Efficiency, Cost and Volume Comparison of Si-IGBT Based T-NPC and 2-Level SiC-MOSFET Based Topology with dv/dt Filter for High Speed Drives

The high frequency operation of the WBG devices such as SiC emphasizes the effect of parasitics, generating the reflected wave phenomenon and transient overvoltage on motor terminals, reducing the life time and the reliability of electric drives. In this paper the efficiency comparison of two topologies has been considered, a SiC-MOSFET based two-level and Si-IGBT based three-level T-NPC inverter. The goal was to have the fair comparison, having the same output voltage capabilities and same output current THD. T-NPC inverter is considered without an output filter, meeting the standard on voltage stress, while the dv/dt filter of 2L-SiC based inverter is designed to meet the same specification as that of the T-NPC inverter. The two inverters are considered with fastest switching and minimal losses. The efficiency comparison indicated the convenience of using SiC MOSFET-based 2L inverter with an dv/dt filter for lower output power, while Si-IGBT T-NPC inverter shows higher efficiency for higher output power. The T-NPC inverter shows the lowest cost and total volume as well. The goal was to ease the decision process and to have the clearest picture possible when comes to the judicious choice of the practitioners in the motor drive industry. Simulations were carried out by realistic dynamic models of power devices obtained from the manufacturer's experimental tests and verified both in the LTspice and PLECS simulation packages.