JP2867171B2 - Power control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a power control device that controls a power flow between interconnected systems or between a power supply and a system.

(Prior Art) It is an important subject to transmit a power flow through a more economical and stable route, and various methods have been already proposed. For example, in the United States, power flow control is performed using a phase shift transformer. In this case, however, control of the amount of power flow is performed by switching taps of the transformer.

Furthermore, by performing the AC → DC → AC conversion using the converter, any power flow (active power) can be controlled. In this case, however, inverter equipment having the same capacity as the active power to be passed is required.

(Problems to be Solved by the Invention) As is clear from the above description, an apparatus using a phase shift transformer can apply an arbitrary voltage.
Not only is the tap switching operation complicated, but the increase in active power is gradual and time-consuming. In the AC → DC → AC conversion, the installed capacity of the inverter becomes large.

The present invention has been made in order to solve the above-mentioned drawbacks, and an object of the present invention is to provide a power control device which is a simple facility and capable of controlling the power flow while maintaining the stability of the system.

[Structure of the Invention] (Means and Actions for Solving the Problems) In order to achieve the above object, the present invention relates to a power system control device that performs power flow control between systems interconnected via a transformer. A semiconductor converter that takes in the input voltage of
Means for introducing a voltage value and a phase angle controlled by the semiconductor converter to a secondary side of a transformer interconnecting between systems through a phase shift transformer.

Therefore, by arbitrarily changing the output voltage value of the semiconductor converter and the phase with respect to the system voltage, the power flows of the active power and the reactive power of the system can be arbitrarily controlled.

(Example) Hereinafter, an example is described with reference to drawings.

FIG. 1 is a configuration diagram of an embodiment of a power control device according to the present invention.

In FIG. 1, reference numeral 1 denotes a power system control device,
The three are connected via transformers 11-1 and 11-2. 12 is a semiconductor converter (inverter device), is connected to the grid 2 via a transformer 4, the voltage V _c of different phase voltages and 90 degree phase by the phase shift of the voltage of the semiconductor converter 12 and a transformer 13 It occurs, which via a transformer adds to system voltage V _2.
13-1 and 13-2 are transformers for phase shift voltage injection,
It is connected to the neutral point of each phase winding of the transformer 11-2. 5
Is a PT, and 6 is a CT, which is input to the control unit 7.

 Next, the operation will be described.

In the power system, the movement of power is represented by the following equation (1).

P = V _r · V _s sin θ / X (1) where V _r , V _s … Voltage at both ends of the line θ …… Phase difference X …… Reactance of the line In this case, voltages V having 90 ° phase difference added to the input voltage V ₂ and _c is (FIG. 2 (a)). The amount of phase shift is controlled at high speed by the output voltage of the semiconductor converter.

FIG. 2 (b) is a vector diagram showing active / reactive power after control.

Now, assuming that the maximum value of the output voltage of the converter is V _cm , the phase shift range is ± sin ^-1 (V _cm / V ₁ ), and the maximum controllable power is given by the following equation (2).

P _m = V ₁ · V _cm / X (2) The ratio α between P _m and the converter installed capacity P _cm is given by the following equation (3).

However, X _pu ... Reactance expressed by the unit method From equation (3), it is understood that when X _pu is small, a large power can be controlled by an extremely small capacity converter.

If the inverter output voltage value and its phase angle are arbitrarily controlled, not only the active power but also the reactive power can be simultaneously controlled at a high speed.

[Effects of the Invention] As described above, according to the present invention, a phase difference between interconnected systems is controlled at high speed by using a semiconductor converter, and power flow control corresponding to the phase difference is performed. The following effects are obtained.

 Active power can be controlled very quickly.

Since the inverter only needs to generate the voltage of the phase shift difference, the installed capacity of the inverter is smaller than the electric power to be passed.

Arbitrary active power and reactive power can be controlled by arbitrarily changing the phase with respect to the inverter output voltage value and the system voltage.

The insulation strength can be reduced by connecting the inverter side circuit to the neutral point side of the star connection transformer.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a power control device according to the present invention, and FIG. 2 is a vector diagram of input / output voltages after control. DESCRIPTION OF SYMBOLS 1 ... Power control device, 2,3 ... Power system 4 ... Transformer, 5 ... PT 6 ... CT, 7 ... Control part 11 ... Transformer, 12 ... Semiconductor converter 13 ... Transfer Transformer for phase voltage injection 14 ... System impedance

Claims (2)

(57) [Claims] 1. A power system control device for controlling a power flow between systems interconnected via a transformer, comprising: a semiconductor converter for receiving one input voltage of the system; and a voltage value controlled by the semiconductor converter. And a means for introducing a phase angle to a secondary side of a transformer interconnecting between systems through a phase shift transformer. 2. The power control device according to claim 1, wherein the voltage value and the phase angle controlled by the semiconductor converter are input near a neutral point of the star-connected transformer.