Multi-objective Particle Swarm Optimization-Based Placement and Sizing of Distributed Generators Integrated to Unbalanced Low-Voltage Microgrids by Four-Leg Inverters

Determining the best position and rating of distributed generators (DG) is crucial for a microgrid’s planning and operation. Their improper placement and sizing may lead to the degradation of many network metrics. Unequal distribution of loads/sources across the three phases leads to voltage imbalances in low-voltage microgrids. When power system equipment is fed with an unbalanced voltage, both its performance and its life may suffer, necessitating correction. The voltage imbalances can be corrected by feeding negative-sequence current using converters with four legs. Therefore, if the DGs are integrated into the microgrid by four-leg inverters, both the task of feeding power and correcting voltage unbalances can be done simultaneously. In this paper, a multi-objective particle swarm optimization (MOPSO)-based method is proposed for determining the ideal position and rating of DGs connected to a low-voltage unbalanced microgrid by four-leg inverters. There are two objectives: the first is to determine the positions and ratings of DGs for which the real power distribution loss is minimum, and the second is to determine the locations at which the total voltage unbalances in the microgrid are at their lowest. The optimization is obtained using two approaches: first, a weighted factor-based MOPSO is used to obtain a unique solution based on the priorities assigned to each objective. Secondly, a Pareto-based MOPSO is used to obtain all the non-dominated alternatives from which a specific solution may be chosen based on preference. Two unbalanced radial distribution systems are used to implement the proposed method. The results demonstrate that it is possible to determine the ideal DG ratings and positions for a maximum reduction in voltage unbalances and distribution losses using the proposed method. © 2023, The Institution of Engineers (India).