| With the development of distributed generation,the distribution network with high penetration continues to increase,and its impact on the power grid is becoming more and more important.With the increase of the capacity of the distributed power supply,the current grid-connected standards at home and abroad all require the distributed power supply to have certain low-voltage traversing capability,low-voltage traversal capability has become one of the basic requirements of grid-connection criteria for large-scale distributed generation.Low voltage traversing technology as the protection of power grid restoration has become the key problem to be solved.In this paper,the low voltage traversing problem of distribution network with high permeability distributed power supply is studied as follows:Firstly,this paper discusses the mathematical models of different types of distributed power sources based on the principles of different types of distributed power sources,and in Matlab / Simulink simulation software,a dynamic simulation model of distributed power supply,such as photovoltaic system,wind power system and storage battery,is established,and the correctness of the model is verified,it can be used as a reference for the low voltage traversing engineering of distribution network with high permeability distributed power supply.Secondly,on the basis of analyzing the principle of PQ control,Droop Control,V / F control,etc.,the control strategies including master-slave control,peer-to-peer control and hierarchical control based on multi-Agent technology are analyzed.A typical simulation model of micro-grid system is built in Matlab / Simulink software,and the micro-grid system under the grid-connected operation mode and the off-grid operation mode is simulated and analyzed,the accuracy and applicability of the simulation model are verified.Finally,in the simulation model of micro-grid system,the low-voltage control strategy is verified.In this paper,the master-slave control mode is selected for Microgrid.In the grid-connected state,the voltage and frequency of the micro-grid are supported by the large-scale TV network.In the event of grid failure or other conditions leading to off-grid,themicro-grid loses the voltage and frequency support of the large-scale Grid.The optical storage solar inverter of the micro-grid will switch to VF control to provide stable voltage and frequency for the load,the double-fed Fan avoids the impact of heavy current through the Crowbar circuit until the power grid is restored.The simulation results show that the LVRT(Low voltage ride through,LVRT)control strategy can be used to make the Crowbar Circuit Act as a protection circuit,which can provide a bypass for the rotor-side converter,while the part of the grid-side converter is not changed,it can also output some reactive power for the recovery of the grid voltage and realize low-voltage traversing. |
