Abstract
This thesis develops a wind switched-reluctance generator (SRG) based DC micro-grid with battery energy storage buffer and three-phase load inverter. In the developed SRG, its power circuit is properly designed, and the hysteresis current-controlled PWM switching is applied to enhance the winding current control robustness against the adverse effects of back electromotive force. Then good generating performance under varying wind speed and load is achieved via proper voltage command setting, robust control and commutation shift. The SRG generated speed-dependent voltage is boosted and controlled by a current-fed push-pull interface converter to establish voltage well-regulated common DC bus. An active clamp circuit is equipped for increasing the operation reliability and efficiency of this DC/DC converter. The proposed micro-grid is supported by an energy storage system consisting of a flywheel and a lead-acid battery bank. The switched- reluctance motor (SRM) driven flywheel system is interfaced to the common DC bus through a bidirectional DC/DC converter. Good charging and discharging operation characteristics are obtained by properly designing the schematics and control schemes for the SRM drive and its followed interfaced converter. Similar to those of SRG, the voltage command of the SRM-driven flywheel in generating mode is also automatically adapted to the decreasing rotor speed and the voltage tracking error during the stored energy discharging. As to the battery energy storage system a bilateral buck/boost DC/DC converter is employed as an interface converter. Through proper circuit and controller designs, good common-bus DC voltage regulation in discharging mode and better charging performance are preserved. For making the performance experimental assessment, a three-phase load inverter is designed and implemented. The per-phase based control scheme is adopted, and the simple robust control is applied to yield good output voltage waveforms under linear and nonlinear loads. The control algorithms of all constituted power stages are realized fully digitally using digital signal processor (DSP). Normal operations and control performance of the established micro-grid are demonstrated experimentally.