Rooftop PV systems with distributed batteries for voltage unbalance mitigation in low voltage radial feeders

Abstract

This paper discusses the alleviation of voltage unbalance (VU) in low voltage four-wire ungrounded distribution networks. Unbalanced allocation of distributed rooftop Photovoltaic (PV) ratings and loads creates considerable neutral current in the neutral line. Because of the size limitation or non-connection of distributed batteries, this paper proposes three strategies for using the available distributed energy storage to reduce VU and neutral potential under a high penetration of distributed rooftop PVs. VU mitigation algorithms are presented and implemented in the MATLAB/software environment.

Review on voltage‐violation mitigation techniques of distribution networks with distributed rooftop PV systems

“…The strategy of cooperative ESSs along the distribution feeder is effective for VU mitigation. This strategy requires fewer currents and makes lower stress on ESSs but the communication link is mandatory [63].…”

Unbalance mitigation by optimal placement of static transfer switches in low voltage distribution feeders

“…The PVs beside the existing single‐phase loads and non‐symmetrical spacing between conductors can cause an unbalanced distribution feeder. The unbalance has several consequences such as deterioration in the performance and lifetime reduction of induction machines, reduction of the network efficiency due to more losses [2], service feeders tripping, security problems for line labours, overload in system equipment [3], reduction in the capacity of distribution transformers, and arising the circulating current and heat in the primary side of the star‐delta distribution transformers [4] to name just a few.…”

“…Energy storage systems and reactive power flow control of PVs have been proposed in some works for balancing purposes [2, 4, 9–16]. In [2], single‐phase storage systems installed in LV feeders have been charged/discharged to mitigate the voltage unbalance and network losses.…”

“…The main purpose of the work was focused on changing the output of a fixed‐location energy storage system to mitigate the voltage unbalance produced by the penetration of residential PV panels. Regulating the reactive power output of PV inverters has an effective impact on the balancing procedure of distribution networks [4, 9–13]. However, location, capacity, and hosting phase of installed residential PV panels are usually specified by the owners, and distribution system operators have no control over the parameters.…”

Voltage violation in four‐wire distribution networks integrated with rooftop PV systems

“…Additionally, the VU reduces the distributed transformers' capacities and the efficiency of many types of loads such as three-phase motors. Furthermore, it causes a large current in the neutral line which leads to high power losses and de-rating the feeder cable [1,2].…”