基于模块化多电平直流变换器的储能系统分布式能量均衡控制策略

Distributed Energy Balancing Control Strategy for Energy Storage System Based on Modular Multilevel DC-DC Converter

为了解决级联式储能系统中储能模组间能量均衡问题,同时提升系统的模块化程度,提出一种分布式能量均衡控制策略。该策略充分利用了双向直流变换器模块化结构的特点,将各子模块采用独立闭环控制。为了使子模组能够独立进行能量均衡,将下垂控制思想以及超级电容荷电状态(SOC)引入到电流闭环中,使子模组能够根据自身SOC状态调整工作电流,进而实现能量自动分布调整,达到均衡控制目的。为了减小模组SOC对系统电流的影响,控制策略中引入了电流校正环节,从而改善系统电流的调整率。该策略不影响储能系统稳定母线电压的能力,同时各储能模组间不需要任何通信,使系统具备了完全的模块化特性。最后,通过实验验证了所提方法的有效性。

In order to settle the energy balancing issue between energy storage modules and improve the modularity of the cascade storage energy storage system,this paper proposes a distributed energy balancing control strategy.Independent voltage and current closed loops are built in the strategy by making full use of the DC converter modular structure characteristics.For the purpose of making sub-modules balance energy independently,droop control ideology and state of charge(SOC)are adopted in the redesigned current loop.Thus,the sub-module can adjust the operating current according to its SOC,and then realize the automatic adjustment of energy distribution to achieve the purpose of balancing control.In order to reduce the effect of SOC on system current,current correction unit is introduced to improve the current regulation.This strategy has no influence on the ability of ESS to stabilize the DC bus voltage and does not require any communication between modules,so that the system owns complete modular features.At last,the experimental results have verified the proposed strategy.