Abstract
Due to rapid progress of power electronics technology and power semiconductor devices, it is now possible to achieve a much better performance for various power converters. In this dissertation, the research topic is focused on the AC/DC boost converters with bi-directional power flow and with variable power factor. Owing to the fast response, easy implementation and with bounded errors for achieving a specified power quality, the conventional hysteresis current controller has been developed and widely used for long time. However, there still exists some drawbacks for further improvement and some theoretical analysis about certain peculiar phenomenon remains to be clarified. Hence this dissertation, starting from satisfying the basic characteristics of the conventional hysteresis current controller, tries to provide a unified methodology for analyzing the controllers considered in this dissertation. In fact, while applying this methodology to the three-phase case, some peculiar phenomenon about various error-bound-violation cases are now clarified and fully understood for the first time. As a result, an improved three-phase error bounded current controller is proposed to guarantee the satisfaction of a specified error boundAnother important contribution of the dissertation lies in the application of zero mode control at the proper time to further reduce the switching numbers of the converters to achieve better efficiency and reliability. Sound theoretical basis is presented and detailed analysis is also made by using the unified methodology. Totally, four current controllers are proposed. Among them, two single-phase controllers with constant sampling period are inherently suitable for digital implementation. One is more suitable for lower output voltage applications and the other is more suitable for higher output voltage applications. The third single-phase hysteresis controller, instead of using constant sampling period, is however proposed to achieve the minimum switching frequency by using the unified methodology. Finally a three-phase controller is also proposed by extending the previous single-phase result. Due to the two dimensional considerations, this extension process is not a trivial one at all. It is worth pointing out here that, instead of using only the information of the current errors, the proposed controller uses also the information of the sign of the current error derivatives without incurring extra calculations. Hence, better controller performance can be achieved without requiring too much extra efforts. Some simulation and experimental results are also given for verifying the feasibility of the proposed controllers.