限电弃风工况下双馈风电机组有功及调频控制策略

The Control Strategy of Active Power and Frequency Regulation of DFIG Under Wind Abandon Condition

双馈风电机组限电弃风运行能够为电网提供备用和频率支撑。为减小限电弃风工况下转速和桨距角频繁动作致使机组产生的机械疲劳,提出一种基于机组运行点转移轨迹优化的有功控制策略,并通过引入下垂控制使其具备了参与电网一次调频的功能。对限电弃风工况下机组在不同运行点处的稳定性进行分析;考虑机组有功平衡及运行点稳定性等约束条件,建立以转速和桨距角综合调整量最小为目标函数的运行点转移轨迹优化模型,并提出优化模型在出现不可行解时的处理机制,以获得可行的最优转移轨迹;建立机组运行轨迹和调频控制器,并对变桨系统和转子侧变频器的传统控制策略进行改进,使机组能够沿最优转移轨迹调整有功和参与调频。仿真结果表明,利用所提控制策略能使机组在准确完成限电弃风任务并为电网提供频率支撑的同时,大大减少机组转速和桨距角的调整量。

Doubly fed induction generator （DFIG） wind turbines can provide power reserve and frequency support for the grid under wind abandon condition. In order to reduce the mechanical fatigue caused by frequent adjustment of rotor speed and pith angle, an active power and primary frequency control strategy based on the power balance, operation point stability et al. are considered as the constraints. A method dealing with infeasible solution is proposed to obtain the optimal feasible transfer trajectory. Finally, to realize the active power control and the grid frequency regulation, an operation trajectory and a frequency regulation controller are established and the traditional control strategies for pitch system and rotor side converter are improved, which ensures that the wind turbines can track the optimal transfer trajectory. The simulation results show that the control strategy can reduce the adjustment of rotor speed and pith angle dramatically while completing the task of wind abandon and providing frequency support for grid.