基于Crowbar与Buck电路对双馈风力发电机LVRT的研究

Research on Double-fed Wind Turbine Generator LVRT Based on Crowbar and Buck Circuits

在双馈风力发电系统中,当电网电压跌落较严重时,传统的改变励磁的控制策略或仅在转子侧引入撬棒(Crowbar)保护电路,已不能满足电压跌落时低压穿越(LVRT)的要求,论文在直流侧引入了卸荷(Buck)保护电路协同转子侧主动式Crowbar保护电路工作,更有助于跌落电压的恢复,大大提高了并网电压低压穿越的能力。首先对双馈风力发电机(DFIG)建立数学模型并进行暂态特性分析,推导相关故障电压电流表达式,然后对Crowbar保护电路和Buck保护电路阻值进行整定。通过仿真分析验证了组合保护电路的可行性与优越性。

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.