基于暂态磁链补偿前馈的DFIG低穿强励直流灭磁方法

Forceful Demagnetization of DC Component Based on Transient Feedforward Compensation During DFIG's LVRT

低电压穿越能力是双馈风电机组(DFIG)最重要的性能指标之一。网压跌落时,应用Crowbar电路使得转子变流器闭锁,转子电流处于暂态过程。针对采用Crowbar电路限制DFIG转子侧过电流和直流侧过电压存在的不足,论文提出一种基于转子电流源控制且电流指令一阶导数恒定的低压穿越强励直流灭磁控制策略,并给出灭磁电流归零的约束条件及转子暂态电流可控的必要条件,实现低压跌落过程及电压恢复过程电机直流磁链分量的强制衰减和灭磁过程后转子交流励磁电流的快速控制,显著降低了机组在低压穿越过程的无功消纳。仿真及实验结果验证了理论分析的正确性,为双馈风电系统的低压穿越提供了一种有效的控制方案。

The ability of low voltage ride through（LVRT） is one of the most important performance for doubly-fed induction generator（DFIG）.The application of Crowbar circuit makes the IGBTs of rotor side converter（RSC） be switched off during LVRT,while the transient current of DFIG is under the condition of natural attenuation.Aiming at the deficiency of over current or over voltage for RSC applying Crowbar circuit,one kind of strategy based on current source controlling of the rotor while the command is changing with a constant rate is proposed for demagnetization of the transient DC flux component.Then the demagnetization current＇s making zero and the necessary condition of transient rotor current＇s controlling is researched.The transient controller of rotor current implements the forceful DC demagnetization and the AC excitation of rotor with rapid response after the DC demagnetization.The reactive power consumption is reduced during LVRT compared with the strategy applying Crowbar.The dynamic simulation and experiment validated the correctness of the theory researched and shows feasibility of the strategy.