A Three-level Coordinated Optimization Method to Regulate Voltage Variations in Distribution Networks with High Photovoltaic Power

This paper proposes a three-level voltage regulation method to mitigate voltage variations of distribution networks caused by active power fluctuations of photovoltaic (PV). In the first level, the leader-follower consensus algorithm (LFCA) is used to control the charging and discharging power of battery energy storage systems (BESSs) and the active power reduction of PV plants to limit the real-time (1min) voltage variation. A reactive power optimization model is established in the second level to optimize the short-term (5min) reactive output of each PV plant, aiming at the minimization of nodal voltage deviations. Meanwhile, it also considers the state of charge (SOC) correction of BESSs. In the third level, a model predictive control (MPC) based integer nonlinear programming (INP) model is developed to optimize the tap of the on-load tap changer (OLTC) and the reactive output of capacitor banks (CBs), which aims to cope with the voltage fluctuations caused by the long-term (30min) power changes in loads and PV plants. Simulation results indicate that the proposed methods can effectively control nodal voltage variations of a feeder within the pre-defined range by coordinating an OLTC, CBs, PV plants, and BESSs.