Desigen And Research Of Combined Static Var Compensators

Along-standing problem In domestic power grid construction and operation is lack of var capacity and equipped with unreasonable, especially the adjustable var capacity used for voltage regulation and responding quickly reactive power equipments is insufficient. With the rapid development of power system, high pressure,ultra-high voltage grid has been put into operation, it needs high voltage and large capacity compensating devices, it’s one of the best mothed to steady system.Industrial electrical device, such as rolling mill, electric welding machine, electric arc furnace equipment of high power, are widely used in enterprises, which can have an important impact on power quality. Such loads, not only make the lighting flicker of incandescent lamp that make people feel uncomfortable, but also harm power supply normally for the other users connected in public power point, especially the electric arc furnace, connected in the system that has relatively small short circuit capacity, may cause the voltage fluctuation and three-phase voltage unbalanced.With the extended implementation of’West-East Power Transmission Project’ in China, Point-to-grid transmission, with high-capacity steam turbine and generator units, relatively high compensation level of series capacitor, becomes a common mode. However, this kind of transmission mode is prone to lead to the sub-synchronous resonance (SSR) problem caused by the generator shaft damage, which may cause generator shaft torsional vibration and even destruction, thereby endanger the safe operation of power systems. Therefore, the SSR of the system research is of great practical significance and value of engineering applications.In order to resolve these problems mentioned above, Static Var Compensation can be used in grid. Static Var Compensation device, compensated for grid, can rectify the power factor, reduce the loss of transformer and transmission line; compensated for loads, can restrain voltage fluctuation aroused by loads, compensate var current of loads, improve the power factor and repair unbalance of loads. The paper designs and studies a multi-objective controller for Combined Static Var Compensator in order to resolve voltage instability under large and small disturbance, voltage fluctuation caused by load, low power factor and negative sequence current,etc. The paper uses differential evolutionary and particle swarm optimization algorithm to set and optimize the related parameters of controller. At last, The paper design the additional damping controller of multi-channels and modes separation for SVC to regulate voltage, at the same time, suppress SSR of power system.