A simple and easy-to-implement battery equalization strategy for photovoltaic-battery energy storage systems

For renewable energy sources such as photovoltaic (PV), energy storage systems should be prioritized as they smooth the output well. Although lithium-ion battery energy storage systems are favored for their excellent performance, the large number of batteries connected in series and parallel may lead to inconsistent battery packs, which can cause system problems. Therefore, battery equalization techniques should be employed. This article proposes a battery equalization technique suitable for PV battery energy storage systems. In terms of the equalization circuit, we propose an equalization circuit consisting of a switch-selective circuit and a Cuk circuit, which is simple and easy to expand; in terms of the equalization strategy, we adopt a highly robust fuzzy logic control to better adapt to PV battery energy storage systems, we developed a set of control rules suitable for this equalization strategy. We have investigated the principle of the proposed battery equalization technique and verified it experimentally during the battery pack's resting, charging, and discharging. The consistency of the battery pack is significantly improved as a result.