| In order to cope with grid-connection of large-scale distributed generations(DG)with high penetration,improve the comprehensive utilization rate of energy and ensure the safety and stability of system operation,microgrid emerged.By virtue of its good energy management characteristics,the microgrid integrates a large number of dispersed DG into the power grid as a whole,reducing the impact risk of DG on the power grid.However,when dealing with the problems caused by modular DG grid-connection,the microgrid is often limited by its capacity,and due to the low degree of automation of the distribution network side,the scheduling technology is not advanced,which limits the consumption of high permeability DG by the distribution network and the optimization and adjustmen t of network topology.To deal with this problem,the researchers put forward the concept of Active Distribution Network(ADN)technology.In order to ensure the reliability of ADN operation and improve the quality of power supply,this paper proposes an A DN stategy of voltage coordinated control and method of optimization of power flow with microgrid.First of all,this paper elaborates the development status of microgrid technology and technology of active distribution network at home and abroad in detail,the method of optimization and control of microgrid is analyzed,and the principle of voltage control and optimization of power flow of active distribution network is studied,which serves as the system operation basis for implementing the strategy in this paper.Secondly,the control strategy and operation mode of microgrid are analyzed,and the control method of converter of microgrid adopted in this paper is deduced.In order to reduce the impulse current generated in the transient process of switching operation mode of the microgrid,a strategy of VF/Droop control is proposed in this paper to ensure the stability of system voltage and frequency,providing a feasible basis and theoretical basis for the microgrid grid-connection to participate in the voltage regulation and optimization of power flow of the active distribution network.Again,in this paper,an Active distribution network reactive voltage partition and control strategy considering microgrid participation is proposed.Through the power flow calculation,the sensitivity matrix of node voltages is obtained,and condensed clustering algorithm is used to build the control space of microgrid in ADN,which can help determine the cluster of controllable nodes dominated by the node accessed by the microgrid,a new Automatic Voltage Control(AVC)system with micro-network to support voltage control flexibly and fast is proposed.The developed AVC system can coordinate the operation between microgrid and conventional reactive compensation equipment,which realize quick and flexible voltage control without the need of involving supplement devices or modifying the distribution network,finally,a simulation model based on IEEE-33 system is established through the DIgSILENT/PowerFactory simulation software,the simulation results validate feasibility and effectiveness of the proposed voltage control strategy.Finally,based on the multi-agent system(MAS)ADN scheduling framework,a mathematical model of power flow calculation in active distribution network is established.Through this model,the characteristics and the existing problem of power flow calculation in distribution network dominated by renewable energy sources are analyzed and presents a strategy of power flow optimization to coordinate the output of microgrid and other regulating means.According to the proposed strategy of power flow optimization,the balance of internal power of the system is maintained,and the capacity of ADN to absorb renewable energy such as photovoltaic energy is impro ved.At last,a simulation model based on IEEE-33 system is established,the influence of grid-connected microgrid on node voltage,feeder power and light abandoning quantity of the system is studied,which proves the effectiveness of the proposed strategy in this paper. |
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