基于虚拟额定电流的直流微电网分布式储能单元精确电流分配研究

Accurate Current Sharing of Distributed Energy Storage Units in DC Microgrid Based on Virtual Rated Current

为了孤岛直流微电网的稳定运行,通常需要配备储能系统。为了防止储能系统中部分分布式储能单元过充或过放,储能单元的荷电状态需要达到均衡状态。但不匹配线阻会不可避免地存在于实际直流微网中,并影响荷电状态均衡的效果。针对该问题,提出一种基于虚拟额定电流的策略,该策略基于常见的PI控制器就可消除线阻对荷电状态均衡的影响。基于上述策略,储能单元在充放电时可根据其荷电状态或放电深度自适应地调整虚拟阻抗,使荷电状态快速达到均衡。同时,采用电压恢复策略使直流母线电压恢复至电压参考值。此外,为了减轻对通信总线的压力,采用基于自律分散系统的分布式通信结构。此外,稳定性分析为所提控制策略提供了理论上的支撑。最后,基于RTDS平台的对比案例验证了所提控制策略的有效性。

Currently,energy storage system(ESS)is employed for stable operation of islanded DC microgrid.To prevent over-charging or over-discharging of certain distributed energy storage units(DESUs)in ESS,state of charge(SoC)need to be balanced.But mismatching between line resistances exists inevitably in DC microgrid and affects the effect of SoC balance.To solve the issue,a scheme based on virtual rated current is proposed in this paper.The scheme based on common PI controller can eliminate the impact of line resistances on SoC balance.Based on above scheme,DESUs can adjust the virtual resistance adaptively according to SoC or depth of discharge(DoD)during charging or discharging process,so that SoC can be balanced rapidly.Meanwhile,voltage recovery method is employed to control DC bus voltage to voltage reference.Besides,the distributed communication structure based on autonomous distributed system is adopted to reduce the pressure on communication bus.Additionally,stability analysis is performed to theoretically support the proposed control strategy.Finally,validity of the proposed control strategy is verified with comparative cases based on RTDS platform.