Research on Harmonic Mitigation Strategy of Static VAR Generator Based on Frequency Adaptation

Abstract

Offshore wind farms are integrated into the power grid via AC submarine cables, which may cause severe harmonic problems and reduce the power quality of the grid. To address the problem of excessive harmonics in offshore wind power plants (WPPs), this paper proposes a method applying the static var generator (SVG) with frequency adaptive harmonic mitigation function to the offshore WPPs. Firstly, the SVG model and the mechanism of harmonic mitigation are investigated. Secondly, the proportional and resonant control strategy is proposed according to the internal model theorem and applied to the voltage control loop of SVG. The harmonic suppression performance of SVG is studied through the Bode diagram. Thirdly, to adapt to the uncertainty of harmonic frequencies, the recursive least-squares method is introduced to realize the real-time tracking of harmonic frequencies. And the harmonic compensation bandwidth of the SVG is broadened by adjusting the parameters of the controller. Finally, the offshore WPPs in Jiangsu are built based on the Matlab/Simulink platform to verify the effectiveness of the mitigation strategy. Compared with the LC filter, the improved method can effectively mitigate (inter-) harmonics and has strong robustness and adaptability.