Control And Improvement For Distributed Generations Power Electric Devices In Microgrids

In order to make full use of distributed energy resources and to improve the reliability of power supplying system, microgrids becomes a hot topic of research in distributed energy systems in recent years . Lots of researching work mainly focusing on microgrids as well as its effects on power systems has been done. Meanwhile, the development of microgrids, especially the development of distributed generation, exerts great influence on traditional power systems and provides notable advancement to electrical technology. Microgrids solve the problems of high access costs and single DG control., and makes the generators, load, energy storage devices and control devices, etc. to form a single control unit in the sight of the system. And the generators in the microgrid, including fuel cells, micro gas turbines, photovoltaic cells, batteries and super capacitors, are all small units with electronic interface. Microgrid not only solves the large-scale access of DGs, take full advantages of them, but also give users a variety of other benefits. In this article, the characteristic and research status of microgrids are analyzed. Then the control strategies for AC microgrids and DC microgrids are separately discussed and distributed coordinated control strategies based on multi-agent system (MAS) are proposed.Because of the various kinds of distributed generations including in AC microgrids, in which every distributed generations is connected to the grid separately via a converter, the control style of electrical power system will develop from centralized system to distributed one. Under this situation, we should apply a more effective energy management system (EMS) - multi-agent system to ensure the reliability and efficiency of electrical power systems. Therefore, a new distributed coordinating control strategy based on multi-agent system (MAS) is proposed. This system is divided into three layers- Grids-layer, MicroGrids-layer and component-layer, the communication among the different layers and the agents in the lower layer is realized by Internet via Ethernet. The Grids-layer is energy management system, which is mainly responsible for monitoring the various MicroGrids and optimizing the algorithm to determine the output of MicroGrids . The MicroGrids-layer is responsible for monitoring the various components and optimizing the algorithm to determine the output of DGs . The component layer is a coordinated control system, which on the one hand is controlled by the upper agents, on the other hand has the ability to operate independently, mainly takes charge of the coordinated control of DGs in the microgrids. Through the application of MAS, the coordination between microgrids and the large power system will be more efficient.The distributed generations( include the batteries) in DC microgrids are all connected into DC network and the power is transmitted to customer load or upper grid via Inverters. It can save more inverters than AC microgrids and can control the output of distributed generations more easily according to the control of the DC voltage. So this article studies for the power electric devices in DC microgrids later and realize the effective use of the distributed energy.At the end of this dissertation, main results of the research are summarized and the further studies are prospected.