A three-phase inverter circuit using half-bridge cells and T-NPC for medium-voltage applications

Abstract

Three-phase single DC-source based multilevel inverter topologies play a piv otal role in industrial applications due to the reduced number of components and higher efficiency. This paper emphasizes the inverter for medium-voltage applications that employ a conventional three-phase T-type structure (T-NPC). The primary circuit of the proposed configuration consists of a T-NPC struc ture connected to the half-bridge cells at the top and the bottom sides of each phase. The secondary circuit consists of DC-link capacitors whose voltage balancing is attained through a separate voltage balancing circuit (VBC). Using the proposed configuration, the number of components and independent DC supplies are reduced compared with the conventional topologies such as a neu tral point clamped (NPC) inverter, a flying capacitor (FC) inverter, and a cas caded H-bridge (CHB) inverter for the same number of output voltage levels. Hence, the proposed topology results in the reduction of weight, volume, and power losses of the inverter. A sine-triangle comparison method is employed in the field programmable gate array (FPGA) platform to generate the firing pulses of the circuit switches. The effectiveness of the proposed topology is ver ified with simulation studies and is experimentally validated with a scaled down prototype