Abstract: An electromagnetic transient mathematical model of MMC based on switch state function was built and an improved MMC passive controller based on EL model was designed. The controller adopts error control method, namely using zero control error to make actual output track given reference value of MMC control system. In order to make error energy decay to zero rapidly and speed up dissipative characteristics, the damping matrix was introduced; To eliminate steady state residual voltage, MMC DC voltage was introduced to control system, and compared with reference direct voltage, the voltage is regulated by PI control and is added to active current reference component to get ultimate active current reference component. The simulation results show that the controller can completely track reference value, reduce voltage fluctuation range, and has good dynamic response.