Research On Network Operation Hybrid Control For Photovoltaic Microgrid Flexible Inverter

It has gradually become the world consensus to vigorously develop photovoltaic technology for it’s abundant resources, widespread distribution, simple construction, environmentally friendly, etc. Accessing to the main power grid in the form of micro-grid, which is the most effective measures to improve its effectiveness for distributed PV. For its’ randomness and intermittent characteristics, all kinds of problems occur when the photovoltaic microgrid connected to the main grid. Therefore, it becomes a hot topic to study the photovoltaic microgrid grid-connected power interface and its control method. This thesis studied the grid-connected flexible inverter, and launched a research on hybrid control theory and methods of the network operation of the PV microgrid flexible inverter, which has not only extremely important academic significance, but also a very wide range of applications.Firstly, the background and development, the concept, and domestic and international development of micro-grid are introduced; the conventional microgrid grid-connected interface and its traditional control methods are summarized; the basic concept, classification, principle and research status of flexible converter are focused on; Moreover, the basic topology and working principle of the grid-connected flexible converter are deeply studied.Secondly, the Concepts, models, classification and the control method of hybrid system theory are studied. Detailed analysis of the hybrid feature of the grid-connected operation system of the PV microgrid flexible inverter was made. Combining the inverter working mode and hybrid control decision-making mechanism of three-phase full-bridge inverter of the flexible grid-connected inverter, the establishment of three-phase full-bridge inverter hybrid automata model was made, and the design method of discrete controller and continuous controller of flexible grid-connected inverter is proposed.Finally, a simulation model for micro-grid photovoltaic network operation system is developed on the Matlab/Simulink software, and the system under different operation modes and working conditions is simulated and analyzed.The proposed grid-connected flexible inverter for photovoltaic micro-grid, as one of high-power electronic power interface, can self-regulate its topology and output function according to photovoltaic power output capacity or other external information. The network operation hybrid control method for micro-grid photovoltaic flexible inverter is deep studied in this article, it is able to objectively, accurately describe continuous features, discrete features and their interactions of micro-grid photovoltaic network operation systems. The designed hybrid controller for the flexible grid-connected inverter, can achieve flexible and versatile power control, power quality control, operation mode switching control. The controller has high control accuracy, robustness, ease of implementation and other advantages. Simulation results verify its correctness, validity and feasibility.