Study On Modeling And Control Strategy For Distributed Generation Based Micro-grid System

With the exhaustion of fossil energy, and the continuous development of new energy, broad prospects for development of distributed generation are shown. Distributed generation is a new way to generate electricity characterized with environmental protection, high flexibility, modularization and high efficiency. But many of distributed powers accessing to power grid increases the variety of adverse factors. The micro-grid technology can solve this problem. Micro-grid technology attracts more attention, and therefore it is of great significance for the study on distributed generation and micro-grid technology.Many simulation models of photovoltaic cells are built, but they lack of systematic classification in current research. The design of photovoltaic (PV)-battery hybrid power system generally ignores the over-current protection. Furthermore, simulation platform for systematic control strategy is still uncommon in micro-grid research. To overcome the above shortcomings, this thesis mainly studies two micro sources like photovoltaic cells and solid-oxide-fuel-cell (SOFC) power, and focuses on the study of relevant technologies from three levels such as modeling and simulation of micro source in distributed generation, grid-connected control for single distributed micro source, and operational control of micro grid composed of multiple micro sources. Meanwhile, the foundation platform for simulation is established. The main contents are summarized as follows:1. Three kinds of photovoltaic cell simulation models, which can effectively realize the analog for real working conditions, are systematically analyzed and established. Perturbation and observation control method and conductance increment method are comparatively analyzed, and the former method is selected to realize MPPT tracking. Medium-term dynamic simulation model for SOFC is established, and then hysteretic current control method is used to achieve effective output of SOFC.2. A kind of structure for PV-battery hybrid generation system is designed in order to study the control strategy for bi-directional DC/DC converter. In addition, the effectiveness of the designed system is verified through simulation.3. The principles of three types of control strategies (PQ、V/f and Droop control strategy) for micro-grid are studied. Three simulation examples are established to verify the effectiveness of each kind of control strategy. Corresponding simulation examples aimed at master-slave control and peer-to-peer control for micro-grid are designed to verify these two control modes.4. On the basis of photovoltaic cell and SOFC models, the control strategies for PV-battery hybrid generation system, SOFC system and micro-grid are studied, thereby a foundation platform for simulation is built as the basis for further studies.