4 research outputs found

    Analysis and design of a dual series-resonant DC-DC converter

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    DC-DC conversion systems are vital components in DC distribution systems, renewable energy generation systems, telecommunication systems, and portable electronics devices. The extensive applications of DC-DC converter have resulted in continuous improvement in the topologies and control methods in these converters. The challenge is to build a converter that improves factors such as efficiency of conversion and power density with a simple topology, which incorporates simplified switching and control schemes and fewer numbers of active and passive components to reduce the manufacturing cost. This thesis addresses this challenge by proposing an alternative topology of a DC-DC converter based on dual series-resonant circuits. The proposed topology operates under zero voltage switching (ZVS) and zero current switching (ZCS) conditions to reduce the switching losses. It achieves two degrees of freedom (i.e., duty ratio and switching frequency) to control the output voltage of the converter, which results in both step-down and step-up voltage conversions. The number of active components is limited to two semiconductor switches and two rectifying diodes, which reduces the manufacturing cost of the converter. Detailed analytical analysis is carried out using the extended describing function methodology to characterize the steady state and small signal operation of the converter. Small-signal transfer functions are developed and used to propose a simple closed-loop control scheme to control the output voltage of the converter. An experimental 10 V, 40 W prototype of the proposed converter is built and tested to investigate its operation and confirm its features. The improvement in the efficiency of the converter and power transfer capability of the proposed dual series-resonant converter compared with the traditional single series-resonant circuit, which is used in the interleaved topologies are experimentally verified. In addition, soft switching operation of the converter is realized and a simple control scheme is developed to control the output voltage of the converter. A detailed and step-by-step design procedure is developed, which can be used to customize the design of the converter for different levels of power and voltage. It is shown that the proposed dual series-resonant DC-DC converter provides significant improvement regarding power density, efficiency of power conversion, simplicity of switching and control schemes, and reduced number of converter components resulting in a low cost and compact converter

    High gain non-isolated DC-DC converter topologies for energy conversion systems

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    PhD ThesisEmerging applications driven by low voltage level power sources, such as photovoltaics, batteries and fuel cells require static power converters for appropriate energy conversion and conditioning to supply the requirements of the load system. Increasingly, for applications such as grid connected inverters, uninterruptible power supplies (UPS), and electric vehicles (EV), the performance of a high efficiency high static gain power converter is of critical importance to the overall system. Theoretically, the conventional boost and buck-boost converters are the simplest non-isolated topologies for voltage step-up. However, these converters typically operate under extreme duty ratio, and severe output diode reverse recovery related losses to achieve high voltage gain. This thesis presents derivation, analysis and design issues of advanced high step-up topologies with coupled inductor and voltage gain extension cell. The proposed innovative solution can achieve significant performance improvement compared to the recently proposed state of the art topologies. Two unique topologies employing coupled inductor and voltage gain extension cell are proposed. Power converters utilising coupled inductors traditionally require a clamp circuit to limit the switch voltage excursion. Firstly, a simple low-cost, high step-up converters employing active and passive clamp scheme is proposed. Performance comparison of the clamps circuits shows that the active clamp solution can achieve higher efficiency over the passive solution. Secondly, the primary detriment of increasing the power level of a coupled inductor based converters is high current ripple due to coupled inductor operation. It is normal to interleaved DC-DC converters to share the input current, minimize the current ripple and increase the power density. This thesis presents an input parallel output series converter integrating coupled inductors and switched capacitor demonstrating high static gain. Steady state analysis of the converter is presented to determine the power flow equations. Dynamic analysis is performed to design a closed loop controller to regulate the output voltage of the interleaved converter. The design procedure of the high step-up converters is explained, simulation and experimental results of the laboratory prototypes are presented. The experimental results obtained via a 250 W single phase converter and that of a 500 W interleaved converter prototypes; validate both the theory and operational characteristics of each power converter.Petroleum Technology Development Fund (PTDF) Nigeri

    μ „λ₯˜ 증배 μ •λ₯˜νšŒλ‘œλ₯Ό μ‚¬μš©ν•œ λŠ₯동 ν΄λž¨ν”„ ν¬μ›Œλ“œ μ»¨λ²„ν„°μ˜ μ˜μ „μ•• μŠ€μœ„μΉ­μ— λŒ€ν•œ 뢄석과 섀계

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    ν•™μœ„λ…Όλ¬Έ (석사)-- μ„œμšΈλŒ€ν•™κ΅ λŒ€ν•™μ› : 전기곡학뢀, 2014. 2. μ‘°λ³΄ν˜•.디지털 λΆ€ν•˜μ˜ 폭발적인 μˆ˜μš” μ¦κ°€λ‘œ 인해 높은 효율의 전원곡급 μž₯μΉ˜κ°€ μš”κ΅¬λœλ‹€. 디지털 λΆ€ν•˜λ“€μ˜ 주된 λ™μž‘ μ˜μ—­μ€ κ²½λΆ€ν•˜ μ˜μ—­μ΄λ―€λ‘œ 이런 μž₯비에 전원을 κ³΅κΈ‰ν•˜λŠ” μž₯μΉ˜λŠ” κ²½λΆ€ν•˜ 효율이 맀우 μ€‘μš”ν•˜λ‹€. κ²½λΆ€ν•˜ 효율 κ°μ†Œμ˜ 주된 원인은 μŠ€μœ„μΉ­ 손싀이닀. 이것을 κ°œμ„ ν•˜κΈ° μœ„ν•΄ λ³Έ λ…Όλ¬Έμ—μ„œλŠ” μ „λ₯˜ 증배 μ •λ₯˜νšŒλ‘œκ°€ μ‚¬μš©λœ λŠ₯동 ν΄λž¨ν”„ ν¬μ›Œλ“œ μ»¨λ²„ν„°μ˜ μ˜μ „μ•• μŠ€μœ„μΉ­ 쑰건을 λΆ„μ„ν•˜κ³  그에 ν•©λ‹Ήν•œ 섀계 κ°€μ΄λ“œλΌμΈμ„ μ œμ‹œν•œλ‹€. 일반적인 λŠ₯동 ν΄λž¨ν”„ ν¬μ›Œλ“œ μ»¨λ²„ν„°λŠ” μž‘μ€ μžν™” 인덕터λ₯Ό μ‚¬μš©ν•˜μ—¬ μ˜μ „μ•• μŠ€μœ„μΉ­μ„ μ–»λŠ”λ° μ΄λŠ” 1μ°¨λ‹¨μ˜ 도톡손싀을 μ¦κ°€μ‹œν‚€λŠ” 단점이 μ‘΄μž¬ν•œλ‹€. 반면 μ „λ₯˜ 증배 μ •λ₯˜νšŒλ‘œκ°€ μ‚¬μš©λœ 이 νšŒλ‘œλŠ” κ²½λΆ€ν•˜ μƒν™©μ—μ„œ μ˜μ „μ•• μŠ€μœ„μΉ­μ„ μ–»κΈ° μœ„ν•΄ λΆ€μ‘±ν•œ μ—λ„ˆμ§€λ₯Ό 2차단 좜λ ₯ 인덕터에 흐λ₯΄λŠ” μ „λ₯˜λ‘œλΆ€ν„° μΆ©λ‹Ή λ°›μ•„ μ˜μ „μ•• μŠ€μœ„μΉ­μ„ μˆ˜ν–‰ν•¨μœΌλ‘œμ¨ κ²½λΆ€ν•˜ νš¨μœ¨μ„ κ°œμ„ ν•œλ‹€. λ³Έ 회둜의 μ˜μ „μ•• μŠ€μœ„μΉ­μ˜ 과정을 μ„€λͺ…ν•˜κΈ° μœ„ν•΄ κ·Έ 쑰건을 λΆ„μ„ν•˜κ³  λ˜ν•œ μ „λ₯˜ 증배 μ •λ₯˜νšŒλ‘œλ₯Ό μ‚¬μš©ν–ˆμ„ 경우 λ°œμƒν•˜λŠ” μ „λ₯˜ λΆˆκ· ν˜• ν˜„μƒμ˜ 원인을 νŒŒμ•…ν•˜κΈ° μœ„ν•΄ μ •μƒμƒνƒœ 뢄석을 μˆ˜ν–‰ν•˜μ—¬ 이 ν˜„μƒμ΄ μ˜μ „μ•• μŠ€μœ„μΉ­μ— μ–΄λ–€ 영ν–₯을 μ£ΌλŠ”μ§€ ν™•μΈν•œλ‹€. λ³Έ λ…Όλ¬Έμ˜ 타당성을 κ²€μ¦ν•˜κΈ° μœ„ν•΄ λͺ¨μ˜ μ‹€ν—˜κ³Ό 240 WκΈ‰ ν”„λ‘œν† νƒ€μž… μ‹€ν—˜μ„ 톡해 κ°œμ„ λœ μ˜μ „μ•• μŠ€μœ„μΉ­μ„ ν™•μΈν•˜κ³  비ꡐꡰ 회둜둜 μ‚¬μš©λœ 일반적인 λŠ₯동 ν΄λž¨ν”„ ν¬μ›Œλ“œ 컨버터와 λΉ„λŒ€μΉ­ ν•˜ν”„λΈŒλ¦¬μ§€ μ»¨λ²„ν„°μ™€μ˜ 효율 비ꡐλ₯Ό 톡해 효율이 κ°œμ„ λ¨μ„ 보인닀.Maste

    A new bidirectional AC-DC converter using matrix converter and Z-source converter topologies

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    This thesis proposes a new bidirectional three-phase AC-DC power converter using matrix converter and Z-source inverter topologies. Advantages of the AC-DC matrix converter are the inherently controllable power factor, the tight DC voltage regulation, the wide bandwidth with quick response to load variation, the single-stage buck-voltage AC-to-DC power conversion; advantages of the z-source inverter are the increased reliability by allowing the shoot-through between upper and lower power switches of one inverter leg, insensitivity to DC bus voltage due to the extra freedom of controlling DC-link voltage. The proposed Matrix-Z-source converter (MZC) marries up both advantages of AC-DC matrix converter and Z-source inverter. It can achieve voltage-boost DC-AC inversion capable of variable voltage variable frequency (VVVF) AC output; it can achieve voltage-buck AC-DC rectification capable of inherent control over AC current phase angle and DC output regulation with a (VVVF) AC source supply. Both foresaid performance in DC-AC inversion and AC-DC rectification can be implemented in a simple open-loop control manner. Three constraints of VSI, in the bidirectional AC-DC power conversion, are the peak AC voltages are always less than DC-link voltage, closed-loop control has to be employed when DC regulation and/or AC current phase angle control are required, and AC voltage is sensitive to the variation of the DC-link voltage in DC-AC inversion. The voltage-boost inversion and/or voltage-buck rectification of MZC overcomes the first constraint; thus MZC enables the AC machine voltage increased higher than DC-link voltage hence advantages of running AC machine at relatively high voltages are enabled. The direct DC voltage regulation and inherent AC-current-phase-angle control of MZC overcomes the second constraint in an open-loop manner; hence a simplified system design is obtained with sufficient room for the further improvement by closed-loop control schemes. The extra freedom in controlling DC-link voltage of MZC overcomes the third constraint hence a DC source voltage adaptable inverter is obtained. This thesis focuses on the study of the feasibility of the proposed MZC through theoretical analysis and experimental verification. At first, the proposed MZC is conceptually constructed by examining the quadrant operation of AC-DC matrix converter and Z-source inverter. After the examination of the operating principles of both AC-DC matrix converter and Z-source inverter, the configuration of MZC is then proposed. The MZC has two operating modes: DC-AC inversion and AC-DC rectification. Circuit analysis for both operating modes shows that the new topology does not impose critical conflict in circuit design or extra restriction in parameterization. On the contrary, one version of the proposed MZC can make full advantage of Z-source network components in both operating modes, i.e. a pair of Z-source inductor and capacitor can be used as low-pass filter in AC-DC rectification. The modulation strategy, average modeling of system, and features of critical variables for circuit design of the proposed MZC were examined for each operating mode. Simulations of the proposed MZC and its experimental verification have been presented. Analytical models of conduction and switching losses of the power-switch network in different operating mode have shown that the losses in the MZC compare favorably with conventional VSI for a range of power factor and modulation indices
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