Assessment and Mitigation of Multi-Mode Oscillations in Wind-Solar Hybrid Multi-Microgrids

Multi-microgrids (MMGs) provide an effective solution for further improving the overall economy and ensuring resilience under major disasters, while high penetration level of renewable energy generations inevitably brings adverse oscillation problems to the system. So far, no comprehensive study has been carried out to assess the interaction and oscillatory stability of autonomous wind-solar hybrid MMGs. Besides, the feasible method giving consideration to coordinated control and simple communication architecture for damping out the multi-mode oscillations deserves further research. Therefore, this paper first establishes a detailed model of wind-solar hybrid MMGs by taking multiple types of renewable energy generations with similar and different response features in timescale into account, which are rarely included by most of the existing studies. Then, participation factor analysis is applied to reveal the multi-timescale interactions within the single microgrid and MMGs. Meanwhile, different critical influence factors, especially primary energy source fluctuations, are thoroughly investigated through sensitivity analysis to assess the multi-mode oscillations and stability issues. To mitigate the undesirable multi-mode oscillations, a hierarchical distributed damping controller based on the optimal partial output feedback technique is proposed subsequently. Finally, comparative tests are conducted to validate the correctness of the theoretical analysis and the effectiveness of the proposed method.