Development of advanced power factor correction techniques

Three novel power factor correction (PFC) techniques are developed for both single-phase and three-phase applications. These techniques have advantages over the conventional approaches with regard to the converter efficiency, power density, cost, and reliability for many applications.

The single-phase parallel PFC (PPFC) technique was established. Different from the conventional two-cascade-stage scheme, the PPFC technique allows 68% of input power to go to the output through only one time high frequency power conversion, but still achieves both unity power factor and tight output regulation. A family of PPFC converters were proposed for different power levels, which are simpler and more efficient than the conventional two-cascade-stage systems. Since isolated boost converters are adopted as the main power stage in some of the PPFC converters, a device based soft-switching technique was proposed for using IGBTs as the main power switches, which ensures the lower cost and higher efficiency benefits of the PPFC technique.

The single-ended boost converter is the most frequently used converter in the single-phase PFC applications. For high power and/or high voltage applications, the major concerns of the conventional boost converter are the inductor volume and weight, and Iosses on the power devices, which will affect converter efficiency, power density, and cost. In this dissertation, a novel three-level boost converter was developed, which can use a much smaller inductor and lower voltage devices than the conventional one, yielding higher power density, higher efficiency, and lower cost.

In three-phase applications, the three-phase boost rectifier is the most popular topology for the PFC purpose. A novel high performance boost PFC rectifier was developed, which provides several superior features than the conventional one with nearly no cost increase. lt inherently provides six-step PWM operation, which is the optimal PWM scheme with no circulating energy, minimum input ripple current, and minimum . switching events. It also greatly reduces the bridge diode reverse recovery loss, which is one of the major switching Iosses in the conventional three-phase boost rectifier. Furthermore, it can adopt very simple soft-switching techniques even with three independent analog controllers to further improve the performance. Several simple soft switched three-phase boost rectifiers have been developed. Besides, the bridge shoot-through problem is virtually eliminated. As a result, these new three-phase boost rectifiers have higher efficiency, higher power density, lower cost, and higher reliability compared with the conventional one.