Analysis of low harmonics and high efficient BLDC motor drive system for automotive application

This project presents a comparative study of VSI, CSI and Buck Converter based CSI fed BLDC Motor for automotive applications. The aim of the work is to reduce the cost and size of a brushless dc motor (BLDC) drive as well as increase the reliability and ruggedness of the drive. Traditional BLDC drives use Voltage Source Inverter (VSI) that utilize hard switching, thereby generating switching losses and entail the use of large heat sinks. VSI needs a huge dc link capacitor that is inherently unreliable and is one of the most expensive components of the drive. Hence, a Current Source Inverter (CSI) is used to replace the hard switching by soft switching, thereby eliminating the heat sinks as well as the large dc link capacitor. A controlled rectifier together with a large inductor acts as a current source, the only disadvantage is the large value of the dc link inductor and the huge number of turns needed to achieve these values of the inductances lead to huge resistive losses. Therefore, it is shown that it is possible to replace the controller rectifier and the large inductor with a suitable Buck converter based current source inverter can be switched at high frequencies with much smaller value of the dc link inductor without increasing the current ripples. Hence, it is possible to have the advantage of using a CSI as well as reduce the value of the dc link inductor without a corresponding increase in the heat sink. The effectiveness of the VSI and CSI fed BLDC motor schemes are verified through the simulation results.