Based on the harmonic apparent power defined by the IEEE 1459-2010 power standard, the paper proposed a new method of identifying the main harmonic source at the point of common coupling (PCC). Using the reference impedance method, the utility and customer harmonic voltage and current contributions are calculated. And then combined with the IEEE 1459-2010 standard, defined the harmonic apparent power caused by the independent action of the equivalent harmonic source on the system side and the user side, by directly comparing the size of the two to determine the location of the main harmonic source. The method can consider the comprehensive influence of harmonic voltage and harmonic current, then identify the main harmonic source at PCC point. Finally, the rationality of the method is verified by the simulation of the IEEE 13 node system.

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To explore the self-excitation risks in weak interconnection power grid from the wind power flow, a vector control model of variable speed wind turbine based on doubly fed induction generator (DFIG) is established using electromagnetic transient simulation software PSCAD/ EMTDC. Start from the basic circuit model, the self-excitation phenomenon is analyzed with wind power integration. Simulation results show that the effect of wind power integration on the self-excitation risk is mainly determined by DFIG’s operation method, and wind power integration will affect self-excitation engineering judgment method at the same time. When DFIG works in phase late operation or has no reactive power exchange with the main power grid, cutting the wind turbine after broken thread quickly can restrain the worsening trend to a certain extent. However cutting the wind turbine after broken thread when DFIG works in phase advance operation may cause a voltage jump of the hydraulic synchronous generator in parallel with the wind turbine.