Impact of Multilevel Inverter Supply on Losses in Permanent Magnet Synchronous Machines Considering High-Frequency Current Components

For inverter-fed permanent magnet synchronous machines (PMSMs), current harmonics significantly increase losses compared to ideal sinusoidal excitation, necessitating accurate modeling across all operating conditions. This type of simulation is not an easy task due to expensive computations, but it is indispensable. This paper uses a new approach for predicting losses in PMSMs driven by multilevel inverters (MLIs) with different switching frequencies compared to conventional two-level (2L) inverters. The proposed model incorporates actual current waveforms to capture high-frequency components responsible for PWM-induced losses. Core and magnet losses are evaluated for 2L and three-level (3L) inverters to demonstrate the advantages of MLIs in reducing these losses. PMSM losses are analyzed across different torque-speed operating points and decomposed into core, magnet, and copper losses, while inverter efficiencies for different topologies are also calculated. Results show that the 3L T-type inverter improves the PMSM driving cycle efficiency from 94.66% to 96.13% compared to the 2L inverter, demonstrating its effectiveness in minimizing PWM-induced losses. Additionally, the driving cycle efficiency of the traction system improves from 94.29% to 95.84%.