Reliability-Oriented Networking Planning for Meshed VSC-HVDC Grids

This paper proposes a reliability-oriented planning method to design reliable topologies for meshed high-voltage direct-current (HVdc) grids. Based on the proposed steady-state model for HVdc grids, a bi-level and multiobjective planning problem is formulated. The optimization model not only regards reliability as an independent objective, but also takes the power flow controllers (PFCs) into account. Compared with conventional methods, it overcomes the curse of dimensionality and solves the optimal allocation of PFCs. Then, the nondominated sorting genetic algorithm II is employed to solve the upper-level problem. For lower-level problems, an algorithm based on minimum spanning trees is proposed to optimally allocate PFCs, and an improved least frequently used cache algorithm and an optimum-test algorithm are developed to promote the computing efficiency of reliability evaluation. The European Supergrid and a Chinese ultra-HVdc system are adopted as test systems to validate the proposed method. Case studies prove that the proposed method provides an effective tool for the planning of HVdc grids. Also, results show that the cache technique and the optimum-test algorithm can reduce more than 70% of the total elapsed time.