Impedance Shaping of Grid-Connected Converter Based on Gershgorin Disc Theorem and Return Ratio Matrix

With the large-scale grid connection of renewable energy, a series of oscillation problems have been aroused. Especially when the power grid is weak, the renewable energy controller is easy to interact with the grid. The common solution is to shape the converter impedance. The existing research often increases the margin of renewable energy devices to cope with the change of grid impedance. However, the regulation ability is limited and the verification of shaping results is not intuitive enough. According to the stability criterion based on Gershgorin disc theorem and the system return ratio matrix, this paper proposes a new index of impedance shaping, and the specific correction target of the converter impedance element is determined. Then the shaping is realized according to voltage feedforward at the point of common coupling. With this proposed method, the system stability is significantly improved, the influence of the grid is fully considered, and the measurement results can be directly used for analysis. Finally, simulation results verify the effectiveness of the proposed method.