Abstract
This thesis presents the development of a bidirectional inverter and operation control between DC micro-grid and utility grid. Through proper control for the developed inverter system, it possesses flexible and high-performance bidirectional power flow control capability. The DC micro-grid is connected to the utility grid via the inverter by the developed phase-locked-loop (PLL) synchronization process. The grid connected power conditioning control operation can be divided into three modes: (i) Discharging mode: all the local load real and reactive powers are supplied from the micro-grid. Moreover, the programmed powers can also be sent back to the utility grid; (ii) Charging mode: the utility grid supplies power to the DC micro-grid and local loads. In particular, the battery bank in micro-grid is charged from the mains; (iii) Floating mode: all the local loads are powered from the utility grid. When the utility grid failure occurs, the synchronization switch is opened to isolate the micro-grid. The inverter system is operated in inverter mode. The inverter system supply uninterruptible power from DC micro-grid to the load. The proposed inverter system possesses the combined functions of power conditioner, active power filter and uninterruptible power supply (UPS). In addition, the DC micro-grid can also be supported energy from a plug-in AC/DC converter system. It consists of a three-phase single-switch (3P1SW) switch-mode rectifier(SMR) and a LLC resonant DC/DC isolated converter. The AC input source may be provided from backup distribution network, wind generator, micro-turbine, fly-wheel generator, and hybrid-electric vehicle generator, etc. The controls of all constituted power stages are realized digitally using digital signal processor (DSP). Some simulated and experimental results are provided to verify the operating performance of the established system.