Analysis and design of power electronics systems for energy conversion
Description
The management of a variety of distributed resources for optimum energy efficiency could become an enabling technology to supplement the current energy system. Wind generators, micro-generators, photovoltaic generators, and fuel cells can be appropriately integrated to provide on-site power to consumers. For an increased system reliability and availability of a distributed supply system during outages of weather dependent sources, several energy storage devices may be employed in the energy conversion system. Consequently, a flexible control system needs to be developed to harness an optimal amount of power from a variety of sources when operating under both steady-state and transient conditions. In this dissertation, a novel high frequency multistage power conversion system is investigated for providing efficient energy transfer from a variety of sources to static, dynamic, linear, and nonlinear loads. The proposed multistage conversion system employs several power converters, including a six-pulse AC-DC rectifier, which contributes to the nonlinearity of the system, resulting in an increased harmonic distortion in the source current. Therefore, an attractive alternative to the six-pulse AC-DC rectifier is desired for the proposed energy conversion system Multipulse converters offer a substantially reduced value of distortion in the source current, making them potential alternatives for the standard front-end AC-DC rectifier. Multipulse converters, which consist of several series or parallel-connected rectifiers, produce a multistep source current as opposed to the three-step current offered by a six-pulse rectifier. Further reduction in the distortion can be achieved by adding more rectifiers, resulting in a higher pulse operation. However, an increase in the pulse number compromises the converter simplicity and cost due to complex transformer winding arrangements For improved performance and reduced component count, several hybrid multipulse converter topologies have been proposed. One investigated configuration employs an active current shaper, termed as the load compensator (LSTATCOM), for both the standard 12-pulse diode and thyristor converters. It is demonstrated that the LSTATCOM-based converter provides sinusoidal shaped source currents over wide variations in the output load and also compensates a limited amount of sag and swell in the source voltage