Advanced Isolated Bi-Directional DC-DC Converter Technology for Smart Grid Applications
The growing concerns for environment, increasing demand growth and threat of energy shortage continue to accentuate the request of upgrading the traditional power grid. Smart grid is envisioned to take advantage of all available modern technologies in transforming the current grid to one that functi...
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| Format: | Others |
| Language: | English English |
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Florida State University
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| Online Access: | http://purl.flvc.org/fsu/fd/FSU_migr_etd-8709 |
| Summary: | The growing concerns for environment, increasing demand growth and threat of energy shortage continue to accentuate the request of upgrading the traditional power grid. Smart grid is envisioned to take advantage of all available modern technologies in transforming the current grid to one that functions more intelligently to facilitate integration of renewable energy source and energy storages, to provide higher quality of service and so on. Solid State Transformer (SST) is an essential technology for integration of the distributed energy resources, distributed energy storage, and intelligent loads. It has the advantages of its reduced size and weight/volume with high frequency transformer, high power density, and good power quality. Comparing to other SST topologies, the three-stage SST is more promising due to its advantages to provide power factor correction, reactive power compensation and an additional regulated DC bus The bi-directional dc-dc converter is the key stage in the three-stage SST topology configuration since it provides not only the high frequency galvanic isolation, but also determines the system overall efficiency and power density. Therefore, the dc-dc converter promising dynamic performance is the key requirement for the three-stage SST. Currently, few literatures research on the three-stage SST system dynamics, especially for the soft start-up issue. Three-stage SST requires a delicate start-up control scheme because of three conversion stages and high frequency transformer. The major challenge of researching start-up issue is how to develop a theoretical analysis strategy to study different schemes. The thesis researches this issue by formulating the transformer instaneous peak current with respects to all the key impact factors. As a result, different schemes can be investigated by using a unified formula. Moreover, a new soft start-up scheme is proposed with the minimized transformer current response. The thorough analysis of the DC-DC converter transformer current during the three-stage SST start-up and the proposed start-up scheme is described in details in chapter 2. Fuel cell is an important renewable energy source of distributed energy storage device for new mobile applications and power generation system since it offers high efficiency, low emissions of regulated pollutants and excellent part-load performance. The major challenge for fuel cell power conditioning system is to limit the fuel cell low-frequency current ripple resulted from the inverter load. The traditional solution is to adopt the large electrolytic capacitor as the energy buffer. However, the large-sized electrolytic capacitors will decrease the system lifetime as well as increase the system volume and cost. A new current-fed phase-shift controlled dc-dc converter based fuel cell power conditioning system is proposed in this thesis with low-frequency ripple free input current using a control-oriented power pulsation decoupling control scheme. Without adding any extra components, the proposed fuel cell converter realizes the power pulsation decoupling function so as to reduce the dc bus capacitor, thus allowing for choosing long lifetime film capacitor to replace the bulky electrolytic capacitor. The proposed decoupling control design is based on the system small-signal average model. The detailed system operation analysis and proposed decoupling control design guideline is presented in chapter 3. The chapter 4 summarizes the dissertation work. === A Dissertation submitted to the Department of Electrical and Computer Engineering in partial fulfillment of the
requirements for the degree of Doctor of Philosophy. === Fall Semester, 2013. === September 13, 2013. === Electrolytic-Capacitor Free, Fuel Cell, Smart Grid, Soft Start-Up, Solid-State Transformers === Includes bibliographical references. === Hui Li, Professor Directing Dissertation; Juan Ordonez, University Representative; Uwe H. Meyer-Baese, Committee Member; Jim P. Zheng, Committee Member; Chris S. Edrington, Committee Member. |
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