Optimal scheduling of voltage control resources in unbalanced three-phase distribution systems

This paper presents an optimal scheduling of tap changing transformers and converters interfaced with distributed generators (DGs) in unbalanced three phase distribution systems. Since the renewable energies are attracting worldwide attention, the DGs considered here are supposed based on photovoltaic (PV) generators. The unbalanced three phase power flow equations are solved using Newton Raphson method, and the three phase elements models are considered. The distribution losses are optimized whereas the system constraints include turns ratio of voltage transformers, the reactive power output of the DGs inverters, and the power flow equations using Genetic Algorithm (GA) method. The optimization is performed based on predicted values of load demand and PV generation, while maximizing the PV active power is considered. A one-day optimal schedule is generated for a 14-bus distribution system with three phase unbalanced load, and then used for 24 hours real time simulation to verify the effectiveness of the method. The simulation results show that all the constraints are satisfied based on the generated schedule.