Research On Master-slave Control Strategy Of Island Microgrid

Microgrid technology can not only effectivly intergrate many kinds of Distributed generations(DG),but also play as a componet unit of energy internet in the future.Consequently the research on microgrid technology is very important.Research dierections of microgrid concentrate on three aspects which included economics, power technology,management and market.Cooperative control strategy especially in microgrid control techonology is key to ensure the safety of microgrid operation.This paper studies on operation control of microgrid in depth.Firstly,according to objectives of grid-connected contorl, the grid-connected control strategy is proposed through analysis of mathematical models for renewable DGs (photovoltaic power system,direct drive permanent magnet wind generation system).It not only can improve the utilization ratio of renewable DGs.but also maintain the unity power factor operation.Secondly,simulation model of battery energy storage system in island microgrid is built based on master-slave control strategy.Then the smooth switchover control strategies from grid-connected mode to islanded mode and from islanded mode to grid-connected mode are proposed,which in order to implement smooth transition between two operation modes.Thirdly, a new cooperative control strategy during islanded operation based on two-stage hierarchical control structure is proposed.It includes the selection of master unit(s),primary control,regional separation control,secondary control of microgrid central controller(MGCC),which implement no-error frequency and voltage stability control.Besides,this control strategy can not only reduce oscillation which caused by output power of slave unit(s) and load margin exceeds the capacity of master unit,but also provide enough spinning reserve margin for master unit(s) compared with the control strategy without secondary control.At last, a simulation platform of island microgrid is built under the environment of PSCAD/EMTDC.Grid-connected control strategy,smooth switchover control strategy and cooperative control strategy in islanded operation are respectively simulated under the simulation platform of microgrid. The simulation demonstrates effectiveness of the proposed control strategies.The research of this paper relies on a domestic islande microgrid demonstration project.A feasible operation control of microgrid and its mplementation method are proposed in this paper, which have certain references for the construction and application of the actual microgrid project.