Research On Flexible Topology Of DC-DC Converters

The universality and versatility of the Power Electronics Standard Power Module (PESPM) is the second objective of the research of Power Electronics System Integration (PESI), after the first objective of standardization of the power modules had being successfully completed. It plays a substantial key role to assure the PESPM being applied prosperously in the practical applications and posing a major support to boost the power electronics industry. The technique of Variable Topology Flexible Converter (VTFC) is exactly the very embodiment of the universality and versatility of the PESPM. With the concept of VTFC, this thesis carries out a extensively research in the area of: soft-switching optimization of the topologies with functional isomorphism, soft-switching optimization of the bidirectional DC-DC converters which suit for the concept of VTFC, theories of topology isomorphism and duality, topology seeking of the VTFC, constitution of shifting circuitry of the VTFC, shifting control strategy, topology and circuit components compatibility, as well as the main constitution paradigms and applications of the VTFC, and proposes broad and entire theories which is highly applicable and aiming for improve the universality and versatility of the PESPM. The summary of the proposed theories is the basic system and research framework of the VTFC, which can be recognized as an instruction on how to improve the universality and versatility of the PESPM.The main stream of the power electronics remains the topology research. Based on the situation that the optimized topologies proposed in the former PESI research have the weakness of lacking of a universal optimizing methodology, this thesis proposes the concept of functional isomorphism, according to the similarities and differences between the PESI candidate topologies. Then, the universal optimizing methodology was proposed based upon the power rating of the candidate topologies with characteristic of functional isomorphism. The methodology of topology researching with topology functional isomorphism can reveal a series topologies related to the original one and extend the area of PESI candidate topology. Furthermore, the study of a specific topology is looking forward to acquire a breakthrough on an expected characteristic. The research results show the proposed methodology of topology researching of topology functional isomorphism is effective and productive. The bidirectional DC-DC converter with an equivalent electric stress for the corresponding power switches in both power flows is researched, the methodology on how to judge and how to realize the ZCS for the rectifiers was also proposed. Based on the proposed theories, a topology family with 24 elements, where every element can achieve ZCS for the rectifiers was proposed. Moreover, a bidirectional topology family with 24 elements, where every element can achieve ZVS for chopping switches and ZCS for rectifier switches was proposed, which means the switching loss is minimized and these topologies realize a double-soft-switching. These double-soft-switching bidirectional DC-DC converters can be recognized as the VTFC, and the prototype verifies their excellent performance. Meanwhile, the topology seeking process and operation mode shifting strategy can also be taken as reference when the research comes to the VTFC. Besides, the research of the double-soft-switching bidirectional DC-DC converters strongly assures the theory and techniques of the VTFC in the area of DC-DC converters can be successfully established and applied in the area of the AC converters.From the previously research results, this thesis discusses the 3 main features of the special VTFC, performs the research on the constitution theory of the special VTFC when applied in the wide input range applications. The relation of isomorphism and duality between the sub-topologies of the special VTFC was investigated, which means the special VTFC should be formed by isomorphism and duality topologies. The existence of a minimum number shifting devices was proved and an algorithm based on the transforming matrices was proposed. A universal shifting control strategy by energy-consuming method was proposed and the corresponding sub-mode shifting logical state machine was generated. In order to get compatible for the converter small signal, two solutions, which can be expressed as the digital control method and the feedback compensating method, were proposed. Contrastively, turn-ratio shifting method and frequency tuning method were proposed to assure the compatibility of the magnetic components. Two prototypes of the special VTFC not only verify the 3 main features of the special VTFC and its correctness, but also instruct how to build a good performance but low cost special VTFC.The characteristic of non-reuse of the circuit components and being much more flexible in constitution and shifting are stated after the general VTFC and special VTFC were compared. The 3 main features of the general VTFC were discussed, and the 3 major constitution paradigms, including 7 sub-paradigms were also systematically concluded and analyzed. By the one-to-on case study of each sub-paradigm, it is well shown that the proposal of constitution paradigms of the general VTFC can reflect the latest trend of the universality study of the power modules and navigate the development trend of the power electronics. The two general VTFC verifies the 3 main features and the correctness of the general VTFC. Furthermore they also illustrate the broad extent of the application of theory of the general VTFC and its applicable value.