Performance Improvement Of Electric Driveline Using Modulation Techniques

Abstract

Abstract This thesis work will study different modulation techniques and their effects on the system losses of a traction motor and inverter for automotive applications. The machine, inverter and total system losses are simulated and analyzed for Space Vector Pulse Width Modulation (SVPWM), Active Zero State Pulse Width Modulation (AZSPWM), Near State Pulse Width Modulation (NSPWM) and Discontinuous Pulse Width Modulation (DPWM) techniques across the torque-speed map at 10 and 15kHz switching frequencies. Motor losses are estimated using current fed simulations to a FEM model in JMAG. These current injections are generated using a custom closed loop coupled analysis, performed using a 2-D partial derivative model of a permanent magnet synchronous machine (PMSM), a 3-phase inverter circuit with speed, torque and current control and a custom modulator block in MATLAB/ Simulink. Inverter losses are on the other hand estimated using a numerical approach on MATLAB. The result of this study is an optimal modulation map where Hybrid DPWM techniques outperform SVPWM over a majority of the torque speed map, by a discernible margin for this studies model. This work, will also discuss the methodology and implementation of different DPWM techniques, along with their efficacy across different power factors, and the resultant reasoning and logic devised to develop a custom Hybrid DPWM technique optimized for efficiency. The variations of AZSVPWM, its logic and limitations, as well as that of NSPWM, with its loss maps and THD maps are also discussed and presented.