A control scheme for voltage unbalance mitigation in distribution network with rooftop PV systems based on distributed batteries

Abstract Unbalanced loads create unacceptable voltage unbalance (VU) in low voltage (LV) three-phase four-wire distribution networks with unbalanced rooftop photovoltaic (PV) systems. This paper proposes a mitigation strategy for restricting the VU depending on the distributed batteries that included in grid interfaced rooftop PV systems. Moreover, it introduces a dynamic control model based on two PI-controllers for determining the required batteries’ compensating currents and ensuring equality resultant stress current on each bus. It overcomes three existing challenges; the inequality stresses currents on the distributed batteries along the feeder, the insufficient size or non-existing of the distributed batteries, and satisfies the same stress among batteries on the same bus. For investigating the influence of equal phase magnitude batteries’ compensating current at the same bus on the whole distribution network (DN). Particle Swarm Optimization (PSO) and Bat optimization techniques are used to determine the optimum self and mutual sharing co-efficients of each battery. The limits of the distributed batteries' size are taken into consideration in the optimization process. The proposed dynamic model is implemented using MATLAB software. The simulation results show the effectiveness of the proposed control scheme for mitigating the VU on the distribution feeder’s buses at three scenarios; different loads, PVs, and states of charge of batteries. Moreover, the batteries’ compensating currents are presented to examine the implementation feasibility.