JP3319206B2 - Control method of self-excited var compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system of a self-excited reactive power compensator of an inverter specification used for suppressing voltage fluctuations and measures against flicker in a three-phase power system.

[0002]

2. Description of the Related Art A control method of a self-excited reactive power compensator of an inverter specification installed in a three-phase power system is based on adjusting a system voltage phase of a power system, directly detecting reactive power, and obtaining a compensation current command value. And a B method for obtaining a compensation current command value by subtracting the active power component included in the load current of the power system from the load current.

In the case of the former A system, a relatively simple and low-cost control circuit can be used, but a delay in the compensation current command value occurs due to a delay in the response of the low-pass filter for compensating the unbalance of the reactive power. As a result, there is a problem that a compensation error occurs. This inconvenience is reduced in the case of the B method. That is, in the B method, a reactive current and a three-phase unbalanced active power component are obtained by performing a matrix operation, a three-phase / two-phase conversion, or the like on the load current and the system voltage of the three-phase power system, and obtain the reactive power and the three-phase unbalanced active power component. There is known a method of obtaining a three-phase compensation current command value by performing a matrix operation, two-phase / three-phase conversion, or the like on a balanced active power component.

[0004]

However, the B method has a problem in that the number of circuits for matrix operation increases, the whole reactive power compensator becomes complicated, and the cost as hardware increases. In the conventional control method of the self-excited var compensator of the inverter specification, if there is an active power flow between the var compensator and the power system, the DC voltage of the inverter fluctuates in the active power flow and However, there is a possibility that the system will stop due to a failure, and a reliability problem remains.

It is an object of the present invention to provide a control system which can realize a highly reliable self-excited reactive power compensator having an inverter specification with a simple control circuit configuration and low cost.

[0006]

SUMMARY OF THE INVENTION The present invention provides a compensation current command in a self-excited reactive power compensator of an inverter type which obtains a compensation current command value of reactive power by subtracting an active power component from a load current of a three-phase power system. In the value detection method, the active power obtained from the system phase voltage and load current of each of the three phases of the power system is averaged to obtain a DC signal equivalent to the three-phase equilibrium component of the active power, and the three-phase A balanced balanced sine wave signal is obtained from the system phase voltage, and the balanced effective current component created by amplitude-modulating the balanced sine wave signal with a gain obtained from the DC signal is subtracted from the load current to compensate for each of the three phases. The above object is achieved by obtaining the current command value.

[0007]

[Working] The active power obtained from the system voltage and the load current is averaged by a low-pass filter or the like to obtain a DC component, and the fundamental component balanced active current component obtained from the DC component and the system phase voltage synchronized sine wave signal is loaded. When subtracted from the current, a compensation current command value capable of compensating for reactive power including unbalanced active power is obtained. Inverter-specific self-excited var compensators with such a control method can be configured with simple circuits such as a low-pass filter and a phase-locked loop, and with a small number of circuits. It becomes possible.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The algorithm of the control method of the present invention will be described with reference to the main circuit of FIG. 1 and the compensation current command value detection circuit of FIG.

As shown in the main circuit of FIG. 1, a load 3 is connected to a three-phase three-wire system bus 2 having a three-phase AC system power supply 1, and the load 3 is connected to the system bus 2 between the load 3 and the system power supply 1. A self-excited var compensator 4 using an inverter 5 is provided.

The outline of the control system of the present invention by the reactive power compensator 4 is as follows. Active power is obtained from the system voltage V of each of the three phases and the load current i, and a balanced active current component in the load current i is detected from the active power. And this balanced effective current component is
Is to compensate for the reactive power including the imbalance compensation of the active power by compensating the current component subtracted from the power component. Such reactive power compensation is performed based on the three-phase compensation current command values i _RC , i _SC , and i _TC output from the detection circuit of FIG.

First, the system phase voltages V _R , V _S , V _T of each phase of the three-phase three-wire system bus 2 and the load currents i _R , i _S , i _T
Are multiplied by the multiplier 7 of each phase and added by the adder 8 to obtain the three-phase active power P from the following equation.

[0012] _{P = V R · i R +} V S · i S + V T · i T

Next, the DC component P 'of the DC component is removed from the active power P by removing the AC component, for example, by a low-pass filter (LP).
F) Determined through 9. This DC signal P ′ corresponds to a fundamental-wave balanced active power that is a three-phase balanced component of the active power P.

On the other hand, the three-phase system phase voltage V_R , V_S , V_T 
From the balanced sine wave signal S of unit amplitude synchronized with this.
_R , S_S , S_T Ask for. For example, a phase locked loop (PL
L) The system phase voltage V of each phase at 10_R , V_S , V_T Zerok
Take out the clock signal synchronized with the loss
The sine wave signal obtained from the sine wave generation circuit 11 according to the signal
Amplitude is modulated by unit amplitude to correct the balance of the system phase voltage synchronized sine wave.
Sine wave signal S_R , S_S , S _T Get.

Thus, the balanced sine wave signal S _{R of} each of the three phases,
S _S and S _T are multiplied by a gain K obtained from a DC signal P ′ corresponding to the fundamental wave balanced active power by a multiplier 12 for each phase, and balanced active current components i _RP and i _SP in which three phases are synchronized. , I _TP
Ask for. The three-phase gain K in this case is K = (2/3
V _P ) P ′. Incidentally, V _P is the grid voltage amplitude.

Therefore, the three-phase balanced effective current components i _RP , i
_In the self-excited var compensator 4 for compensation other than _SP and i _TP , the balanced active current components i _RP , i _SP and i _TP are respectively determined from the load currents i _R , i _S and i _T of the three phases. The value subtracted by the phase-by-phase subtractor 13 is the compensation current command value _iRC , _iSC , _iTC.
Is detected as

As described above, the compensation current command values i _RC , i _SC ,
By _calculating i _TC , the reactive power compensator 4 compensates for reactive power including unbalance compensation in active power on the load side of the system bus 2. In addition, the reactive power compensator 4 can perform harmonic compensation together with unbalanced active power. However, when harmonic compensation is unnecessary, it can be dealt with using a harmonic elimination filter.

[0018]

According to the present invention, the active power is obtained from the system voltage and the load current of the power system, and the fundamental wave balanced active current component is obtained from the DC component and the system phase voltage synchronous sine wave signal to obtain the active power from the load current. When subtracted, a compensation current command value that can compensate for reactive power including unbalanced active power is obtained, so inverter configuration that can be configured with simple circuits such as a low-pass filter and a phase locked loop circuit and that can easily reduce equipment costs Can be provided. Also, even if there is an active power flow between the reactive power compensator and the grid, the effect on the reactive power compensation of the grid is reduced and
High-speed compensation and improvement in compensation accuracy of the reactive power compensator can be achieved.

[Brief description of the drawings]

FIG. 1 is a main circuit diagram of a power system for explaining a control method according to the present invention.

FIG. 2 is a control circuit diagram showing a control algorithm for detecting a compensation current command value in the self-excited var compensator of FIG. 1;

[Explanation of symbols]

1 three-phase system power supply 2 Three-phase system bus 3 Load 4 self-excited reactive power compensator 5 inverter V system voltage i load current P active power P 'DC signal V _R, V _S, the system phase voltage V _T three-phase i _R , I _S , i _T Three-phase load current S _R , S _S , S _T balanced sine wave signal i _RP , i _SP , i _TP balanced active current component i _RC , i _SC , i _TC compensation current command value

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05F 1/70 H02J 3/18

Claims (1)

(57) [Claims] 1. A control method of a self-excited reactive power compensator of an inverter specification for obtaining a reactive current command value of reactive power by subtracting an active power component from a load current of a three-phase power system. The active power obtained from the system phase voltage and load current of each phase is averaged to obtain a DC signal equivalent to the three-phase equilibrium component of the active power, and a synchronized sine wave signal synchronized from the system phase voltages of the three phases is obtained. The balanced effective current component created by amplitude-modulating the balanced sine wave signal with the gain obtained from the DC signal is subtracted from the load current to obtain compensation current command values for each of the three phases. A control method for a self-excited var compensator, wherein a reactive power is compensated including a real power.