Analysis on Mechanism of Inter-Area Forced Oscillation Caused by Local Weak Interconnection in Interconnected Power Grid

By use of the theory of multiple-degree-of-freedom(MDOF) systems and eigenvalue analysis,the mechanism of inter-area forced oscillation in interconnected power grid brought out by local weak interconnection is researched.According to current features of power gird interconnection in China,it is pointed out that the underdamped local oscillation is the potential menace to system stable operation.The relation between multi-machine forced oscillation and system natural oscillation frequency and that between multi-machine forced oscillation and correction factors of generation units are emphatically anlayzed.It is proposed that if following conditions are satisfied,i.e.,the oscillation frequency of perturbance source is close to that of inter-area oscillation mode and there is strong correlativity between locally oscillated units and inter-area oscillation mode,the inter-area forced low frequency oscillation will be caused to happen.Finally,based on the data recorded by wide area measurement system(WAMS),two forced low-frequency oscillation faults in Central China Power Grid are analysed using the proposed mechanism,and analysis results show that the proposed mechanism is rational and correct.