Theory and Experiences of SVC for Damping Subsynchronous Resonance

Both the theory and the experiences of Static Var Compensator for damping the subsynchronous resonance are investigated in this paper. Firstly,the basic operation principle of the static var compensator to damp the subsynchronous resonance is analyzed.The major component of the static var compensator for damping the subsynchronous resonance usually consists of a deltaconnected three-phase thyristor-controlled reactor.The analysis of the principle shows that damp of the subsynchronous resonance can be achieved by modulating the reactive current in the thyristor-controlled reactors.Then,based on the basic principle,various control strategies of the static var compensator for damping the subcynchronous resonance,such as the proportional controller,the modal control technique and the voltage controller etc,are presented respectively.And the structure of each type of controller is shown in detail.Further,a method of estimating the size of the static var compensator is introduced and a corresponding example based on the IEEE first benchmark model is also presented.Secondly,based on the Tuoketuo power plant,the effects of the static var compensator on damping the subsynchronous resonance are simulated and analyzed in time domain by the program PSCAD/EMTDC.And the simulation results show that the static var compensator can damp the subsynchronous resonance effectively with a simple proportional controller.The results are helpful to solving the subsynchronous resonance problems which exist in the series compensated transmission systems in China.And the conclusions also provide valuable references for better applications of the static var compensators.