Ideally the power converters are supposed to be lossless. However in the real world there are many reasons that can cause power loss in the power converter system. Therefore minimizing the power loss and operating system at high efficiency point is an essential step towards developing optimized power conversion system. This thesis introduces a novel PWM control strategy - "Pulse-Width-Amplitude Modulation (PWAM)" method for HEV/EV motor or generator system. This modulation method is quite different from other PWM methods that have been well researched or commonly used for the inverter in HEV/EV system. By using this method, only one phase leg of the inverter is doing switching action at any time. Therefore, the inverter total switching time is reduced to one third comparing with conventional SPWM method and the total switching loss can be reduced by at least 50% or even more depending on the load condition (power factor). In addition, the inverter dc-link requires much smaller capacitor when PWAM method is applied, which makes the system smaller size and lighter weight. Simulation and experimental results are provided to verify inverter efficiency improvement.
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