The output characteristics of the inverter are easily affected by the load, and unbalanced load will cause three-phase output voltages unbalance of the inverter. In order to solve the problem of voltage unbalance, the Dual Quasi-Proportional Complex Integral (DQPCI) controller is proposed in this paper. The DQPCI controller can not only control the steady-state error of the AC signal in a small range, but also effectively suppress voltage unbalance components. Firstly, based on the mathematical model of the four-leg inverter, the control principle of the inverter and working characteristics of the DQPCI controller are analyzed in αb0 stationary frame. Secondly, based on the mathematical models and electric circuit models of the quasi-proportional resonant controller, quasi-proportional complex integral controller and dual quasi-proportional complex integral controller, the similarities and differences of working performances among the three controllers are compared and analyzed. In addition, the influences of controller parameters and the load on the system performance are analyzed by the bode diagrams, and the design and verification of the parameters are also carried out under no-load condition. Finally, simulative results with PSCAD verify the correctness and validity of the proposed control strategy. This work is supported by Beijing Municipal Natural science Foundation (No. 3172036).