Current rating analysis of a nine-switch based unified expandable power converter considering different configurations

Using low switch converters due to their cost-effectiveness has been an interesting topic in different applications such as grid integration of distributed generation systems and multi-machine drives. Recently, a nine-switch based unified expandable power converter (UEPC) has been presented for integration of multi permanent magnet synchronous machine (PMSG) based wind energy systems (WESs) in which the number of switches in comparison with the conventional configurations is significantly reduced. Nevertheless, since all switches are shared between all ports and therefore, the currents of different ports pass through all switches, the current rating of the switches might be higher than the conventional structure. In this paper, to minimize the total required current rating of the semiconductor as well as the installation cost of the UEPC, different acceptable configurations considering different port for grid connection are evaluated and the best port for grid connection is proposed. Finally, to verify the analysis results, the simulation of a three-port version of UEPC is carried out using MATLAB/Simulink software. The simulation results also confirm that when the grid is connected to the middle port, the minimum instantaneous currents pass through the switches.