Study on a Novel Multiport Electric Energy Router for AC-DC Hybrid Micro-grid using Active NPC with Decentralized MPC Algorithm

A 2 MVA three-port, i.e. 10 kV ac port, +5 kV dc port and ±1500 V dc port, electric energy router (EER) with single phase active ANPC structure of each terminal is introduced and developed. On-grid and islanded operation mode are discussed, in which decentralized model prediction control (MPC) method is mainly adopted. Compared with the traditional on- and off-grid research that only focuses on the control method of a single converter, this paper focuses on the overall coordinated control of each port. And comparative analysis between the traditional proportional integral (PI) control strategy and the MPC algorithm is conducted. The results indicate that the decentralized MPC performs better dynamic response which has a better effect on the realization of a fast on- and off-grid switching. And a novel on-grid and islanded mode phase synchronization unit is proposed. This synchronization unit uses the grid q-axis voltage to correct the phase of the EER to achieve stable synchronization. Simulation in Psim software shows decentralized MPC algorithm achieved better dynamic response while mode switching happened, and novel phase synchronization unit has a better continuity of the adjustment process compared with conventional method and synchronization parameters are easier to adjust.