JPH096446A - Control method for self-exiting reactive power compensation device - Google Patents

Abstract

PURPOSE: To provide a reactive power compensation effect even when a system linkage three-phase transformer employs different connection system for the primary and secondary windings in the self-exciting reactive power compensation device (SVC). CONSTITUTION: A load current IL of a three-phase three-wire system bus 2 is detected and a compensation object current ICREF of a reactive power component of the current is obtained by a compensation current arithmetic block, and the compensation object current ICREF is given to a phase conversion block, in which matrix arithmetic operation processing is conducted based on a connection system of a primary winding 6a and a secondary winding 6d of a transformer 6 and the ratio N of the number of turns to obtain an inverter output current command value IIREF. The inverter output current command value IIREF is used to control an inverter 5 to supply an inverter output current II to the secondary winding of the transformer 6, then a primary compensation current IC satisfies a relation of IC=-(compensation object component in load current IL) to compensate the reactive power of the system bus 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for a self-excited var compensator of an inverter type, which generates a compensating current for canceling a reactive current generated by load fluctuation in a three-phase three-wire system busbar of an electric power system.

[0002]

2. Description of the Related Art A self-excited reactive power compensator installed in a system power source such as a substation and a three-phase three-wire type power system having a fluctuating load such as an arc furnace or an electric railway load, a three-phase inverter and a three-phase transformer Some are equipped with vessels. An example of the main circuit is shown in FIG. 5 and explained. A load 3 and a self-excited reactive power compensator (hereinafter, referred to as self-excited SVC) 4 are installed on a three-phase three-wire system bus bar 2 having a three-phase AC system power supply 1. To be done. Self-excited S
The VC 4 is composed of a three-phase inverter 5 and an interconnection three-phase transformer 6'installed on the output side thereof. The primary side of the transformer 6 ′ is connected to the three-phase three-wire system bus bar 2, and the secondary side is connected to the inverter 5.

The transformer 6 of the self-excited SVC 4 is a three-phase transformer of the same connection system, in which the primary connection 6'a and the secondary connection 6'b are triangular connection (delta connection) or star connection, and in FIG. Triangular / triangular connection method is shown, but star-shaped / star connection method is also used. The self-excited SVC 4 suppresses the voltage fluctuation of the system bus 2 by generating compensation power that cancels the reactive power of each of the three phases generated in the system bus 2 due to the load fluctuation.

That is, a control block of the self-excited SVC 4 is shown.
6 and the conventional control method of this is demonstrated. Load fluctuation
Load current I of the system bus 2 at_L Detect that
The reactive power component therein is calculated by the compensation current calculation block 7.
Control signal obtained by the compensation current calculation block 7 (compensation target
Current) is the inverter output current command value I_I ^REFAs INVA
The output current I of the inverter_I Get.
Inverter output current I _I Can flow to the secondary side of the transformer 6
Compensation current I on the primary side of the transformer 6_C Of the transformer 6
Primary and secondary have the same triangle / triangle connection or star / star connection
Inverter output current I because it is a single connection system_I And phase,
Have the same amplitude (when the winding ratio is 1), I_I = I_C But
To establish. As a result, I_C =-(Load current I_L The compensation target component in the
The force is compensated.

[0005]

The reactive power compensation effect of the self-excited SVC 4 on the system bus 2 is that the primary connection 6'a and the secondary connection 6'b of the three-phase transformer 6 for interconnection are star-shaped. It is of the same connection type, such as a star connection or a triangle / triangle connection, and can be obtained by establishing I _I = I _C. In other words, if the primary connection 6'a and the secondary connection 6'b of the transformer 6 are of different connection systems such as star / triangle connection or triangle / star connection, the inverter output current I _I Thus, the amplitude and phase of the compensation current I _C differ, and I _I = I _C no longer holds, so that the reactive power compensation effect cannot be obtained.

Therefore, in the conventional self-excited SVC,
The three-phase transformer for interconnection uses a model in which the primary and secondary connections are the same. However, such limitations and restrictions on the model of the transformer may have a disadvantage for the user of the self-excited SVC. In addition, due to the circumstances of other devices, there may occur a situation in which a transformer having a different primary and secondary connection method must be used in the self-excited SVC, and such a situation may occur. Although it is possible to deal with it on the main circuit side, there was a problem in terms of capital investment.

The object of the present invention is not to deal with the main circuit side of the power system even if the three-phase transformer for interconnection in the self-excited SVC has different primary and secondary winding systems. It is an object of the present invention to provide a control method of a self-excited SVC capable of obtaining a reactive power compensation effect.

[0008]

According to the present invention, an inverter output current corresponding to a current to be compensated for reactive power in a load current of each of the three phases flowing in a system bus of a three-phase three-wire power system is transformed into a three-phase transformer. A method of controlling a self-excited reactive power compensator for compensating reactive power generated by load fluctuation of a system bus with a compensation current of the primary side of the same transformer obtained by flowing to the secondary side of the transformer,
In order to achieve the above object, the phase-amplitude conversion is performed on the current to be compensated in the load current of each of the three-phase by matrix calculation processing based on the connection method of the primary connection and secondary connection of the three-phase transformer and the winding ratio. The inverter output current command value is obtained, and the inverter output current based on this inverter output current command value is made to flow to the secondary side of the transformer.

[0009]

[Function] The current to be compensated in the load current of each of the three phases is detected, and the current to be compensated is phased by matrix calculation processing based on the connection method of the primary connection and secondary connection of the three-phase transformer and the winding ratio. When the inverter output current command value obtained by amplitude conversion is used to drive and control the inverter, and the inverter output current is passed to the secondary side of the transformer, the primary side current of the transformer becomes the primary side and the secondary side of the transformer. When the wiring method is the same or different, the compensation current of the phase and amplitude cancels the current to be compensated in the load current, and the range of usable models of the three-phase transformer is expanded.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below with reference to FIGS.

FIG. 1 shows an example of a main circuit of a power system in which a self-excited SVC 4 is installed. The self-excited SVC 4 is composed of a three-phase inverter 5 and an interconnection three-phase transformer 6 installed on the output side thereof. To be done. The transformer 6 includes a primary connection 6a and a secondary connection 6b.
Are different connection methods, for example, the primary connection 6a is a triangular connection and the secondary connection 6b is a star connection. When an inverter output current I _I similar to that shown in FIG. 5 is supplied to the secondary side of such a transformer 6, the compensating current I _C on the primary side becomes I _I ≠ I _C due to the difference between the primary and secondary connection methods, As a result, I _C ≠-(compensation target component in the load current I _L ), and reactive power compensation for each of the three phases of the system bus 2 due to load fluctuation cannot be performed.

Therefore, in the present invention, the control block shown in FIG.
The self-excited SVC 4 is controlled as shown in the lock. Ma
Instead, the load voltage of the system bus 2 is changed when the load changes as before.
Flow I_LIs detected and the power to be compensated for the reactive power component in it is detected.
Flow I_C ^REFIs calculated by the compensation current calculation block 7. Next,
Compensation target current I obtained in compensation current calculation block 7_C ^REFTo
The phase conversion block 8 connects the primary connection 6a of the transformer 6 to the secondary connection.
Performs matrix calculation processing based on the wiring method of the wire 6b and the winding ratio.
Inverter output current command value I_I ^REFAsk for. Soshi
This inverter output current command value I_I ^REFWith inverter
5 to control the inverter output current I_I Secondary of transformer 6
If it is made to flow to the side, the compensation current I on the primary side _C Is I_C =-(Load current I_L Compensation target component in), and reactive power compensation of the system bus 2 is possible.
It works.

The matrix calculation processing of the above-described method of the present invention will be described from the current relationship between the primary side and the secondary side of the transformer 6 in FIG. U-phase current I _CU , V-phase current I _CV , W-phase current I _CW , and UV-phase current I in each phase of the three-phase primary connection 6a of the triangular connection
_The following three equations are established between the _UV , VW interphase current I _VW and the WU interphase current I _WU .

I _UV = I _WU + I _CU I _VW = I _UV + I _CV I _WU = I _VW + I _CW

Further, each of the three phases of the secondary connection 6b of the star connection
Phase current I at_IU, V-phase current I _IV, W-phase current I_IWWhen
UV interphase current I of primary connection 6a_UV, VW Interphase current I_VW,
WU interphase current I_WUThe following three expressions are established between the two. However,
N is the transformer turns ratio between the primary connection 6a and the secondary connection 6b.
It is.

I _UV = -N x I _IU I _VW = -N x I _IV I _WU = -N x I _IW

Here, the three-phase system voltage V _U of the system power supply 1,
Three-phase load currents I _LU , I _LV , and I for V _V and V _W
As shown in the vector of FIG. 4, when _LW is a current with a delay of 90 ° (reactor load) and the current components I _UV , I _VW , and I _WU are removed from the above equation 6, the inverter output current is calculated from the following determinant. The relationship between I _I and compensation current I _C can be obtained.

[0018]

[Equation 1]

Therefore, the compensation current calculation block 7 in FIG. 2 finds the compensation target current I _C ^{R EF} in the load current I _L , and applies this to the above determinant to set the inverter output current command value I _I.
^Ask for ^REF . That is,

[0020]

[Equation 2]

Compensation target current I _C ^REF for each of the three phases by the determinant of
When the inverter output current command value I _I ^REF for each of the three phases is obtained from the above, and the inverter 5 is drive-controlled based on this inverter output current command value I _I ^REF , the primary side compensation current I _C of the transformer 6 becomes Phase conversion and amplitude conversion are performed in accordance with the different connection methods of the primary side and the secondary side of No. 6, and I _C = − (compensation target component in the load current I _L ) and reactive power compensation becomes possible.

In the above embodiment, the primary connection 6a of the transformer 6 is used.
Is a triangle connection and the secondary connection 6b is a star connection,
The present invention can be applied in the above manner even if the transformer is a star-shaped primary connection and a triangular connection secondary connection. Further, in the case of a transformer in which the primary connection and the secondary connection are the same connection type, it is not necessary to perform the above matrix calculation processing, but the present invention can be applied, and a provision for changing the model of the transformer can be provided. .

[0023]

According to the present invention, the current to be compensated for in the load current of each of the three phases is subjected to matrix calculation processing based on the primary and secondary connection methods of the three-phase transformer and the transformer turns ratio. Since the inverter drive current was controlled by the inverter output current command value obtained by converting the phase and amplitude, the primary side current of the transformer due to the inverter output current is the same or different between the primary side and secondary side of the transformer. In any case, it becomes the compensation current of the phase and amplitude that cancels the compensation target current in the load current,
Reactive power compensation becomes possible. As a result, a three-phase transformer of a model having a different connection method on the primary side and the secondary side can be used for the self-excited var compensator, and the selection range of the model of the transformer is expanded. In addition, when a model with different primary and secondary wiring is used for the three-phase transformer, the main circuit side of the power system is driven by the inverter without any special measures for reactive power compensation. Only by taking countermeasures for arithmetic processing of the control system, therefore, reactive power compensation countermeasures can be advantageously performed in terms of capital investment.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of a main circuit of a three-phase power system for explaining the method of the present invention.

FIG. 2 is a control block diagram of the main circuit of FIG. 1 according to the method of the present invention.

FIG. 3 is an equivalent circuit diagram showing an example of a three-phase transformer and current relationship in the self-excited reactive power compensator for the main circuit of FIG.

FIG. 4 is a vector diagram of voltage and current of each of the three phases in the main circuit of FIG.

[Fig. 5] Equivalent circuit diagram of main circuit of three-phase power system according to conventional specifications

FIG. 6 is a control block diagram of the main circuit of FIG. 5 according to a conventional control method.

[Explanation of symbols]

2 System bus 3 Load 4 Self-excited reactive power compensator 5 Inverter 6 Transformer 6a Primary connection 6b Secondary connection I _L Load current I _C compensation current I _C ^REF Compensation target current I _I Inverter output current I _I ^REF Inverter output current command value

Claims (1)

[Claims] 1. An inverter output current corresponding to a reactive power compensation current in a load current of each of the three phases flowing through a system bus of a three-phase three-wire power system is supplied to a secondary side of the three-phase transformer. This is a control method for a self-excited reactive power compensator that compensates the reactive power generated by the load fluctuation of the system bus with the obtained compensation current on the primary side of the same transformer. Of the three-phase transformer primary connection and secondary connection method and the phase-amplitude conversion by matrix calculation processing based on the winding ratio to obtain the inverter output current command value, and the inverter output based on this inverter output current command value A method of controlling a self-excited var compensator, characterized in that a current is caused to flow to the secondary side of a transformer.