To suppress the influence of system disturbance on the DC voltage of flexible multi-state switch（FMSS）

an FMSS DC voltage control strategy based on an improved linear extended state observer（LESO） is proposed. Firstly

the DC voltage control outer loop is designed according to the DC voltage dynamic equation and the nonlinear relationship between the system variables. Then

the disturbance rejection scheme with feed-forward of the disturbance observation value is adopted

and an improved LESO for disturbance observation is proposed by selecting new error function and state variables. Finally

the disturbance feed-forward link is designed according to the DC voltage response function. The simulation results show that the DC voltage fluctuation of FMSS is reduced by 50% compared to using the conventional LESO

the settling time of the DC voltage is reduced by 13%

and the overshoot of the terminal output active power is reduced by 42%. Therefore

the strategy proposed in this paper can effectively suppress the influence of system disturbance on the DC voltage of FMSS.