Efficiency Optimization of Electric Drives with Variable Switching Frequency using Wide-Bandgap Motor Drives

Abstract

Abstract The quest for increased energy efficiency for electrified vehicle propulsion systems has led to the adoption of fast-switching Wide Band Gap (WBG) motor drives. As research continues to focus on improving energy efficiency, the necessity arises to construct entire model, conduct co-simulation and analyze the power losses for these drive systems. The proposed work in this thesis presents a comprehensive investigation into the overall efficiency of an electric drive system, employed by variable switching frequency for sinusoidal pulse-width modulation (SPWM) over selected operating conditions. Utilizing ANSYS software tools, a drive system model containing an interior permanent magnet synchronous machine (IPMSM), a 3-phase inverter circuit, and a control system are developed. A preliminary study is carried out to compare the finite element analysis simulation with numerical calculations of the fundamental losses in the IPMSM when subjected to a sinusoidal power supply. The results illustrate the different control strategies that can be implemented, with the maximum torque per ampere (MTPA) method identified as ideal for the analysis. The process is subsequently repeated where the power is supplied through an SPWMcontrolled 3-phase inverter operating under the same set of conditions. The invertermotor losses are obtained for different switching frequencies at each tested operating point in the speed-torque envelope. The total energy efficiency of the inverter circuit and motor is determined for each operating point and corresponding switching frequency. Finally, the analysis produces an optimal switching frequency map, identifying the most efficient configuration for the entire drive system.