When the wind energy is separated from the power grid, explore to find a way by using four-leg active power filter to guarantee power quality to solve the problem caused by four-wire nonlinear load. Considering the disadvantage of phase locked loop, a real-time algorithm of detecting harmonic current based on improved i_p-i_q theory is proposed. The first step is to remove the zero sequence of the three phase current from the original current. And then in order to gain the compensation instructions of the harmonic current and zero sequence current and reactive current, using mean method of slide time window to get rid of the fundamental active current. And based on these steps, a dynamic and real-time simulation model is set up, under the environment of MATLABSIMULINK and the components of the libraries of SimPowSystems. Besides, the model of Fcn is used to program. The simulation results show that the detective algorithm of the harmonic current of nonlinear load is correct.
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