Research on Double-fed Wind Turbine Generator LVRT Based on Crowbar and Buck Circuits
In the doubly-fed wind generation system,when the grid voltage drop is serious,the traditional excitation control strategy or only introducing crowbar protection circuit on the rotor side can no longer meet the requirements of low voltage crossing when voltage drop(LVRT),this paper introduces buck protection circuit on the DC side to cooperate with the rotor side active crow-bar protection circuit,which more helps to the drop voltage recovery and greatly improves the ability of network voltage crossing.First the mathematical model of doubly-fed wind generator(DFIG)is built,the transient characteristic is analyzed,the relevant fault voltage current expression is derived,and then the resistance value of crowbar protection circuit and buck protection circuit are fixed.The feasibility and superiority of the combined protection circuit are verified through simulation analysis.
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