Using Wide Bandgap Semiconductors to Develop High Performance Inverters in Electric Vehicles

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This project falls within the EPSRC Electrical motors and drives and electromagnetics research area.This project is funded through the Industrial CASE award, with the industrial partner being YASA Limited.Research ContextWith the global market shares of electrified and electric vehicles predicted to almost triple between the years 2020 and 2025, the role of electric powered vehicles in the automotive industry is increasing at an astonishing rate. Although the global demand for electric vehicles is increasing, solutions to the various problems that are present with their design need to be addressed. Among these problems, one of the key bottlenecks is the range of an electric vehicle. To increase the distance per kWh, there are multiple systems that can be looked at, with one of them being the inverter. Improvements in the performance of the inverter can considerably increase the range of an electric vehicle.One of the key future developments in the improvement of electric vehicle inverters is the use of wide bandgap semiconductors. The higher thermal conductivities and operating frequency of wide bandgap semiconductors also play a role in their preference in electric vehicle inverters. This project will aim to develop ways of utilising the beneficial properties of wide bandgap semiconductors, to improve performance of electric vehicle inverters.Primary Research Aims and ObjectivesThe objective of the research will be to design and test new circuit designs, which utilise the properties of wide bandgap semiconductors to their advantage. This concept will be proved over a number of tests, designed to simulate the load of an electric motor in a vehicle.Proposed MethodologyAn extensive literature review will be carried out, studying current modern inverters and how their structures and function depend on the properties of IGBTs, specifically the constraints created by them and how these influenced the design of the inverters. Further study of wide bandgapsemiconductors and their properties will be done, also emphasising their limitations, as these will be different from IGBTs and so will pose different design problems. Research into other possible wide bandgap semiconductors, other that the conventional ones of GaN and SiC, could yield semiconductors with more useful properties in the context of this problem.Next, the most common inverter structures will be examined to find the core concepts they use in their functionality and how these are influenced by practical limitations of the components in the circuit, so as to help gauge how the benefit of using wide bandgap semiconductors can be maximised, when standing in for IGBTs in the current inverter circuits.Once wide bandgap semiconductors have been incorporated into current inverter structures, the circuits can be reassessed for limitations is their performance, due to other components in the circuit and the general circuit structure. From there, new circuit structures can be devised to properly utilise wide bandgap semiconductors and their beneficial characteristics.After new inverter circuits have been proposed, these can be tested against current inverters, when under a load which properly simulates a vehicle motor under use. This will not only help to test the efficiency of the new inverter circuits against existing one, but aid in checking the circuits' functionality under non-standard test loads, i.e. the durability of the circuits when not just driving a motor at a constant speed and torque.