Risk Evaluation of Hybrid Microgrids Considering DC-Link Voltage Stability

This paper proposes a new risk assessment framework for hybrid microgrids design incorporating DC-link voltage stability issues of bidirectional voltage source converters. The dynamics of the ac side may lead to unstable operation of the dc-link voltage in rectifying mode. This problem will decrease the stability margin and limit the allowable power flow of converters in rectification mode. As a result, the overall reliability of the microgrid will be affected. Therefore, stability issues need to be taken into account within the planning and design of microgrids. Unlike the operation phase, where deterministic stability analyses are performed to ensure a secure operation of microgrids, in the design phase, the impact of stability on the overall system reliability needs to be modeled. The proposed method illustrates the impact of stability on the overall system risk thus facilitating stability-informed design optimization in microgrids. The effectiveness of the proposed method is verified through a hybrid microgrid (HMG) system considering a DC-link voltage instability issue. The risk assessment model is applicable for different stability challenges in future power electronic based power systems.