| The power system is always unbalanced, so the negative sequence current having a frequency is twice as that of operating frequency, should be produced and enters the generator. When a disturbance happens, the operating frequency will be a little changed so that it can make the frequency of the negative sequence current hit the mechanical natural frequency of the turbine blades to create resonance, so-called supersynchronous resonance. Though the amount of the negative sequence current is usually not big, its resonant damage will be chronically accumulated to damage the generator.;This dissertation presents a feasible solution to protect a generator from this kind of resonant damage by using a special designed static var compensator (SVC) to reduce the negative sequence current. The verification of the fact that a three-phase reactive equipment such as SVC can balance the unbalanced real power is introduced. Before describing this specific SVC system as installed in the Power System Simulation Laboratory at the Energy System Research Center (ESRC) for actual field tests, the computer simulation for illustrating its influences on the whole power systems and the performance tests in a simulated power system are presented. This dissertation also describes the hardware electronic designs and the control algorithm. |
