JPS637140A - Reactive power compensator - Google Patents

Abstract

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

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a reactive power compensator.

(Prior Art) One of the functions of a reactive power compensator (hereinafter referred to as SVC) is to stabilize the system voltage of a power system.

FIG. 5 shows an example of an SVC installed in a power system. 1 indicates the power transmission end of the power system, 2 indicates the transmission N line, 3 indicates the power reception end, and 4 indicates the load. 5 is a reactor, 6 is a thyristor, and the reactor 5 and thyristor 6 are an example of a configuration of an SVC called a thyristor-controlled reactor. The part surrounded by broken mA is SvC. 7a is an auxiliary transformer (hereinafter referred to as PT)
8 is an SVC control circuit.

FIG. 6 is a block diagram showing the configuration of the control circuit 8 of FIG. 5, and its configuration and operation will be briefly explained.

9 is a voltage detection circuit, 10 is a setting device that indicates the reference voltage Vrer, and 11a is a pressure reducer. 12 is the system voltage V at the receiving end
A proportional-integral circuit or the like is normally used as a reactive power determining circuit that determines the reactive power Q to be generated by the SVC so that R is maintained at the reference voltage Vrer.

Reference numeral 13 denotes a firing angle determination circuit that determines the firing angle α of the thyristor 6 such that the SVC generates the reactive power Q. 14
is a gate pulse generation circuit (PG) that generates a gate pulse to the thyristor 6 whose firing angle is α.

Briefly explaining these functions, the system voltage VR at the receiving end is detected by the signal from the PT 7a and the voltage detection circuit 9, and the error voltage ΔVR, which is the difference from the reference voltage Vref indicated by the setting device 10, is detected by the subtracter. 11a.

Next, the reactive power determining circuit 12 outputs reactive power Q of the SVC such that the grid voltage VR is maintained at the reference voltage Vref.
is determined from the error voltage ΔVR.

Next, in the firing angle determination circuit 13, SvC is the reactive power Q
The firing angle α of the thyristor 6 for outputting is determined. Next, using the firing angle α which is the output of the firing angle determination circuit 13 in PGI 1, a gate pulse is formed taking into account the synchronization signal and the like.

The thyristor 6 is fired by this gate pulse, and Sv
C generates reactive power Q, and the receiving end system voltage VR is maintained at the reference voltage V ref. As explained above, this control loop can also be called an automatic voltage control circuit since it attempts to maintain the system voltage VR at the reference voltage Vref.

(Problems to be Solved by the Invention) However, maintaining the grid voltage VR at the reference voltage yrer is not necessarily the highest priority objective for SVC users. For example, the grid voltage VR is the reference voltage V
In some cases, priority is given to improving power transmission efficiency as long as it does not deviate too much from ref.

Moreover, from the viewpoint of response time, the control circuit that increases power transmission efficiency requires a much slower response than the automatic voltage control circuit, so it is possible to prevent the two from interfering with each other.

An object of the present invention is to provide an SVC that maintains the grid voltage at a voltage that does not deviate significantly from a reference voltage and improves power transmission efficiency.

[Configuration of the Invention (Means for Solving Problems)] In order to achieve the above object, the present invention provides a reactive power compensator that controls the system voltage to maintain it at a reference voltage. A power transmission efficiency improvement signal obtained from the difference voltage between the grid voltage at the installation point and the grid voltage at the other end via the transmission line is added to the reference voltage via a series circuit of a transfer function circuit and a limiter circuit. This is what I did.

(Function) As shown in FIG. 1, in the present invention, the power transmission efficiency improvement signal B is slowly transmitted to the limiter circuit by passing through the transfer function circuit C, and then the power transmission efficiency is improved by the limiter circuit. A certain limit value is imposed on the signal B, and then the reference voltage E
is added to form a new reference voltage. The automatic voltage control circuit G controls the SVC with this new reference voltage as a target.

(Embodiments of the Invention) Although the purpose is to improve power transmission efficiency, the meaning of power transmission efficiency differs depending on the user of SvC. For example, if there is a transmission end and a power receiving end via a power transmission line as shown in Figure 5, when the grid voltage at the sending end and the grid voltage at the receiving end are equal, the loss in the transmission line is close to the minimum. Become. Therefore, when using the difference voltage obtained by subtracting the system voltage at the SVC installation point (for example, the receiving end) from the system voltage at the other end (for example, the sending end) via the transmission line from the point of view of the SVC installation point as a power transmission efficiency improvement signal, An example will be explained using FIG. 2.

Components having the same symbols as those used in the description of the conventional example have the same functions. 11b is a subtracter, 15 is a transfer function circuit such as a first-order delay circuit, 16 is a limiter circuit, and 17 is an adder. The portion surrounded by the broken line H corresponds to the present invention.

In FIG. 2, Vs indicates the system voltage at the power transmission end, and although it may be a voltage value of each similarity law, a representative value such as an average value is preferable. First, the subtracter 11b detects the difference voltage Δv5 between the power transmission end voltage VS and the reference voltage V ref. Basically, this Δ■5 is added to the reference voltage yrer to form a new reference voltage ■8. Since the new reference voltage vN is equal to the sending end voltage 5, the receiving 'l@II' voltage VR tends to become equal to the sending N end voltage Vs. However, it is undesirable for the power transmission efficiency improvement control loop to interfere with the automatic voltage control loop, and since the power transmission efficiency improvement may work very slowly compared to the automatic voltage control circuit, the differential voltage ΔVs is directly connected to the reference voltage Vrer. The signal is not added to the signal, but is transmitted slowly through the first-order delay circuit 15. Furthermore, if the sending end voltage v5 deviates greatly from the reference voltage vrer, that is, if ΔVs becomes very large, the SVC tries to maintain the receiving end voltage VR at a voltage that deviates greatly from the reference voltage y rer, which is not desirable, so the limiter A limit is imposed on the value of ΔVs that is added to the reference voltage vref by the circuit 16.

As explained above, the sending end voltage ■5 and the reference voltage ■ref
If the differential voltage ΔVs is within the limit of the limiter circuit 16, the new reference voltage v2 becomes equal to the power transmission mN pressure Vs after a time based on the time constant of the first-order lag circuit 15. Further, if the differential voltage ΔVs is greater than or equal to the limit value of the limiter circuit 16, the new M quasi-voltage vN tends to approach the power transmission end voltage Vs within the range allowed by the limit value. and a new reference voltage vN
After the voltage is determined, the sending end voltage VR is maintained at the new reference voltage V by the same effect as explained in the conventional example.

As described above, the system voltage at the SVC installation point (power receiving end) is maintained at a voltage equal to or close to that at the power transmitting end within a range that does not deviate significantly from the reference voltage ref, and power transmission efficiency can be improved. In particular, if the automatic voltage control circuit is controlled according to the law of similarity, and Vs in Fig. 2 is a representative value such as an average value, even if the power transmission efficiency improvement control circuit of the present invention is added, there will be no difference in the voltage of each phase. It has little negative effect on the operation of the automatic voltage control loop which improves the balance.

The above explained the case where the meaning of improving power transmission efficiency is interpreted as reducing power transmission loss, but when using SvC,
When it is desired to maintain the power factor at the VC installation point to the reference power factor, for example power factor = 1, or when it is desired to maintain the reactive power flowing out to the transmission line at the SVC installation point to the reference reactive power There is also.

FIG. 3 shows an example of a configuration to satisfy the former requirement.

In the figure, 18 is a power factor detection circuit, 1 is a reference power factor pF
This is a setting device that indicates rer. The part surrounded by broken line 1 corresponds to the main part of the present invention.

In Figure 3, from the signals of PT7a and CT7b, SvC
The power factor PF at the installation point is detected by the power factor detection circuit for one day, and the difference power factor ΔPF between the reference power factor PF ref indicated by the setting device 19 and the power factor PF is detected by the subtractor 11b. By passing this ΔPF through the first-order delay circuit 15, the change in ΔPF is transmitted slowly, and ΔPF is added to the reference voltage V ref within the limit allowed by the limiter circuit 16, forming a new reference voltage ■N. . The operation of the automatic voltage control circuit is the same as that described in the conventional example, and the voltage at the SVC installation point is maintained at the new reference voltage (8).

As explained above, the system M voltage at the SvC installation point is maintained without greatly deviating from the reference voltage, and the power factor is also improved.

FIG. 4 shows an example of a configuration for satisfying the latter requirement mentioned above. In the figure, 2o is a reactive power detection circuit, and 2) is a setting device that indicates the reference reactive power V A Rref. Broken line J
The portion surrounded by corresponds to Modification 2 of the present invention.

In Fig. 4, from the signals of PT7a and CT7b, the SVC
The reactive power VAR to the transmission line at the installation point is detected by the reactive power detection circuit 20, and the reference reactive power M A indicated by the setting device 2) is detected.
The difference △VAR between Rver and reactive power VAR is the subtracter 1
1b. By passing this ΔVAR through the first-order delay circuit 15, the change in ΔVAR is transmitted slowly, and within the range allowed by the limits of the limiter circuit 16, ΔVAR is changed based on the value of ΔVAR! #Lightning voltage A New reference voltage V added to Rrer
N is formed. The operation of the automatic voltage control circuit is the same as that explained in the conventional example, and the voltage at the SVC installation point is the new reference voltage V.
maintained at N.

As explained above, the system voltage at the SvC installation point is maintained at a voltage that does not deviate significantly from the reference voltage, and reactive power to the power transmission line can also be controlled.

[Effects of the Invention] As explained above, according to the present invention, it is possible to maintain the grid voltage without significantly deviating from the reference voltage, and to improve transmission loss, power factor, or control reactive power flowing into the transmission line. can.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the main parts showing one embodiment of the present invention,
2 to 4 are block diagrams showing different embodiments of the present invention, FIG. 5 is a single line diagram of a reactive power compensator, and FIG. 6 is a circuit for controlling a conventional reactive power compensator. FIG. 1...Power transmission end, 2...Power transmission line, 3...Power receiving end, 4
Load, 5 Reactor, 6 Thyristor, 7a Auxiliary transformer, 7b Auxiliary current transformer, 8
... Control circuit, 9... Voltage detection circuit, 10... Setting device, 11a... Subtractor, 12... Reactive power determining circuit, 13... Firing angle determining circuit, 14... Gate pulse generation circuit, 15... Transfer function circuit, 16... Limiter circuit, 17... Adder, 18... Power factor detection circuit,
19... Setting device, 2o... Reactive power detection circuit, 2)
...Setting device. Applicant's representative Patent attorney Takehiko Suzue Figure 1 8' Figure 5 1゜Figure 6

Claims (4)

[Claims] (1) In a reactive power compensator that controls the grid voltage to maintain it at a reference voltage, power is transmitted obtained from the difference voltage between the grid voltage at the installation point of the reactive power compensator and the grid voltage at the other end via the transmission line. A reactive power compensator characterized in that an efficiency improvement signal is added to the reference voltage via a series circuit including a transfer function circuit and a limiter circuit. (2) The reactive power compensator according to claim 1, wherein the transfer function circuit comprises a combination of a lead circuit and a delay circuit. (3) The reactive power compensator according to claim 1, wherein the power transmission efficiency improvement signal is a signal obtained by taking the difference between the power factor at the installation point of the reactive power compensator and a reference power factor. . (4) The reactive power compensator according to claim 1, wherein the power transmission efficiency improvement signal is a signal obtained by taking the difference between the reactive power at the installation point of the reactive power compensator and the reference reactive power. .