The third-order PWA affine model of VSC-HVDC system is established. Aiming at the disadvantage of traditional MPC which needs rolling optimization, an EMPC method is proposed. The state space is convexly partitioned by multi-parameter quadratic programming, and a large number of on-line control calculation processes are transferred to the off-line stage for pre-calculation. In order to reduce the complexity of off-line calculation, the concept of separation function and offending point is introduced. By strictly separating saturated partitions, the number of partitions that need to be predicted and partitioned is reduced, and the speed of searching corresponding partitions for state variables in on-line calculation is indirectly accelerated. The control performance of EMPC is verified by simulation analysis under the environment of sudden load increase and system parameters change.