An active power control strategy for doubly-fed wind turbines which join in active power control of wind farms
Actual operating data shows that the `free' operation of wind farms has a significant anti-regulation characteristics. With the increasing access capacity of wind power, it not only increases the difficulty of scheduling and peaking, but also affects the access capacity of wind farms to the power system. Therefore, the relevant standards and requirements are developed by the state and state grid corporation, which ask wind farms to participate in active power control of the power system by receiving instructions of the scheduling. It is required that wind farms should participate in active power control of the power system. To achieve this goal, it is needed that wind turbines control the active power in accordance with instructions issued by the control system of wind farms. But most of wind turbines use MPPT operation mode at present, it is difficult to meet the requirements of wind farms' active power control. To solve this problem, power drop operation principle of doubly-fed induction wind turbine is analyzed, Then the active power control modes of wind turbines which is fit for different wind power and the control strategy of switch among control modes are proposed. Finally, the validity of proposed control strategy is verified by simulating based on DIgSILENT/PowerFactory.