As a new type of power electronic device

flexible multi-state switch(FMSS)can partly replace the traditional tie switch in the distribution network to realize uninterrupted flexible regulation of power flow and optimize voltage profile. Several possible topologies and working modes of the three-port FMSS in the distribution network are discussed. The dynamic mathematical model of three-port FMSS is established and a three-port FMSS coordination control strategy based on finite-control-set model predictive control(FCS-MPC)is proposed

which has many advantages of clear principle

simple implementation and fast dynamic response. It avoids the problems of traditional propontional-integral(PI)double closed-loop control strategy including complex control structure

more PI parameters and difficult setting. Based on FCS-MPC

the control algorithms of UdcQ mode

PQ mode and Uacf mode are implemented. Accordingly

the coordination control strategy between the modes of three ports is presented. In order to verify the feasibility of the proposed scheme

a three-port FMSS simulation model is built by using MATLAB/Simulink. Simulation results show that the proposed coordination control strategy can effectively achieve multi-port coordinated control and adjustment function which can provide a flexible solution for the applications of multi-port FMSS.