Study On Control Strategy Of Secondary Voltage Control

Alone with the development of power grid and the problem of voltage stability, more and more attention has been focused on coordinated automatic voltage /var control. Secondary voltage control is an effective way to improve the power system's voltage level and enhance voltage stability, and it has been used in many countries.In secondary voltage control scheme, the whole power system is divided into several almost uncoupled zones, and"Pilot Nodes"are selected for each zone. During on-line operation, secondary voltage controllers monitor the voltage magnitude of the pilot nodes and update the reference values of controllers at primary level, trying to maintain the voltage profile throughout the whole control zone within desired limits.Until now, the Secondary voltage control has gone through two development stages. The first is stage is the decentralized secondary voltage control (DSVC) applied only in system consisting of several mutually independent compact zones, it applies a proportional- integral law to determine signal. And now it has been developed to Coordinated Secondary Voltage Control (CSVC). It takes into account the system limits, in closed-loop mode, it compute fresh set-point values for generator primary unit controls. The paper proposes the main principle of CSVC, studies the control strategy, proves the validity and feasibility by simulate on to several systems.(1) Studies the control strategy of DSVC, improved a secondary voltage controller, designed a BP ANN based secondary voltage controller, and simulation results show that the proposed design controller is effective in voltage control.(2) Studies the control strategy of CSVC, analyzed the CSVC frame and its objective functions, Studies the principles of the multi-agent based secondary voltage control system and the coordination of CSVC and load shedding, to improve CSVC in emergency modes. At last, the paper addresses the active-set method to solve the optimization of a quadratic function.Simulation results show that CSVC is more effective than DSVC.