Feasibility Analysis on Energy Balance of Doubly-Fed Wind Power Systems Under Grounding Faults

The paper introduces the energy imbalance problems of doubly-fed induction generator(DFIG) under grid faults, which occurs between the input energy of the wind turbine and the output energy of DFIG connected to the power grid. No literature has covered them yet until present. The output energy of DFIG is related to the excitation control strategy of rotor side converter. Firstly, an analysis is made on the output active power of DFIG under existing excitation control strategies, which shows that the DFIG electromechanical energy balance cannot be achieved under the existing excitation control strategy. Then, based on an analysis on the relation between the output active power of DFIG and the three major factors of rotor current, including the amplitude, frequency and phase of rotor current, the rotor current command is deduced to achieve the electromechanical energy balance of DFIG. A simulation circuit system is developed by using Matlab/Simulink, which verifies the correctness of the above deduction process.