Reactive power compensation PLC control system-PLC, reactive power compensation, the control system

Published: 15th March 2011
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Abstract: The importance of reactive power compensation and parallel Capacitor The principle of the reactive compensation analysis of common compensation and control system problems, actual project introduced PLC Reactive power compensation control system hardware and software design.

Key words: reactive power compensation; PLC; power factor; capacitor

1 Introduction Recent years, the rate of increase in China's power installed capacity, greatly easing the power shortage situation. With the power supply increases, the system line losses will increase. According to statistics, the power system reactive power loss of the total generation capacity of up to 20% to 30%, that is about 1 / 4 of the power generation capacity will be used to offset the process of power transmission and distribution losses. Therefore, the lower the power factor, the more negative on the power system operation, mainly the following two aspects:

1) Generator Transformer rated apparent power SN = UNIN, it represents the rated capacity of equipment, is numerically equal to allow the issuance of the maximum power. Because the generator rated active power is given under

P = UIcos When the load power factor cos = 1 , PN = SN, its capacity was fully utilized. When the load power factor cos <1, the generator's voltage and current rating not allow more than, obviously, when the active power generator can send smaller, no reactive power is greater. The greater the reactive power, circuit and Power supply Energy exchange between the size of the larger generators to generate energy are not fully utilized. Meanwhile, generators and transformers prime mover supporting equipment can not be fully utilized.

2) in the case of certain voltage, active power of load when transporting certain, the lower the power factor, the greater the current transmission lines. Not only increased the line pressure drop, but also increased the lines of power loss.

Thus, to improve power factor or reactive power compensation, the development of the national economy has a very important significance.

2 parallel capacitor reactive power compensation
1) compensation principle The majority of practical engineering inductive load, the power factor are relatively low, inductive load shunt capacitors to improve power factor of the main methods.

Inductive load currents ahead of the power supply voltage, the capacitive load the current lags the supply voltage, so ahead of the current with the hysteresis currents can complement each other prior to the point from the power supply capacitors in parallel (or grid) to reduce the reactive power absorbed , and the load is capacitive reactive power compensation of the inductive reactive power load. When the network capacity is fixed, the reactive power reduction, which can greatly improve the power factor.

2) Compensation and Control Commonly used method of compensation: one is to focus on compensation (compensation capacitors installed in the substation or distribution focus room, facilitating the centralized management); one is the combination of centralized and decentralized compensation (as part of compensation capacitors installed at substations the other part of the installation of the larger departments in the inductive load or workshop. This approach flexible, easy to adjust, and can reduce the enterprise supply and distribution line losses.

Compensation control method used: Electrical equipment under load conditions, estimates the compensation capacitance, choose the appropriate reactive Compensator And use the grading contactor manually switch capacitors. This control method obviously does not meet the requirements of industrial control automation.

Discrete components assembled by the automatic control equipment, components of this product range, heavy equipment, large, complex lines, unreliable and difficult to repair failure.

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