模块化多电平变换器(modular multilevel converter,MMC)是电池储能系统(battery energy storage systems,BESS)功率变换的最佳选择之一.在基于模块化多电平变换器的电池储能系统(MMC-BESS)运行时,会出现子模块之间的有功功率分布不平衡情况,为评估系统稳定安全运行的合理性,需要对子模块功率极限值进行分析.因此,该文首先对MMC-BESS建模,分析其桥臂环流的功率传输特性,再提出相应控制策略,包括外部交流及电池功率控制和内部电容电压平衡及环流控制,可以实现相间和桥臂间功率不平衡时的稳定运行,而对于桥臂内功率不平衡,根据安秒平衡原理,从过调制角度对子模块电池功率极限值进行详细分析,得出功率极限值的计算方法.最后,通过仿真以及实验验证功率极限值分析及计算的正确性.
Analysis of Power Limits for Submodule Batteries Based on MMC-BESS
Modular multilevel converter(MMC)is one of the best choices for power conversion in battery energy storage system(BESS).MMC-based battery energy storage systems(MMC-BESS)may face the challenge of imbalanced distribution of active power among submodules during operation.To assess the feasibility and safety of the system's stable operation,it is necessary to analyze the power limits of the submodules.Therefore,this article first models MMC-BESS,and analyzes the power transmission characteristics of its circulating current.Then,corresponding control strategies are proposed,including external power control and internal capacitor voltage balance and circulating current control,which can achieve stable operation when the power is unbalanced between phases and arms.For the power imbalance within the arm,the power limit of the submodule battery is analyzed in detail from the perspective of over-modulation according to the Ampere-Second balance principle,and the calculation method of the power limit is obtained.Finally,the correctness of the power limit analysis and calculation is verified through simulation and experimental verification.
modular multilevel converterbattery energy storage systemspower imbalancepower limitampere-second balance
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