Benchmarking study of Voltage and Current Source Inverter for Integrated Modular Motor Drives

Abstract

With the adoption of Wide Band-gap (WBG) switches in Integrated Modular Motor Drives (IMMDs), the size of the drive is rapidly reduced with increase in efficiency and thermal performance. But with the advantages, use of WBG switches as a direct replacement for Si IGBT/MOSFET in Voltage Source Inverter (VSI) posses challenges in the field of steep dv /dt which leads to problems like over-voltage at motor terminal, degradation of cable and motor insulation leading to bearing current and EMI problems.
Current Source Inverter (CSI) mitigates the problems associated with WBG usage in VSI but involves additional components like series SiC diodes leading to additional losses and temperature. This thesis explores design of VSI and CSI topology for High Speed Permanent Motor (HiSPEM) IMMD applications conducts bench-marking study of VSI an CSI based on efficiency and thermal performance of converters. .
To begin with, VSI topology for IMMD modelled in PLECS with designing of control strategy. The loss model of SiC MOSFET used in VSI is simulated along with a lookup-table loss model for fast thermal performance evaluation. The current response is verified with the experimental setup with the comparison of loss model and thermal model results.
Subsequently, the CSI topology is modelled with designing of multi-loop control strategy. The decoupling of the D and Q axis is performed using feed-forward decoupling method. The calculation of output capacitor filter is performed based on the cutoff frequency. The stability and bandwidth of different controller in the multi-loop are evaluated using bode plot analysis. Later, the diode loss is modelled and a thermal model is constructed using loss lookup-table for both SiC MOSFETs and series SiC didoes.
The VSI and CSI typologies are bench-marked against each other on parameters such as converter loss, efficiency and thermal performance revealing the optimum topology to use at different current ratings and switching frequencies.