and the capacitance of the capacitor. Configured to automatically adjust the compensation amount according to the ratio of the equivalent reactance of the reactive power adjusting means to the reactance (hereinafter referred to as the compensation coefficient, which can also be regarded as the expansion rate of the capacitor voltage due to thyristor firing control) By doing so, it is possible to adjust the capacitor voltage within an appropriate range, suppress fluctuation of the power system even in the event of a system failure, and stabilize the power system. FIG. 3 is a block diagram showing a power system stabilizing device having such a configuration. In the figure, 11 is a target compensation degree control means, 12 is a compensation coefficient setting means, and 13 is a line compensation degree setting means. The line reactance is X _l (where X _l = X ₁ + X ₂ ),
The reactance of capacitor X _cl, the equivalent reactance of the reactive power adjusting means X _c Distant, line compensation of h _l, respectively the compensation coefficient _{h k h l = X cl /} X l h k = X c / X cl definition To do.

Let I _{srm be} the effective value of the line current, V _{cp be} the peak value of the capacitor voltage when the thyristor is not _ignited, and V _{cph be} the peak value of the capacitor voltage when the thyristor is ignition controlled. It can be expressed as X _cl = h _l · X _l V _cp = √2 · I _srm · X _cl h _k = V _cph / V _cp . If the correction value of the inversion voltage V _ref for setting the capacitor voltage and the line compensation degree h _l to the target values is V _refh , then V _refh = (h _k -1) V _cp = (1-1 / h _k ) V It can be _obtained as _cph . In the target compensation degree control unit 11 obtains the correction value V _REFH adding the inversion voltage V _ref, it may be generated firing pulses of thyristors 4 _a and 4 _b on the basis of the inversion voltage V ■ _ref corrected.

Further, the fluctuation of the power system due to the low frequency resonance caused by the disturbance of the power system or the system accident is suppressed, and the capacitor voltage V _c is prevented from being asymmetrical between positive and negative and overvoltage, thereby stabilizing the power system. Therefore, the inversion voltage V _ref can be configured to be corrected based on the capacitor voltage V _c . FIG. 4 is a block diagram showing a power system stabilizing device configured to correct the inversion voltage _Vref based on the capacitor voltage Vc. The voltage control means 8, the result of integrating up time consisting of the time when the capacitor voltage V _c becomes the negative peak and positive peak and a positive correction amount [Delta] V _{ref +,} The capacitor voltage V _c is a positive peak The result of integration from the time point to the time point at which the negative peak is reached is the negative correction amount ΔV _ref- , and the inversion voltage V
inversion voltage after the correction plus the correction amount [Delta] V _{ref +} in _ref V _{ref +}
The ignition pulse of each of the thyristors 4 _b may be generated based on the corrected inversion voltage V _ref- of the thyristor 4 a _obtained by subtracting the correction amount ΔV _ref- from the inversion voltage V _ref of the thyristor 4 _a .

Further, the configuration for automatically adjusting the compensation amount according to the preset line compensation degree and the compensation coefficient and the configuration for correcting the inversion voltage V _ref based on the capacitor voltage V _c have been described. It is also possible to realize a power system stabilizing device that integrates both functions. In this case, the inversion voltage V _ref is corrected in accordance with the line compensation degree and the compensation coefficient as in the case shown in FIG. 3, and then the correction amount Δ based on the capacitor voltage V _c is further obtained as in the case shown in FIG.
_Corrected by V _{ref +} and ΔV _ref- , thyristor 4 _a
And 4 _b firing pulses may be generated. With this configuration, the power system stabilizing device described with reference to FIGS. 3 and 4 is also provided, and the fluctuation of the power system is suppressed even when the power system has a low cycle resonance or a system accident due to disturbance, The power system can be stabilized.

Furthermore, in the event of a system failure or when the capacitor is turned on again, power fluctuations and capacitor voltage fluctuations may suddenly increase. In such a case, in the above configuration, the firing angle θ of the thyristors 4 _a and 4 _b becomes large and the current and voltage of the capacitor may become excessive. In order to prevent such a situation from occurring, a limiter for limiting the absolute value of the inversion voltage V _ref to a desired range may be provided inside the ignition control means 5. Of course, regarding the power system stabilizing device shown in FIGS. 1, 3 and 4,
It goes without saying that the same effect can be obtained by providing the same limiter.

Furthermore, depending on the conditions of the power system,
If the capacitor voltage is distorted, the thyristor ignition may malfunction. In such a case, a malfunction can be prevented by providing a limiter for the firing phase of the thyristor together with a limiter that limits the absolute value of the inversion voltage. A thyristor firing prohibited section is set on the basis of the zero point of the capacitor voltage V _c detected by the ignition pulse generating means 5 _c , and even if there is a firing signal in this prohibited section, it is prevented from firing. A firing phase limiter may be provided so as to fire when the phase is reached. If this condition is specifically shown, it is as shown in FIG. The thyristor conduction period T _c, the capacitance of the capacitor C, the inductance of the reactor as L, if _{T 2 = 2 · T c =} 2π√ (LC), usually _{(T / 2-T 2/} 4) <T since set to _c <T / 2, when the capacitor voltage V _c and the inverted voltage V _ref is equal from the zero point of the capacitor voltage V _c (T / 2-
If there between T _2/4) (at time point _{T / 2-T 2/4} ), when the inverted voltage and the capacitor voltage V _c becomes equal, when in the shaded part of the figure at the time You can fire each.

Although all the power system stabilizing devices according to the present invention have been described as having the reactive power adjusting means inserted in series in the power transmission line, regarding the line reactance compensation,
It goes without saying that this is not essentially different from the one inserted in series in the transmission line through the transformer as shown in FIG.

[0024]

According to the first aspect of the present invention, the reactive power adjusting means is composed of a series connection body composed of a pair of thyristors and a reactor connected in antiparallel with each other, and a capacitor connected in parallel with the series connection body. Is connected in series to the interconnection line that connects the electric power systems, and the thyristor firing timing is adjusted to adjust the transmission power of the interconnection line. Since a pair of thyristors are controlled to fire based on the power deviation from the specified reference power or the current deviation from the preset reference current with respect to the transmission current of the interconnection line, the power system can be swayed even in the event of a system failure. It can suppress and stabilize the operation of the power system.

According to the invention of claim 2, in addition to the invention of claim 1, an inversion voltage proportional to the power deviation or the current deviation is generated, and the current polarity of the interconnection line is positive and the voltage across the terminals of the capacitor is An ignition pulse for one of the pair of thyristors when the absolute value becomes smaller than the inversion voltage, and an ignition pulse for the other of the pair of thyristors when the current polarity is negative and the voltage between the terminals of the capacitor becomes smaller than the inversion voltage. Since it is generated, it is possible to suppress the fluctuation of the power system due to the low-frequency resonance due to the disturbance of the power system or the system accident, and to prevent the capacitor voltage from becoming positive-negative asymmetric and causing an overvoltage.

According to the invention of claim 3, in addition to the invention of claim 2, the expansion ratio of the voltage between the terminals of the capacitor by the ignition control of the thyristor is the target compensation coefficient, and the ratio of the reactance of the capacitor to the line reactance is the target line. As the compensation level, the correction amount for maintaining the target compensation coefficient and the target line compensation level is calculated from the transmission current of the interconnection line and the voltage between the terminals of the capacitor to correct the inversion voltage. It is possible to adjust and stabilize the power system by suppressing the fluctuation of the power system even in the event of a system failure.

According to the invention of claim 4, in addition to the invention of claim 2 or claim 3, the integrated value from the time when the voltage between the terminals of the capacitor has a negative peak to the time when it has a positive peak is an inverted voltage. Based on the result of adding the ignition pulse to one of the pair of thyristors based on the result of addition to the inversion voltage, the integrated value from the time when the voltage between the terminals of the capacitor reaches the positive peak to the time when the voltage reaches the negative peak is subtracted from the inversion voltage. Since the ignition pulse for the other of the pair of thyristors is generated respectively, it is possible to prevent the capacitor voltage Vc from becoming positive-negative asymmetry and generating an overvoltage.

According to a fifth aspect of the present invention, in addition to the second to fourth aspects of the present invention, the ignition pulse is further applied through a voltage limiter means for limiting the inversion voltage or the corrected inversion voltage to a desired magnitude. Since it was generated
It is possible to prevent the occurrence of a situation in which the current and voltage of the capacitor become excessive due to the expansion of the firing angle of the thyristor at the time of a system fault or when the capacitor is turned on again.

According to a sixth aspect of the present invention, in addition to the second to fifth aspects, firing phase limiter means is provided for limiting the generation time point of the firing pulse within the desired phase range of the voltage between the terminals of the capacitor. Therefore, it is possible to prevent the malfunction of the thyristor ignition due to the distortion of the capacitor voltage or the like which occurs depending on the condition of the power system.

[Brief description of drawings]

FIG. 1 is a block diagram showing a power system stabilizing device according to the present invention.

FIG. 2 is an operation waveform diagram showing an operation state of each unit in FIG.

FIG. 3 is a block configuration diagram showing a modified example of the power system stabilizing device according to the present invention.

FIG. 4 is a block diagram showing another modification of the power system stabilizing device according to the present invention.

FIG. 5 is an operation explanatory view for explaining a modified example of the power system stabilizing device according to the present invention.

FIG. 6 is a block diagram showing a conventional power system stabilizing device.

FIG. 7 is a vector diagram during operation of a conventional power system stabilizing device.

[Explanation of symbols]

1 _a , 1 _b Power system 2 _a , 2 _b Interconnection line 4 Reactive power adjusting means 5 Firing control means 5 _a Comparing means 5 _b Polarity determining means 5 _c Firing pulse generating means 6 Power detecting means 8 Voltage control means 9 Power control means 10 Reference power setting means 11 Target compensation degree control means 12 Compensation coefficient setting means 13 Line compensation degree setting means

Claims (6)

[Claims] 1. A interconnection system for connecting between power systems, a reactive power adjusting means comprising a series connection body composed of a pair of thyristors and a reactor connected in antiparallel to each other and a capacitor connected in parallel with the series connection body. In a power system stabilizing device that is connected in series to a line and adjusts the ignition timing of the thyristor to adjust the transmission power of the interconnection line, the power from a preset reference power for the transmission power of the interconnection line. An electric power system stabilizing device, wherein ignition control is performed on the pair of thyristors based on a deviation or a current deviation from a preset reference current with respect to a transmission current of the interconnection line. 2. The inversion voltage proportional to the power deviation or the current deviation is generated, and the current polarity of the interconnection line is positive, and the absolute value of the inter-terminal voltage of the capacitor becomes smaller than the inversion voltage. An ignition pulse is generated for one of the pair of thyristors, and the ignition pulse is generated for the other of the pair of thyristors when the current polarity is negative and the voltage between the terminals of the capacitor becomes smaller than the inversion voltage. The power system stabilizing device according to claim 1. 3. The transmission rate of the interconnection line and the transmission current of the interconnection line are defined as a target compensation coefficient, and a ratio of a reactance of the capacitor to a line reactance is an expansion rate of a voltage between the terminals of the capacitor by ignition control of the thyristor. The power system stabilizing device according to claim 2, wherein a correction amount for maintaining the target compensation coefficient and the target line compensation degree is obtained from the voltage between the terminals of the capacitor to correct the inversion voltage. 4. A firing pulse for one of the pair of thyristors based on a result of adding an integrated value from a time point when a voltage between terminals of the capacitor has a negative peak to a time point when the voltage has a positive peak to the inversion voltage. The ignition pulse for the other of the pair of thyristors is generated based on the result of subtracting the integrated value from the time when the voltage between the terminals of the capacitor has a positive peak to the time when the voltage has a negative peak, from the inversion voltage. The power system stabilizing device according to claim 2 or 3, wherein 5. The firing pulse is generated afterwards via a voltage limiter means for limiting the inversion voltage or the corrected inversion voltage to a desired magnitude. The power system stabilizing device according to claim 1. 6. The ignition phase limiter means for limiting the generation time point of the ignition pulse in a desired phase range of the voltage between the terminals of the capacitor, according to claim 2 or claim 5. The described power system stabilizing device.