Study Of Digital Simulation Platform Of Micro-grid Based On RTDS

Microgrid is one of the important forms of the connection operation of distributedgenerations. Since the Microgrid includes a large number of power electronic devicesand complex control strategies, comprehensive understanding and grasp itscharacteristics are the basis to ensure the normal operation of the Microgrid. Thesimulation is one of the most important means of in-depth understanding and analysisof the characteristics of the microgrid. The traditional method of simulation isphysical simulation which is interconnected with actual devices. The advantage of thissimulation method is intuitive, vivid；But its shortcomings are also prominent：First,its investment is large, so that it has poor economy; Secondly, the device parameterscan not be flexibly adjusted, flexible and convenient are not enough to make thesimulation work; finally, its simulation function is seldom and its difficult toexpansion.Because of the limitations of the physical simulation, this article has built adigital Microgrid simulation platform on Real Time Digital Simulator.It has realizedthe comprehensive and in-depth simulation in operating and controling of distributedpower and Microgrid. Research contents and results are as follows:(1) This paper builts the models of major equipments of the Microgrid on RealTime Digital Simulator such as:I.Typical models for distributed generation, including the model of constantspeed constant frequency wind power system, doubly-fed VSCF, direct-drivepermanent magnet VSCF, PV and micro-gas turbine model, flywheel energy storagemodel, battery energy storage model, super capacitor energy storage model. Thesemodels provide a solid foundation for simulation of micro-networks.II. Coordinated control strategy models, including the PQ control of thegrid-connected Microgrid, master-slave and peer to peer control of the isolatedMicrogrid. These models ensure the simulation of the Microgrid which has differentoperation modes.III. Protection models, including the protection of Microgrid lines, protection ofMicrogrid load, protection of DG.(2)Aiming at promptness and stability tracking of maximum wind power whilevariable speed constant frequency wind power generation system running under ratedwind speed, with considering constraint of mechanical torque variation, a novelcontrol strategy based on sliding mode based extremum seeking control (SM-ESC) system for optimally tracking of maximum wind power is proposed and its stability isproved through proposition. To achieve higher control quality, an adaptive adjustmentmethod is further presented on the basic of stabilizing conditions of SM-ESC system,avoiding complicated manually parameter adjustment. The constraint of mechanicaltorque variation can be taken into account through deduction and analyzing processby just adding a rotor speed reference reflimited link in SM-ESC system and withthe adaptive adjustment method to determine the corresponding limit; thus makessmooth variation of mechanical torque without swings when tracking the optimumoutput curve, partly reducing the mechanical fatigue extent and prolonging service lifeof generation system.The above micro-network simulation system is about to be used for thesimulation work of the actual Microgrid system，and has been extended to two powercompanies, proved the significance of this study.