Due to production and manufacturing differences, the consistency of many lithium-ion batteries used in series and parallel will deteriorate, so battery equalization techniques are needed to maximize the available battery capacity and ensure safe battery pack operation [1–3].
Solar photovoltaic (PV) is considered a very promising technology, and PV-lithium-ion battery energy storage is widely used to obtain smoother power output. In this paper, we propose a battery equalization circuit and control strategy to improve the performance of lithium-ion batteries.
According to the voltage characteristic analysis of the lithium-ion battery, when the SOC>80% or the SOC<30%, the voltage consistency is poor. Therefore, it is necessary to turn on the active equalization control so that the battery pack can charge and discharge more power, and improve battery energy utilization.
There are many types of lithium-ion battery equalization circuits, the most common of which is the passive equalization circuit. The active equalization circuit is better than the passive equalization circuit in terms of performance, but it is very complex and expensive .
In pursuit of low-carbon life, renewable energy is widely used, accelerating the development of lithium-ion batteries. Battery equalization is a crucial technology for lithium-ion batteries, and a simple and reliable voltage-equalization control strategy is widely used because the battery terminal voltage is very easy to obtain.
The entire battery pack is divided into several modules to improve the equalization speed . This equalizer introduces intra- and inter-module equalization. In intra-module equalization, all the cells in a module are equalized as in a conventional equalizer. This equalizer allows module-to-module equalization.