Abstract

In recent times, the demand for high voltage and high current rating motor drives for electric vehicles applications has increased. These conditions place a great deal of stress on the semiconductor switches, which are usually based on silicon. Multilevel converters provide an alternative that reduces the stress on the switch and also improves the quality of the voltage output. On the other hand, 2-level power converters have proven to be reliable over a number of years. Therefore, they have been used as building blocks to achieve higher voltage and/or currents, by creating a multilevel effect to improve the quality of the voltage waveforms supplied to the motor. In this project, a power configuration with dual 2-level inverters supplying an Open End Winding Machine (OEWM) was studied.
This thesis investigates the Space Vector Modulation (SVM) switching strategy for an open end winding machine, fed by dual 2-level inverters. One DC voltage source is employed to feed the both inverters. In addition, the problem of Common Mode Voltage (CMV) in this configuration was discussed in depth and the cause of this problem was explored.
The existing SVM strategy to eliminate the CMV due to switching states was discussed in depth and it was modified in order to eliminate the effect of dead-time on the common mode voltages. The existing modulation strategy was adjusted to re-align the switching states according to the phase current direction in order to obtain a proper sequence. The proposed scheme is also applicable for n-level inverters.
The performance of the system under the proposed strategy in terms of current and voltage quality was investigated and duly presented. The studies were conducted in MATLAB/Simulink software in the time-domain. Loss calculation using PLECS toolbox is also provided in this thesis.