基于转矩极限的双馈风机改进频率控制方案

转矩极限控制利用双馈风机（DFIG）的转子动能提供惯性响应，存在减速初期功率下降过快以及在加速阶段转速恢复速度较慢的问题。针对该问题，提出了一种改进频率控制方案。在减速阶段双馈风机提供恒定有功支撑，直至转子的动能达到最低限值或频率到达最低点，然后有功输出随转速线性下降，直到与机械功率的差额趋近于0；在加速阶段，双馈风机有功先随时间下降，然后维持恒定至与最大功率跟踪输出值相等。该方案能有效减小系统频率跌落幅度，同时避免二次跌落，且在较短时间内恢复转速。基于Matlab/Simulink仿真平台建立含风电场的3机9节点模型，通过仿真验证了所提控制方案的有效性和优越性。

Improved Frequency Control Scheme for Doubly-fed Wind Turbine Based on Torque Limit

The torque limit control provides inertial response by utilizing the kinetic energy of doubly-fed induction generator （DFIG）. This scheme has the problem that the power drops rapidly at the initial stage of deceleration， and the rotor speed recovery is slow during the acceleration stage. Aiming at these problems， this paper proposes an improved frequency control scheme. In the deceleration stage， the DFIG provides constant active power support until the rotor kinetic energy reaches the lowest limit or the frequency approaches the nadir. And then the active power output decreases linearly with the speed until the difference with the mechanical power approaches zero. In the acceleration stage， the DFIG first reduces the active power with time and then maintains the active power until satisfying the maximum power point tracking power. This scheme can improve the frequency nadir， avoid the second drop and restore the speed in a short time. Three-machine and nine-node model with wind farm is set up in the Matlab/Simulink environment. The simulation results verify the effectiveness and superiority of the scheme.