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实际工程中,模块化多电平变换器(modular multilevel converter,MMC)上、下桥臂参数不可避免地会存在一定的差异,从而导致交流侧电流中出现直流和2倍频分量,直流侧电流中出现基频和2倍频振荡分量,以及不同桥臂间电容电压发生不平衡等一系列问题.为解决这些问题,建立了桥臂参数不对称情况下MMC的解耦控制模型,提出了桥臂电流直接控制策略,有效地改善了参数不对称下MMC的电流控制问题.同时,基于子模块级联串能量模型,提出一种有功环流和无功环流相结合的环流注入方法,在实现上、下桥臂电容电压平衡的同时,确保MMC的端口特性不受内部环流的影响.最后,仿真和实验结果验证了理论分析和所提控制策略的有效性.“,”The upper and lower arm parameters of modular multilevel converters (MMCs) have some differences inevitably in the practical projects. Under this asymmetric condition, the dc current and double-frequency current will flow into the AC side, the fundamental circulating current will flow into the DC side and the capacitor voltage imbalance will occur among different arms. To solve these problems, the decoupled control model of MMC under asymmetric conditions was established, the arm current direct control strategy was then proposed in order to improve the performance of current control of MMC under asymmetric conditions. Meanwhile, based on the energy model of the cascaded sub-modules, a circulating current injection method with the combination of active and reactive circulating currents was proposed, which can achieve capacitor voltage balance between upper and lower arms and keep the terminal characteristic of MMC unaffected by the internal circulating current. Finally, simulation and experimental results verify the effectiveness of the theoretical analysis and the proposed control strategy.