Static Security Risk Assessment for Islanded Hybrid AC/DC Microgrid

Due to the lack of the support from the main grid, the islanded hybrid ac/dc microgrid will more likely cause the power flow severe fluctuation and even the microgrid to be split once a serious contingency occurs. To maintain the security and stability of the system under such a condition, this paper proposes a new static security risk assessment of the islanded hybrid ac/dc microgrid considering that the hybrid ac/dc microgrid was split. First, this paper presents a static security analysis criterion to determine the post-contingencies splitting scheme and a new load-shedding strategy to achieve power balance of subsystems. On this basis, a probabilistic power flow calculation method based on Levenberg-Marquardt with a nonmonotone line search (LMNL) algorithm is applied to calculate the probabilistic power flow of the islanded subsystems. Finally, the probability distribution of static security risk assessment indexes, including the dc loss load risk, ac loss load risk, and interlinking converter (ILC) active power limit violation risk, are obtained. The simulation results on the test system demonstrate the necessity of considering the hybrid ac/dc microgrid was split, and prove the feasibility and effectiveness of the proposed method.