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postgraduate thesis: An investigation into high efficiency, compact DC-DC power conversion systems

TitleAn investigation into high efficiency, compact DC-DC power conversion systems
Authors
Advisors
Advisor(s):Hui, SYRTan, SC
Issue Date2019
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Qin, Y. [秦亚霄]. (2019). An investigation into high efficiency, compact DC-DC power conversion systems. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR.
AbstractThis thesis presents a study on high efficiency, compact DC-DC power conversion systems for several DC/DC converter applications in DC microgrids. Firstly, a research study on high performance DC-DC power conversion systems in DC microgrids has been conducted. Specifically, design requirements and challenges have been highlighted based on different applications. It provides important design criteria for high performance DC-DC power conversion system design and guidance for further research directions. Secondly, for automotive lighting system, the LED drivers require special design considerations, which include voltage step-up and –down function, high energy efficiency and fast current reference tracking capability. Unlike the conventional efficiency improvement methods, which are based on cumbersome circuit/component optimization and/or modification for a single operating point, a simple approach based on topology transition is proposed, which can achieve a high efficiency for a wide input voltage range. In particular, the topology of the LED driver can change between buck, boost and buck-boost converter according to the level of the input voltage. In addition, a novel current mode controller is proposed such that (i) compatibility to different topologies (ii) seamless topology transition and (iii) fast current reference tracking can be concurrently achieved. The feasibilities of the proposed topology transition method and its control have been experimentally verified through a four-switch buck-boost converter prototype. It is shown that there is more than 5% efficiency improvement as compared to the conventional four-switch buck-boost converter. Then, for the renewable energy DC/DC power conversion, a new class of high-voltage-gain DC-DC converters for high efficiency and transformer-less DC-DC applications where large voltage step-up ratios are required, is presented in this thesis. It features high step-up voltage conversion ratio with a moderate duty cycle; non-pulsating input current; low voltage stress on all of the switches; easy implementation of control and driving circuits; and low cost due to reduced components via combination of a two-stage converter into a single-stage converter. A 300 W prototype of a 19-time converter achieving the peak efficiency of 96.1% is built. Both simulation and experimental results validating the theoretical analysis and operation of the converter are provided. Finally, for the DC/DC power conversion in data center applications, a new class of high frequency high-voltage-gain DC-DC converters for high efficiency and transformer-less DC-DC applications where large voltage step-down ratios are required, is presented in this thesis. The converter is derived from the hybrid integration of a switched-capacitor converter and a buck converter. It features high step-down voltage conversion ratio with a moderate duty cycle; low voltage stress on all of the switches; scalability for high current high-power applications; and low cost. Full soft-charging operation and minimal device voltage stresses are achieved under all operating conditions. Steady-state operations of the converter are comprehensively analyzed. A 900 W prototype of a 20-time converter achieving the peak efficiency of 92.5% with 1MHz switching frequency is built. The theoretical analysis and operation of the converter have been experimentally verified.
DegreeDoctor of Philosophy
SubjectMicrogrids (Smart power grids)
DC-to-DC converters
Dept/ProgramElectrical and Electronic Engineering
Persistent Identifierhttp://hdl.handle.net/10722/287093

 

DC FieldValueLanguage
dc.contributor.advisorHui, SYR-
dc.contributor.advisorTan, SC-
dc.contributor.authorQin, Yaxiao-
dc.contributor.author秦亚霄-
dc.date.accessioned2020-09-18T03:01:24Z-
dc.date.available2020-09-18T03:01:24Z-
dc.date.issued2019-
dc.identifier.citationQin, Y. [秦亚霄]. (2019). An investigation into high efficiency, compact DC-DC power conversion systems. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR.-
dc.identifier.urihttp://hdl.handle.net/10722/287093-
dc.description.abstractThis thesis presents a study on high efficiency, compact DC-DC power conversion systems for several DC/DC converter applications in DC microgrids. Firstly, a research study on high performance DC-DC power conversion systems in DC microgrids has been conducted. Specifically, design requirements and challenges have been highlighted based on different applications. It provides important design criteria for high performance DC-DC power conversion system design and guidance for further research directions. Secondly, for automotive lighting system, the LED drivers require special design considerations, which include voltage step-up and –down function, high energy efficiency and fast current reference tracking capability. Unlike the conventional efficiency improvement methods, which are based on cumbersome circuit/component optimization and/or modification for a single operating point, a simple approach based on topology transition is proposed, which can achieve a high efficiency for a wide input voltage range. In particular, the topology of the LED driver can change between buck, boost and buck-boost converter according to the level of the input voltage. In addition, a novel current mode controller is proposed such that (i) compatibility to different topologies (ii) seamless topology transition and (iii) fast current reference tracking can be concurrently achieved. The feasibilities of the proposed topology transition method and its control have been experimentally verified through a four-switch buck-boost converter prototype. It is shown that there is more than 5% efficiency improvement as compared to the conventional four-switch buck-boost converter. Then, for the renewable energy DC/DC power conversion, a new class of high-voltage-gain DC-DC converters for high efficiency and transformer-less DC-DC applications where large voltage step-up ratios are required, is presented in this thesis. It features high step-up voltage conversion ratio with a moderate duty cycle; non-pulsating input current; low voltage stress on all of the switches; easy implementation of control and driving circuits; and low cost due to reduced components via combination of a two-stage converter into a single-stage converter. A 300 W prototype of a 19-time converter achieving the peak efficiency of 96.1% is built. Both simulation and experimental results validating the theoretical analysis and operation of the converter are provided. Finally, for the DC/DC power conversion in data center applications, a new class of high frequency high-voltage-gain DC-DC converters for high efficiency and transformer-less DC-DC applications where large voltage step-down ratios are required, is presented in this thesis. The converter is derived from the hybrid integration of a switched-capacitor converter and a buck converter. It features high step-down voltage conversion ratio with a moderate duty cycle; low voltage stress on all of the switches; scalability for high current high-power applications; and low cost. Full soft-charging operation and minimal device voltage stresses are achieved under all operating conditions. Steady-state operations of the converter are comprehensively analyzed. A 900 W prototype of a 20-time converter achieving the peak efficiency of 92.5% with 1MHz switching frequency is built. The theoretical analysis and operation of the converter have been experimentally verified. -
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.rightsThis work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.-
dc.subject.lcshMicrogrids (Smart power grids)-
dc.subject.lcshDC-to-DC converters-
dc.titleAn investigation into high efficiency, compact DC-DC power conversion systems-
dc.typePG_Thesis-
dc.description.thesisnameDoctor of Philosophy-
dc.description.thesislevelDoctoral-
dc.description.thesisdisciplineElectrical and Electronic Engineering-
dc.description.naturepublished_or_final_version-
dc.date.hkucongregation2019-
dc.identifier.mmsid991044168856203414-

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