|Title:||Investigation of high frequency DC to AC conversion and control techniques for high frequency power distribution|
|Subject:||Electric current converters|
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Electrical Engineering|
|Pages:||xvii, 166 leaves : ill. ; 30 cm.|
|Abstract:||The continual increasing capacity and performance of power distribution system presents severe challenges in modern energy industry. The traditional power distribution contains DC and AC. The existing DC power distribution confronts low efficiency and poor transient response, while low frequency AC power distribution suffers from lower power density, and slow dynamic performance. Hence, the conventional power distribution is far from enough in many power applications, such as aerospace, telecommunication, and computer system. High frequency AC power distribution system is to deliver the power with multi-kHz to mega-Hz, which has attracted the attentions from both industry and academia. This thesis highlights the high frequency power distribution from power source perspective. From the distribution architecture viewpoint, the power source feeds high frequency voltage and current to the AC transmission track, and load side converts the bus voltage to a specific low DC voltage or low frequency operational voltage. To obtain a power source with high efficiency and large power capacity, numerous works have been done in this thesis, which mainly focuses on the circuitry topology, modulation strategy, advance control algorithm, and system integration. Although the design of the high frequency inverter topology and corresponding control scheme is a challenging task, the achievements of this thesis partly solve large power capacity, parallel connection, and better control performance, which are significant for high frequency power source.|
Firstly, a novel switched-capacitor based cascaded multilevel inverter was presented to provide high frequency voltage output with lower output harmonics. Compared with conventional cascaded H-bridge inverter, the proposed inverter can greatly decrease the number of switching devices. Secondly, a unified phase-shifted modulation was presented to integrate the regulations of magnitude and phase. A controlled phase integrated with magnitude control can cut down the circulation current that is inevitable in parallel resonant inverters caused by component tolerance and parameter discrepancy. Thirdly, a μ-based controller was presented for single stage LCLC resonant inverter. Performance weights, as well as the perturbations from component tolerance and load variations are regarded as structure uncertainty. Lastly, a modified input-parallel output-series topology was presented to resolve synchronization issue. The transmission loss can be cut down via the lower transmission current and the higher transmission voltage. A power sharing controller with correlation control compensation was addressed to provide high quality output, flexible power capacity, and wide operation range. In this thesis, both simulation and experimental results are obtained from the prototype circuit to evaluate the effectiveness. This thesis contributes to the improvements of high frequency power source from different perspective. The aim is to propel high frequency system into the applications with high distance distribution and large power capacity, such as EV and Microgrid.
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