Analysis of Multi-level Inverters for Electric Vehicle Application
Examensarbete för masterexamen
Electric power engineering (MPEPO), MSc
Seshadri, Manoj Krishna
Abstract Traditional two-level inverters are used for electric vehicles on the market today. But, in recent years there is a growing interest in multi-level inverters to be used as the propulsion inverter in electric vehicles. So, this thesis work analyzes the performance of a multi-level inverter of different topologies as a traction inverter and a comparison is made with a traditional two-level inverter. Using a multi-level inverter, multiple levels of the output voltage can be obtained which helps in the reduction of losses and also THD. The implementation and analysis of this work are mostly carried out in PLECS software where different topologies of the multi-level inverter are modeled, simulated and the comparison between the different topologies is made in various aspects such as losses, THD, and also the DC link ripple from the capacitors. The thermal analysis is also done as the inverter models are designed considering the thermal properties of the power module. Finally, a comparison of the different topologies is made using two different switches. One uses the SiC switch and the other uses the GaN switch. In this thesis, a two-level inverter and a multi-level inverter of three levels are in vestigated. In a multi-level inverter, four different topologies (i.e., Neutral point clamped inverter, T-type neutral point clamped inverter, Flying capacitor inverter, and Cascaded H-bridge inverter) are modeled, simulated, and analyzed. Two differ ent switching strategies (i.e., Sine wave PWM and Space vector PWM) are imple mented for the inverter models. But for the multi-level inverter models, phase-shifted sine wave PWM is used. As the number of levels increases, the complexity of the modulation technique, cost, and size of the inverter increases. So, when it comes to selecting an inverter, it is a trade-off between all the above parameters.