The unified power quality converter（UPQC） of modular multilevel converter（MMC） can be used for recovering power quality of voltage and current under high voltage

whereas it is difficult to comprehensively control the power quality when the voltage imbalance of the grid is remarkable. Therefore

the passive control method was applied to MMC-UPQC to solve the power quality problems under voltage imbalance. Firstly

based on the topological structure of MMC-UPQC

the mathematical model of MMC-UPQC was established under unbalanced power network. Secondly

the detection quantity was separated without phase-locked loop through a method of positive and negative sequence separation. Thirdly

based on the passive control theory

the PBC controller based on the E-L model was built and applied to power quality compensation system under multi-level and high-voltage. Finally

the principles of series side compensation voltage and parallel side compensation current were applied to the coordinated control for comprehensively solving the power quality problem of the grid under unbalanced state. The experimental results on the Matlab/Simulink platform show that the response time of the MMC-UPQC system based on the proposed passive controller is less than 0.05 s and the total harmonic distortion is less than 5%

which verifies the certain effectiveness and superiority in solving the problem of integrated power quality management.