Isolated Multi-Input Converters With Single Primary Winding

Renewable energy is one of an effective solution for solving the energy crisis problems and the environmental pollutions. However, the renewable energy has some disadvantages such as intermittence and and variation with climate conditions, and it cannot provide continuous power to the load. So, it is better to combine several renewable energy sources together, and a hybrid renewable energy power system is constructed. In such hybrid renewable energy power system, each renewable energy source needs a dc-dc converter, and the system configuration is very complex. Recently, the concept of multiple-input converter (MIC) is proposed to replace the multiple dc-dc converters, leading to a simplified system configuration, less device numbers and lower cost. This dissertation is dedicated to the isolated MIC circuit topologies and control strategies.In the past, the synthesization of MIC topologies based on the concept of pulsating source cells, including pulsating voltage source cells (PVSCs) and pulsating current source cells (PCSCs), have been proposed, and some non-isolated and isolated MICs have been derived. However, the derived isolated MIC is somewhat complicated. In this dissertation, multiple pulsating source cells are connected in series or parallel, and then replace the input voltage source of single-input converter, as a consequence, a family of isolated single primary winding (SPW) MICs is proposed. The control strategies for the isolated SPW MICs are proposed, and the characteristics of isolated SPW MICs are analyzed. Compared to the isolated MIC with several primary windings, the proposed isolated SPW MIC features simpler transformer structure, lower switch device stress, and all the power sources can power the load independantly or simultaneously.The flyback converter is widely used in low-medium power conversion applications due to its simple structure and electrical isolation. In this dissertation, taking as the example, the operation principle of the double-input flyback SPW converter is analyzed, and the voltage conversion is derived as well as the voltage and current stress of switches. The power management and control strategy for the double-input flyback SPW converter is proposed to fully utilize the renewable energy. A 120 W prototype is built and tested in the lab, and the experimental results are given to verify the theoretical analysis of the double-input flyback SPW converter.The full-bridge converter is suitable for high-medium power conversion applications. The isolated voltage-fed and current-fed full-bridge SPW MICs are proposed in this dissertation. As an example, the operation principle of the isolated double-input voltage-fed full-bridge SPW converter is analyzed. The effects of the switching sequence of the switches of the PVSCs and the mother converter on the filter inductor current ripple are analyzed, and it is revealed that the switching sequence of the mother converter has no effect on the filter inductor current ripple, but the switching sequence of the switches of the PVSCs has great effect on the filter inductor current ripple. In order to minimize the filter inductor current ripple, an interleaved dual-edge modulation for the switches in PSVCs is proposed. Furthermore, the power switches of the mother converter are let to switch at the time instance of one of the clock signals for the power switches of the PVSCs. With such arrangement, the power switches of the mother converter can realize zero-voltage-switching (ZVS) with the use of the resonant inductor (including the leakage inductor of the transformer) and the junction capacitor of the switches. An 800 W prototype is built and tested in the lab, and the experimental results are presented to verify the theoretical analysis.