Research On Low Voltage Ride Through Control Strategy Of Doubly-Fed Wind Power Generation System

With the continuous development and utilization of new energy today,wind energy,as a clean renewable energy,has become a research object of close attention in today's world due to its high utilization rate and the maturity of current development technology.With the continuous research on wind energy,the wind energy market is developing rapidly,the market is constantly opening and expanding,and the installed capacity of wind power is constantly expanding.The influence of the stable operation of the wind farm to grid are also growing,so more and more strict with the interconnection of large wind farms,wind turbines have a certain low voltage across(LVRT)capability,make the grid voltage dips,wind turbines to the power grid of reactive power compensation to grid voltage can be quickly recover and parallel operation,how to improve the ability of low voltage across a race to the problems in the research of scholars both at home and abroad.At first,this paper studied the low voltage through the control strategy of scholars both at home and abroad,and studies the doubly-fed wind power generator,machine and side net current transformer is the important part of the structure and principle,and mathematical model is established,and detailed study of the machine side and network side of the traditional control strategy,and then to the doubly-fed wind power generation system in the event of a power grid voltage transient characteristics of the three-phase symmetrical fall was analyzed,and the research system during the failure of the rotor tilting the root cause of the current and dc bus voltage rise,the shortcomings of traditional control strategy combining,Is proposed based on MPAFA algorithm(multiple parameters of the parallel adaptive step length and attract degree of firefly algorithm)to optimize the fuzzy PI control,in order to verify the effectiveness of the proposed control strategy,through the MATLAB/SIMULINK simulation compared the simulation figure of three kinds of control strategies are traditional control strategy of control strategy is put forward,the firefly algorithm to optimize the fuzzy PI control strategy and the proposed fuzzy PI control strategy based on MPAFA,results show that the proposed control strategy in the effectiveness of the power grid voltage when 20% down.Followed by further research in this paper,the depth of the power grid voltage drop of the control strategy,joined the Crowbar circuit in the rotor side and dc side,first studied the Crowbar circuit structure and topology graph,secondly puts forward the Crowbar circuit for strategy selection of resistance and energy dissipation principle,through the simulation analysis of selection of energy dissipation resistance is obtained under the principle of selecting threshold and verify the effectiveness of the selection principle.At last,through the simulation,compared with 70% drop in the power grid voltage amplitude Crowbar circuit and MPAFA algorithm to optimize the effectiveness of the fuzzy PI control strategy combining,The simulation results show that the input of Crowbar circuit and the combination of the fuzzy PI control strategy optimized by MPAFA algorithm can effectively suppress the rotor side overcurrent,stabilize the dc bus voltage,and significantly improve the low-voltage crossing capability of double-fed wind power generation system.