A two-stage equalization control method for a delta-connected cascaded energy storage system

Abstract

The invention provides a triangle connection cascade energy storage system two stage equalization control method. The method comprises the steps that 1, SOC and SOH information of each link of a chained energy storage system is acquired; 2, rechargeable power and dischargeable power of each link are respectively calculated; 3, total rechargeable power and dischargeable power of each line and the whole system are calculated; 4, power distribution and control are carried out on each line; and 5, on the basis that the power of each line is determined, the voltage of each link is distributed according to the proportion of the rechargeable / dischargeable power of each link, and power distribution according to the proportion can be realized. According to the invention, the maximization of the capacity utilization rate of the energy storage system is used as a goal, namely simultaneous complete charging and discharging are carried out on batteries of all links; a safe operation boundary is considered, so that the requirement of the energy storage system for an equalization ability in different operation conditions and SOC states can be reasonably reflected; and an equalization performance is optimized in a range which can be realized.

Description

technical field [0001] The invention relates to an energy storage system equalization control method, in particular to a two-stage SOC equalization method applied to a triangular cascaded energy storage system, which is used in large-capacity battery energy storage occasions. It belongs to the field of battery energy storage. Background technique [0002] The cascaded energy storage system has attracted increasing attention due to its modular structure, high voltage, low current, low current harmonics and high efficiency under the same power. The control of the three lines of the cascaded energy storage system connected in a delta connection is decoupled from each other, and its control method is simpler than that in a star connection. This topology also has a two-level balancing function for the battery. [0003] At present, there are not many studies on the equilibrium control of cascaded energy storage systems at home and abroad. In 2008, Japanese scholar Akagi et al. p...

AI Technical Summary

Problems solved by technology

This control strategy with the direct goal of eliminating SOC deviation is simple and easy to understand, but it also has the following shortcomings: 1) It is suitable for the static balance of the energy storage system. For the energy storage system in dynamic operation, this control strategy does not consider the balance capability Link to Overall Charge and Discharge Time

2) Does not consider the actual runtime SOC security boundary

The current control method that only considers the size of the SOC deviation cannot reflect the difference in control under the above conditions

3) Factors that do not consider the capacity difference of batteries in the same energy storage system

The control based solely on SOC and SOC deviation may lead to repeated forward and reverse equalization of batteries with small capacity during the one-way charging or discharging process of the energy storage system, which increases the burden of equalization and reduces efficiency.

4) More importantly, for delta-connected cascaded energy storage systems, since there is no physical "phase", the zero-sequence voltage injection method is no longer applicable to the balanced control of energy storage systems

Images