Research On Coordination And Autonomy Of Distributed Power Supply In Grid-connected Microgrid

With the increasingly prominent global energy and environmental problems and the rapid development of renewable energy generation technology,the proportion of new renewable energy in total energy is increasing.The structure of power system has changed from traditional centralized generation to centralized generation and distributed generation.Centralized generation is convenient for centralized dispatch and unified management,but it has a great impact on the power grid under abnormal conditions.Distributed generation is mostly directly connected to the distribution network side,which is close to the load.Through effective energy management,distributed generation can achieve immediate use,local absorption,reduce power transmission losses and improve energy efficiency,but it also brings great challenges to the stable operation of the power system.Under the background of increasing distributed energy penetration,this paper considers the construction of grid-connected micro-grid at the level of distribution network,which can be switched from smart switch to independent micro-grid operation,or to grid-connected operation,and the operation mode is more flexible.Through the flexible sag control of energy storage inverters in grid-connected microgrid,the coordinated control between sources and decentralized autonomous operation can be realized under isolated island conditions respectively.At the same time,the three-phase voltage source inverters with a certain voltage and frequency support function under grid-connected conditions are developed.The effectiveness of the proposed control strategy is verified by simulation and experiment.Considering that there are a certain number of diesel generator power supply in the actual grid-connected microgrid,and for the autonomous operation of diesel generator in the grid-connected microgrid,the corresponding flexible droop control strategy is proposed.The feasibility of the scheme is preliminarily verified by the design of controller and experimental platform.Finally,in view of the above research results,the coordinated control between the diesel generator and the inverter under decentralized conditions and the requirements of layered frequency and voltage regulation are realized by using the different characteristics of the diesel generator and the inverter.Furthermore,relying on the experimental platform of multi-energy complementary microgrid of Zhejiang University College of Engineering,a grid-connected microgrid platform with wind,light,diesel,storage and other energy sources is constructed,and the system internal-network-load coordinated control is realized by upper control.At the same time,the paper explores the possibility of applying grid-connected micro-grid to disaster conditions and realizes it.