风电场电网电压跌落恢复过程中若无功过剩、负载突然切除以及风电场35 kV非有效接地系统因单相接地故障引发谐振过电压,电网电压面临升高风险.由于双馈型风力发电机定子与电网相连,电网电压骤升时其暂态过程会造成定转子电压电流冲击和电机转矩振荡.为实现机组高电压穿越,针对电网电压骤升期间变流器不脱网的保护,拓扑上增加了直流Chopper电路,制定了一套穿越期间的脉冲管理逻辑.从变流器模型最大输出电压出发,提出了网侧无功优先的控制策略.转子侧变流器引进转子附加阻尼控制,加快直流磁链衰减,避免直流Chopper频繁动作,减轻机组转矩振荡过程.通过Simulink建立主回路模型,在控制程序嵌入Simulink作为控制器的方式进行混合仿真,更加逼近现场环境.结果验证了所提策略与保护方案的有效性和可行性,同时也验证了程序代码的正确性.%Surplus of reactive power at recovery progress after grid voltage dips,suddenly removed load and resonance over-voltage because of single phase to earth fault in the neural indirectly grounded power systems will cause grid surge.For the stator of doubly-fed wind power generator connected to grid,the transient process of grid surging will cause the stator voltage and current shock and motor torque oscillate.DC chopper circuit is added and pulse-management-control logic is formulated to achieve the protection of converter to ride through grid voltage soared period.The grid reactive power priority strategy is proposed in order to output maximum voltage.Besides,virtual rotor damping control is used on converter to speed up DC magnetic relaxation,avoid DC Chopper frequently operation and alleviate oscillation of the motor torque.Model of main electricity circuit is established by Simulink and program is embedded in Simulink as a controller module in the hybrid simulation in order to be close to the actual circumstances.According to the simulation results,the validity and feasibility of strategy and protection scheme are proved.Besides,the accuracy of the program code is confirmed.
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