JPS5926177B2 - Reactive power control method for AC systems including DC parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reactive power control system for an AC system including a DC portion.

Generally, DC power transmission systems are equipped with phase adjustment equipment to adjust reactive power, and this equipment (power capacitors, shunt reactors) is automatically operated to maintain reactive power within an appropriate range. .

This is because the reactive power generated by the converter is absorbed by the phase adjusting device to reduce power loss due to the power transmission load.
In a DC power transmission system, in order for a forward converter to operate normally, current must flow with a lag behind voltage on the AC side, and this is a type of load that takes a delayed reactive component.
The more AC power is converted into DC power, the more a delay reactive component is required, and if this is not compensated for, the AC voltage will drop to 0, making it impossible to send the required active power to the inverter. Further, in order to operate the inverter normally, it is necessary to advance the current with respect to the negative alternating current voltage on the output side.

For a positive alternating current voltage, the delay current is 5. Therefore, the inverter is a device that requires a delayed current, and unless this is compensated for, the AC voltage will drop and the desired power cannot be sent out. Since both forward and inverse converters require lagging reactive power, a reactive power control device is installed to compensate by supplying phase-advanced reactive power in order to prevent a voltage drop in the AC system.

FIG. 1 shows a frequency conversion station system as an example of a power transmission system including a DC portion.

In this system), the 50H2 bus bar and the 60H2 bus bar are connected by a frequency conversion system that uses two sets each of a breaker 1, a variable voltage transformer 2, and a converter 3. The area between the three is the DC part. and,
The thyristor converter 3 is configured with a three-phase bridge connection.
The control of the converter is phase control that controls the phase of the gate signal applied to the valve. The basic control method is constant power control or constant current control on the forward converter (rectifier) side, and constant margin angle control on the inverse converter (inverter) side. FIG. 2 shows a control circuit block diagram. The reactive power consumption of the converter is calculated using the following formula.

Q-Pdtanθ (MVar)...
(1) Q: Reactive power consumption Pd: Converted power α: Control angle u: Weight angle P: Number of rectification phases Id: DC current X: Commutation reactance EdO: Direct/inverse conversion of DC voltage when not controlled The required reactive power for the delay of the device is proportional to the control angle of the valve, and the required ratio of reactive power to DC power is 30-50% for a forward converter and 40-60% for an inverse converter.

Normally, the DC system is connected to a large-capacity AC system, so there is no need for a phase-advanced reactive power supply device to compensate for all 60 (F6) of the maximum required reactive power.

Generally, 30% is supplied from the AC system, and the remaining 30% (L
is supplied from a reactive power supply device. Jubei's reactive power control device is a control method that detects the amount of reactive power consumed by the converter, compares it with a reference value, and issues operating commands to the phase adjustment equipment.

FIG. 3 is a reactive power control block diagram, in which the reactive power detection circuit converts the amount of reactive power into a DC voltage. The reactive power level detection circuit compares the reactive power of the actual system with various set levels of reactive power to determine which level it is at. The operation command discrimination circuit receives a level signal detected by the reactive power level detection circuit, and outputs an operation signal to the phase adjusting device in accordance with the signal. The equal frequency leg circuit is a circuit that determines and sends out operating commands for the power capacitor Sc and shunt reactor ShR to which equipment, and is designed to provide equal frequency control. However, controlling the phase adjustment equipment based on the detected value of reactive power in this way has drawbacks such as the need for a circuit configuration for detection and a delay in operational response.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a reactive power control method that controls phase adjustment equipment without detecting reactive power in an actual system.

To achieve this objective, the present invention provides a reactive power control method that controls phase adjustment equipment according to the power setting value of the AC/DC converter.

An embodiment of the present invention will be described below with reference to FIG. FIG. 4 is a block diagram showing the control circuit of the present invention.

That is, the power setting value signal Pdp given to the thyristor converter control circuit is taken out and given to the reactive power control device.
This reactive power control device consists of a required reactive power detection circuit, an operation command discrimination circuit, a power capacitor Sc, a shunt reactor ShR, etc. frequency control circuit, and a power capacitor Sc.
and gives ON/OFF commands to shunt reactor ShR. Here, the reactive power consumption of the thyristor converter is determined by the above equation 1, and since α and u are approximately constant during normal operation, it can be determined by the following equation.

That is, Q-K1・Pd・・・・・・・・・(2)(
K1=Tanθ).

The converted power Pd is approximately equal to the power setting value Pdp.
Also, since it is Pd-Ed-1d, it can be expressed as the following equation. QkiK1・Pdp=K1・Id−Ed +K1・Idp−Ed=K2・Idp・・・・・・・・・
・(3)(K2-K1・Ed).

Therefore, Q is determined by Pdp or Idp,
Reactive power control can be performed using the power set value Pdp or current set value Idp of the conversion device without detecting actual reactive power. As described above, in the present invention, the phase adjustment device is controlled by the power setting value of the thyristor conversion device, so that a reactive power detection device and related circuits are not required, and the device configuration is simple. .

Furthermore, since there is no response delay associated with detection, controllability is improved.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the system configuration of a frequency converter station, Figure 2 is a block diagram showing the control circuit of a thyristor converter used in a power transmission system including a DC section, and Figure 3 is the configuration of a conventional reactive power control device. FIG. 4 is a block diagram of the reactive power control device according to the present invention. 1... Switching or disconnection, 2... Transformer, 3...
...Thyristor converter.

Claims (1)

[Claims] 1. In a method of controlling reactive power supplied from a phase modifier to a system that converts power obtained from an AC system into DC and then converts it into AC and transmits the power, a method that controls reactive power supplied from a phase adjustment equipment The required reactive power detection circuit detects the reactive power corresponding to the input power set value or current set value, and receives the output signal of this required reactive power detection circuit. Reactive power in an AC system including a DC part, characterized in that a reactive power control device is configured from an operation command discrimination circuit that outputs an operation signal that outputs an operation signal to a phase modifier according to the magnitude of an output signal. control method.