模块化多电平储能复合变换器SOC均衡策略研究

Research on SOC equalization strategy of modular multilevel energy storage hybrid converter

以物理结构及功能上高度集成为目标的模块化多电平变复合变换器(modular multilevel hybrid converter,MMHC)电池储能系统(battery energy storage system,BESS)可以直接并入中、低压交流电网,相较于其他电池储能系统具有效率更高、成本更低的优点,有利于解决分布式新能源发电侧出力的间歇性和不确定性问题,实现用户侧负荷的削峰填谷。根据MMHC-BESS拓扑结构特点,给出了MHHC-BESS的调制策略,针对多电平变换器电池储能系统中电池组采用安时积分法配合开路电压法对电池荷电状态(state of charge,SOC)估计效果差的问题及MMHC-BESS能量利用率的问题,分别提出了基于扩展卡尔曼的电池模型闭环SOC估计策略及二层SOC均衡策略,实现了MMHC-BESS所有电池组SOC的精确估计及MMHC-BESS的相间、相内所有电池组模块SOC均衡,并搭建了仿真模型,验证了所提SOC估计方法及均衡策略的有效性。

The modular multilevel hybrid converter(MMHC)battery energy storage system(BESS)with the goal of high integration in physical structure and function can be directly integrated into the medium and low voltage AC grid,which has higher efficiency and lower cost than other battery energy storage systems.The advantages of this are conducive to solving the intermittent and uncertain problems of the output of the distributed new energy generation side and realizing the peak-shaving and valley-filling of the user-side load.Based on the characteristics of the MMHCBESS topology,the modulation strategy of MHHC-BESS is given.Aiming at the problem of poor estimation of the state of charge(SOC)of the battery using the ampere-hour integration method and the open circuit voltage method for the battery pack in the multi-level converter battery energy storage system,and the problem of the energy utilization rate of MMHC-BESS,respectively.A closed-loop SOC estimation strategy and a two-layer SOC equalization strategy based on the extended Kalman battery model are proposed,which realizes the accurate estimation of the SOC of all battery packs in MMHC-BESS and the SOC balance of all battery pack modules in phases and phases of MMHC-BESS.A simulation model is used to verify the effectiveness of the proposed SOC estimation method and equilibrium strategy.