电网故障不脱网运行的研究

摘要

为保证电网运行安全,需要采用自身的控制策略来抑制轻微电网电压跌落,主要是在故障下对网侧和机侧变换器的控制策略进行调整,即在严重电网跌落时,采用Crowbar装置在电压跌落时为转子浪涌电流提供通路,并限制转子电流的增大,在电压恢复时抑制电压骤升.此处提出一种Crowbar控制策略,能有效抑制转子过电流、直流母线过电压,并可向电网注入无功电流以帮助恢复电网电压.测量结果表明此控制方式能使双馈感应发电机( DFIG)在电压跌落故障下实现不间断运行,有效提高了DFIG风电机组运行的可靠性.%To ensure the safe operation of grid,it's necessary to limit the slight severe grid voltage dips,the main is to adjust grid-side and motor-side converter's control strategy in low voltage emergency conditions.In severe grid volt age dips,it's necessary to limit the high inrush rotor current and provide a bypass for it via a Crowbar connected to the rotor windings.A novel Crowbar control strategy is proposed to limit the over current in the rotor and the over voltage of the DC bus.Moreover,a capacitive current is injected into the grid to assist the recovery of the grid voltage. The simulation results prove that with this control strategy the doubly fed induction generator (DFIG) is able to ride through the more severe grid voltage dips,thereby the operation reliability of DFIG sets can be improved effectively.