Soft-switched high-frequency power converters for alternative energy systems

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World-wide increased energy demand with environmental concerns, alternative energy sources either integrated to the existing power grid or in a micro-grid utilizing hybrid ac and dc buses are becoming popular to ensure increased electrical energy security. The outputs of these energy sources vary widely including some operational limits, e.g.: permanent magnet synchronous generators (PMSG) used with wind turbines generate ac output of varying voltage and frequency; linear synchronous generators used in sea wave energy conversion have fluctuating power with varying amplitude and frequency output voltage waveform; fuel cells generate wide varying low voltage dc (22 to 41 V) having slow transient response for load changes while they are very sensitive to ripple currents.***   *When different energy sources are connected to a dc bus a bidirectional dc/dc converter is needed for battery or ultracapacitors charging as well as to supply the dc bus. A dc to ac inverter is required for utility interface to augment power generation or for standalone operation. Therefore, to satisfy the constraints imposed by these energy sources, low cost, highly efficient power electronic converters are indispensable part of such systems. This is possible using soft-switching converters operating with low losses and high switching frequencies having a number of advantages, e.g., high efficiency, small size, light weight, reduced EMI, low component stresses, etc. ***   *Therefore, main objectives of this work are: (1) to propose, analyze and design new high-frequency (HF) transformer isolated soft-switching single-phase and 3-phase power converter topologies (unidirectional and bidirectional dc/dc, dc/ac for utility interface and ac/dc with high power factor for PMSG and linear generators); (2) to develop soft-switched electronic transformers for direct ac/ac conversion; (3) interleaved operation for high power applications; and (4) to study the performance of designed converters using INTUSOFT SPICE or PSIM simulation software and building prototype experimental converters.***   *Proposed converters will have reduced size and weight (due to high switching frequency, low losses and HF transformer isolation) reducing their cost while satisfying the stringent requirements of energy sources. Ac/dc and ac/ac converters developed for wind and sea-wave generators will have high power factor, low harmonic distortion, some of them will have single stage power conversion with HF transformer isolation. With huge potential for power generation from sea wave and wind energy in Canada, proposed converters will be useful in such systems. This proposal is expected to train 3 Ph.D., 3 Master and several undergraduate students in the area of power electronics with emphasis on application to alternative energy systems. They will be trained in analysis, design, simulation and building of experimental converters.**