Harmonic suppression mechanism analysis for wind power grid-connected converter and research on control strategy

In order to improve adaptability for wind power grid-connected converter under non-ideal grid conditions and reduce the harmonic influence, harmonic suppression mechanism for grid-connected converter is depth analyzed and harmonic suppression method and theory is derived. Be limited by complexity of the control system, compound control strategy composed by repetitive controller paralleled with PI controller is proposed for grid-connected converters control in this paper. System stability is analyzed, Geometric representation for repetitive controller stability is shown in figure and Control system difference equation is deduced. Using the proposed control strategy, no difference tracking current control is achieved in the fundamental positive sequence reference frame. The gird current harmonic can be effectively reduced and the converter grid adaptability is improved. The simulation and experimental results verified the effectiveness of the proposed control strategy.