Performance Analysis of Switching Table Based DTC for 5-Phase Induction Motor with 3-Level Inverter

Abstract

When leg and level of an inverter are increased, the number of switching states increases cumulatively. When the switching table-based DTC with higher phase (leg) and level is implemented for multiphase induction motor, the switching table becomes more accurate for different types of loading. Here, a 5-phase induction motor is simulated in MATLAB/Simulink from its dynamic mathematical equations. The switching table based direct torque control (ST-DTC) has been implemented to the simulated model through a 5-leg 3-level inverter. A performance study for ST-DTC has been carried out among 5-phase induction motor using 2-level (FPIM 2-L) inverter, 5-phase induction motor using 3-level (FPIM 3-L) inverter and 3-phase induction motor with 3-level (TPIM 3-L) inverter, and results are compared. In FPIM 3-L inverter, out of 243 switching states 20 active switching vectors are chosen for preparation of switching table, whereas in TPIM 3-L inverter, out of 27 switching states 12 switching vectors are chosen. In FPIM 2-L inverter, ten are chosen out of 32 switching states for DTC application. As the active states are increased, the numbers of sectors are also increased for FPIM 3-L inverter. With FPIM 3-L inverter, there is an improvement in settling time during step fall. The torque ripple in case of FPIM 3-L inverter is reduced by 4.18% with respect to FPIM 2-L and 2.7% with respect to TPIM 3-L inverter. However, the torque response during start is slightly sluggish in case of FPIM 3-L inverter as compared to TPIM 3-L inverter.