Research On Voltage And Reactive Power Control System In Substations Based On The PLC

The requirement to the electric power supplying quality is increasing with the development of industry and the improvement of people's standard of living. Voltage is a primary technological fingerpost of electric power quality and closely related with reactive power. The importance of the integrated control for voltage and reactive power is clarified in this paper. The achievement, problems and trend of development in this field are summarized. be aimed at the problems of the integrated control for shunt capacitors and Tap Change Under Load (TCUL) transformers, which is widely applied and economical, a relatively full-scale research is preceded. A new voltage and reactive power control design is proposed, which is suitable for the requirement of power system, reliable, owned perfect function and easy to be configured and be extended. The SIMATIC S7-226 Programmable Logic Controller (PLC) is selected as the master unit, which is strong in anti-jamming ability, abundant in instructions, has lots of expansion modules and excellent communication function. The operation parameters detecting unit is possessed of high reliability and can satisfy the need of the developing power system, which is an intelligent electric power parameters converter with communication function. The master unit communicates with the detecting units to gain the operation parameters, at the same time it can communicate with upper computer or other serial devices. The new control rules think well of those factors, which have obvious effect on the control results and the control method, is based on real-time calculation. So that this method is precise and can avoid the capacitor's oscillatory putting in and out and decrease the regulating times of tap changers. The program takes a decision according to the control rules. At the same time it can identify the system operation mode, make the capacitors putting in and out in order, protect the capacitors and the tap changers and bring communication into execution. The methods of high voltage switches, series reactance and the connation of shunt capacitors' choice are given out. The principle of tap change under load is also interpreted in this paper.Theoretic analysis and the results of simulation calculating show this control method is precise and easy to be carried out. The test shows that the design is advanced, flexible, reliable and strong in function, which can accord with the requirement of power system automation to control unit.