Date of Award
Master of Science (MS)
Electrical and Computer Engineering
Electric vehicles are growing at a rapid pace in the internal combustion engine dominated transportation sector, and bring environmental and economic benefits to society. Electric vehicles produce nearly zero carbon emission, provided that they are charged through renewable energy sources. Electric vehicles reduce our dependency on foreign oil and also offer additional benefits like Vehicle-to-grid (V2G). V2G is a technology that allows electric energy stored in the electric vehicle batteries to be returned to the grid during peak demand. V2G can also provide voltage regulation, voltage shaving, reactive power compensation and distributed generation. This necessitates that an electric vehicle battery charger be bi-directional, capable of sinking or sourcing real and reactive power. The state of the art battery charging converter is unidirectional and has multiple stages of power conversion. In this thesis, a single phase, single stage, isolated, bi-directional Silicon Carbide (SiC) AC-DC converter based on Dual Active Bridge (DAB) topology is proposed and analyzed. Direct-quadrature axis (DQ) current control of the DABbased topology is implemented with phase shift modulation. Simulation results are presented with various operating conditions showing the converter’s ability to sink or source real and reactive power in the AC grid. Hardware and firmware implementation of a single phase bi-directional AC-DC converter operating at 100 kHz utilizing Silicon Carbide (SiC) MOSFETs are discussed in detail. Experimental results are shown confirming simulation results. A single phase bi-directional AC-DC converter uses large electrolytic capacitors to filter ripple currents in the DC bus. Electrolytic capacitors are bulky and are prone to failure. These electrolytic capacitors can be eliminated by rejecting the ripple current in the DC bus. The ripple current is rejected by injecting a current of same magnitude and opposite phase to the ripple current. A rigorous analysis is performed on the ripple rejection technique used in single phase bi-directional AC-DC converters. Simulation results are presented to verify the analysis. A three phase bi-directional AC-DC converter improves the charging time of the electric vehicles by charging the batteries at a higher power level. A three phase, single stage, isolated, bi-directional AC-DC converter is analyzed. DQ current control of the three phase AC-DC converter is implemented in simulation to verify the analysis.