A Study on the Efficiency Improvement Method for Single-phase Boost Converter by Reducing Switching Loss

Switched mode converters have been widely employed to reduce the harmonics of the input current and are increasingly focused on the prevention of accidents and failure in the power system apparatuses. It is desirable that the switching frequency of the switch mode converters be set at a high frequency for effective harmonics reduction. High frequency operation, however, causes large switching power losses and degradation of the efficiency of the power conversion. To improve the efficiency, circuit configurations that can equivalently increase the switching frequency or use soft commutation techniques have been discussed. This paper proposes a new technique for improving the efficiency of single phase high frequency switch mode boost converter. This converter includes an additional boost converter that follows the main high frequency switching device. The additional converter, which is controlled at lower frequencies, bypasses almost all the current in the main switch and the high frequency switching loss is greatly reduced. Both switching devices are controlled by a simple methodeach controller consists of a one-shot multivibrator, a comparator and an AND gate, and the maximum switching frequency can be limited without any clock generator. The converter works cooperatively in high efficiency and acts as though it were a conventional high frequency switch mode converter with one switching device. This paper describes the proposed converter configuration, design, and discusses the steady state performance concerning the switching loss reduction and efficiency improvement. and the proposed method is verified by computer simulation.1. 서 론 1 1.1 연구배경 및 동향 1 1.2 연구목적 2 1.3 논문의 구성 3 2. DC-DC 컨버터의 종류 4 2.1 벅 컨버터 4 2.2 부스트 컨버터 7 2.2 벅 부스트 컨버터 11 3. 기존의 스위칭손실 저감 방법 15 3.1 반도체 스위치의 스위칭 손실 15 3.2 ZVS 컨버터 18 3.3 ZCS 컨버터 20 4. 부스트 컨버터의 스위칭손실 저감에 의한 효율개선 22 4.1 회로구성 22 4.2 컨버터의 제어방법 23 4.3 제어기의 실행 26 5. 시뮬레이션 29 6. 결 론 46 참고문헌 4

High step up DC-DC converter topology for PV systems and electric vehicles

This thesis presents new high step-up DC-DC converters for photovoltaic and electric vehicle applications. An asymmetric flyback-forward DC-DC converter is proposed for the PV system controlled by the MPPT algorithm. The second converter is a modular switched-capacitor DC-DC converter, it has the capability to operate with transistor and capacitor open-circuit faults in every module. The results from simulations and tests of the asymmetric DC-DC converters have suggested that the proposed converter has a 5% to 10% voltage gain ratio increased to the symmetric structures among 100W – 300W power (such as [3]) range while maintaining efficiency of 89%-93% when input voltage is in the range of 25 – 30 V. they also indicated that the softswitching technique has been achieved, which significantly reduce the power loss by 1.7%, which exceeds the same topology of the proposed converter without the softswitching technique. Moreover, the converters can maintain rated outputs under main transistor open circuit fault situation or capacitor open circuit faults. The simulation and test results of the proposed modularized switched-capacitor DC-DC converters indicate that the proposed converter has the potential of extension, it can be embedded with infinite module in simulation results, however, during experiment. The sign open circuit fault to the transistors and capacitors would have low impact to the proposed converters, only the current ripple on the input source would increase around 25% for 4-module switched-capacitor DC-DC converters. The developed converters can be applied to many applications where DC-DC voltage conversion is alighted. In addition to PVs and EVs. Since they can ride through some electrical faults in the devices, the developed converter will have economic implications to improve the system efficiency and reliability

Advances in Fuel Cell Vehicle Design

Factors such as global warming, dwindling fossil fuel reserves, and energy security concerns combine to indicate that a replacement for the internal combustion engine (ICE) vehicle is needed. Fuel cell vehicles have the potential to address the problems surrounding the ICE vehicle without imposing any significant restrictions on vehicle performance, driving range, or refuelling time. Though there are currently some obstacles to overcome before attaining the widespread commercialization of fuel cell vehicles, such as improvements in fuel cell and battery durability, development of a hydrogen infrastructure, and reduction of high costs, the fundamental concept of the fuel cell vehicle is strong: it is efficient, emits zero harmful emissions, and the hydrogen fuel can be produced from various renewable sources. Therefore, research on fuel cell vehicle design is imperative in order to improve vehicle performance and durability, increase efficiency, and reduce costs. This thesis makes a number of key contributions to the advancement of fuel cell vehicle design within two main research areas: powertrain design and DC/DC converters. With regards to powertrain design, this research presents a novel fuel cell-battery-ultracapacitor topology which shows reduced mass and cost, and increased efficiency, over other promising topologies found in the literature. A detailed vehicle simulator created in MATLAB/Simulink is used to perform a comprehensive parametric study on different fuel cell vehicle types, resulting in general conclusions for optimal topologies, as well as component types and sizes, for fuel cell vehicles. Next, a general analytical method to optimize the novel battery-ultracapacitor energy storage system based on maximizing efficiency, and minimizing cost and mass, is developed. With regards to DC/DC converters, it is important to design efficient and light-weight converters for use in fuel cell and other electric vehicles to improve overall vehicle fuel economy. Thus, this research presents a novel soft-switching method, the capacitor-switched regenerative snubber, for the high-power DC/DC boost converters commonly used in fuel cell vehicles. This circuit is shown to increase the efficiency and reduce the overall mass of the DC/DC boost converter

Автономні перетворювачі та перетворювачі частоти:

Зміст видання відповідає освітній програмі підготовки бакалаврів зі спе- ціальності 141 Електроенергетика, електротехніка та електромеханіка та програмі дисципліни «Силові перетворювачі автоматизованих електроприводів». Розглянуто напівпровідникові ключі сучасних перетворювачів енергії, переривники постійного струму (широтно-імпульсні перетворювачі), автономні інвертори напруги та струму, дволанкові та безпосередні перетворювачі частоти, імпульсні джерела живлення (DC/DC-перетворювачі, джерела безперебійного живлення). Для кожного зі згаданих перетворювачів проаналізовано принцип дії, характер електромагнітних процесів, основні співвідношення та характеристики, способи керування, регулювальні властивості, вибір елементів силового кола, шляхи поліпшення енергетичних показників, сфери використання. Значну увагу приділено автономним інверторам напруги (особливо з ШІМ) та перетворювачам частоти на їх основі, а також специфіці використання перетворювачів у складі електропривода (роботі на проти-ЕРС та в режимі рекуперації)