Real-time volt/var optimization for distribution systems with photovoltaic integration

This paper presents a two-stage optimization approach to mitigate the rapid voltage fluctuations and minimize the power losses of distribution systems due to the high penetration of photovoltaic (PV) generation. The first stage is a day-ahead optimal strategy which aims to minimize the total voltage deviations and power losses within the constraints of the daily maximum allowable number of operations of the on-load tap changers (OLTCs) and shunt capacitors (SCs). The second stage is a real-time inverter reactive power control to compensate for the uncertainties of PV output and load demand. As a part of the real-time control, an artificial neural network (ANN) approach is used to estimate the system states. In both stages, the optimization problems are formulated as nonlinear optimization problems and solved with direct search algorithms. The real-time optimization method is tested using a Hardware-In-the-Loop (HIL) simulation platform. A modified IEEE 34-node test feeder is applied to demonstrate the effectiveness of the proposed approach.