Research On The Control Strategy And Design Of A Central Controller In Microgrid

The Microgrid is a low voltage network with different micro-generators(micro-sources) and loads operating to supply electric power for the local area. Itcan operate in grid-connected or islanded, which has the ability to enhance thereliability of electrical energy supply. Most of micro-sources in a Microgrid areinterfaced through power electronic converters. The interfaces of convertersincrease the flexibility of control but reduce the inertia of the Microgrid.For a microgrid contains several Distributed Generators(DG), the key of asecure and stable operation is how to control the DGs, Distributed Storage(DS),local loads and switches coordinately and effectively so as to meet the localcustomers’demands as much as possible when the microgrid structure changes.Furthermore, the coordinated control is also a necessary for an economicaloperation of microgrid. Microgrid control center issued the DGs,DS and loadscontrol command to coordinate the operation of the entire microgrid, and maintainthe stability of the microgrid internal frequency, voltage and other indicators. Thestatic switch locates at the point of common coupling(PCC) to connect themicrogrid with the utility grid. It has the ability to autonomously island themicrogrid from disturbances such as faults or power quality events. After islanding,the reconnection of the microgrid is achieved autonomously after the tripping eventis no longer present. So the static switch is a link between the microgrid and utility,and it has a crucial role.On the basis of Agent Principle and MAS theory，an Agent and MAS-basedmicrogrid hierarchical distributed control system will realize operational control ofthe microgrid. And then the issues of how to realize the Agent control and how toimprove the coordination control strategies are disscused. Also the specialfunctions and control strategies of static switch agent are discussed in details.Using the Matlab/simulink, the transient of connection is simulated and studied, themicrogrid can operate stably and autonomously.Two control methods used in local controllers of DG are analyzed, includingPQ control and V/f control. And then the power management unit andsynchronization unit of MGCC are studied after the expatiation of structure andfunctions of MGCC. For the function of the MGCC requirements, this papercompared the advantages and disadvantages of the common hardware platform. Finally MGCC selected the platform based on ARM embedded hardware andintroduce the main controller chip and its peripheral circuit. An intelligent staticswitch system based on embedded system is designed. The main circuit deviceselection, the sampling circuit design, drive circuit design and protection circuitdesign is introduced in paper.