Analysis and design of computationally efficient modulation schemes for Three Phase Three Switch rectifier for transportation electrification

Abstract

It is a well-known fact that the transportation sector emits a large amount of pollutants to the atmosphere. The growing need for reducing the carbon footprint has led to sincere efforts being made in the direction of electrification of commercial vehicles, which conventionally run on by-products of crude oil. The Canadian government is currently aiming at reducing greenhouse emissions by 30% below the early 2000s levels by the year 2030. This goal has led to major auto manufacturers releasing their respective models of battery-powered electric vehicles (EVs) completely compliant with the SAE J1772 standards. However, the commercial success of EVs heavily relies on the presence of high-efficiency charging stations. This thesis reviews presently available, Level 3/DC fast charging systems, followed by a brief description and evaluation of DC fast-charging infrastructure. Different power converter topologies and viable configurations are presented, compared, and evaluated, based on the power level requirements, efficiency of the topology, cost, and technical specifications. In this thesis the possibility of employing the Three Phase Three Switch (TPTS) converter as a single-stage charger for DC fast charging of electric vehicles is explored. Control of contemporary three phase power converters, employed in charging infrastructures, is achieved by Space Vector (SV) based modulation schemes. This thesis proposes a novel modulation technique for TPTS rectifier. The general SV modulation scheme xxvii xxviii used to control the TPTS is reviewed in this thesis. Numerous switching combinations possible for different positions of the Zero and Active vectors are derived. Based on the positions of these vectors in different sectors of the SV diagram, several switching sequences are presented. The switching combinations are analyzed to obtain three modulating waves. The new carrier-based modulation scheme for TPTS is implemented and validated using software simulation. This new scheme is easier to implement compared to the traditional SV based modulation technique due to reduced number of mathematical computations. A 1 kW hardware prototype was built to validate the proposed modulation scheme. This thesis provides a detailed description about arriving at the proposed modulation scheme for TPTS from traditional SV modulation scheme. The implementation of the converter and its performance analysis is reported in this thesis