A Two-stage Reactive Power Optimization Strategy for AC/DC Hybrid Distribution Network

To adapt to the integration of various types of distributed generations (DGs) and loads, AC/DC hybrid distribution network (ADHDN) has become an important branch of future distribution network. But the increasing penetration of DG has brought voltage regulation problem to the economic operation of ADHDN. In this paper, a two-stage reactive power optimization strategy for ADHDN based on unified power flow calculation is proposed, aiming at minimizing the comprehensive cost of ADHDN economic operation. In the first stage, the slow control measures such as open/closed status of switches in network reconfiguration and the tap position of on-load tap-changer (OLTC) transformer are determined before the day. In the second stage, the reactive power outputs of static var compensator (SVC), DG and voltage source converter (VSC) are optimized within the day. Based on second-order cone relaxation and multilayer piecewise linearization, the original mixed integer nonconvex nonlinear programming problem is transformed into a mixed integer second-order cone programming (MISOCP) problem. Finally, the modified IEEE 33-node system is used for simulation calculation, and the optimal results verify the effectiveness and practicability of the proposed strategy.