Security-constrained AC-DC hybrid distribution system expansion planning with high penetration of renewable energy

With the increasing penetration of renewables into the AC-DC hybrid distribution system, it is necessary to develop a security-constrained planning approach to address the uncertainty brought by renewables. Motivated by the urgent need to accommodate high penetration of renewable energy resources in weak grids, this paper presents a novel planning approach for AC-DC hybrid distribution systems considering the N-1 security criterion. Network reconfiguration is incorporated as a method to improve the flexibility of the system under normal and post-contingency conditions. To alleviate the burden of computing all possible N-1 contingencies, a novel solving strategy with a nested loop structure is proposed. In the inner loop, a novel contingency screening method is designed for the fast identification of high-risk contingencies under a given planning solution. In the outer loop, the obtained high-risk contingency set is adopted to refine and filter the security constraints, so that the planning solution can be improved iteratively. The superiority and effectiveness of the proposed planning model and solving strategy are tested on a real-world distribution network in Zhejiang Province, China. Numerical results verify that the proposed planning approach is able to deal with the installation of large-scale renewable energy while ensuring the security of the system.