Research On The Control Technology Of AC Micro-Grid System For Isolated Islands

With the rise of renewable energy initiating a new round of energy revolution in recent years, distributed generation technology provides a breakthrough for the grid connection of renewable energy. And microgrid technology arises to achieve the efficient utilization of renewable energy and cope with the challenge from distributed generation. Microgrid features small investment, cleanness, environmental friendship, and flexible generation form, so it is an ideal choice for such areas of which the power supply is not covered by traditional grid as islands. It is imperative to carry out relevant research on micro-grid to meet the increasing power demand in rural areas.On the basis of the study of the pertinent concepts, topology structure and control technology of microgrid system for isolated islands, this thesis designs a AC microgrid scheme for isolated islands based on distributed wind power, solar power and energy storage hybrid generation system, and builds a physical model to verify the validity of the scheme. Main research contents of this thesis include:First, this thesis studies the generation principle and output characteristics of distributed generation on the basis of existing distributed generation equipment in the laboratory; analyzes the typical architecture and control method of microsource for isolated islands; and completes the design of AC micro-grid scheme for isolated islands in combination with actual demands.Second, this thesis, with reference to the thoughts of hierarchical control and energy management coordinated control, puts forward a power balance control strategy of AC isolated microgrid system by integrating the micro-grid scheme above. This strategy, with prediction at energy management station and generation plan as its benchmarks, in combination with real-time data, takes measures in all kinds of conditions of grid operation, so as to ensure the secure and stable operation of the microgrid system.Third, this thesis designs the micro grid central controller for isolated islands based on STM32F207 chip. In terms of hardware, its designs are mainly in the core circuit, power circuit, communication circuit, signal acquisition circuit, power metering circuit, control circuit and unloading circuit. In terms of software, it mainly focuses on the implementation of power parameter acquisition program, the communication protocol between the central controller and the energy management station and the control program; besides that, this thesis debugs the central controller to ensure the central controller’s reliable operation.Last, this thesis builds a model of AC isolated microgrid system and conducts relevant tests. The model is built with reasonably-chosen microgrid system components according to the design scheme. The model tests include model operation test of AC isolated microgrid, joint debugging of central controller and power management station, and verification test of the control strategy for power balance of AC isolated microgrid system. These tests suggest that the joint debugging of central controller and power management station is properly functioning, the model of AC isolated micro-grid system is stably running, and the control strategy for power balance of AC isolated microgrid system is reliable. This thesis is of positive significance to the practical implementation of microgrid technology.