## 1 Introduction
The tip speed ratio is controlled by the power converter. When the active power reaches the rated value, the pitch controller is activated to limit the active power to within the rated value. In [23; 24], the hybrid pitch controller was designed to improve the power quality and transient stability of the wind turbine. In the case that the wind turbine operates at the rated power, the pitch angle is controlled by the conventional Proportional Integral (PI) controller. In the case that the active power generation is lower than the rated power, the pitch angle is controlled by a Fuzzy Logic Controller (FLC). In this paper, it is assumed that the pitch angle is controlled based on the conventional PI controller for the wind speeds from the cut-in wind speed to the cut-out wind speed. For older wind turbines with low power capacity, the yaw control is normally used for the active power regulation (e.g., to suppress the excessive output power at high wind speed) [25]. Due to its limited dynamic response, the power capture is insensitive to the yaw angle, and the yaw system imposes an additional mechanical stress on the turbine, so the yaw control is not used for active power control in modern wind turbines with large capacity [26]. In this paper, the DFIG wind turbine with high power capacity keeps the yaw angle at 0\({}^{\circ}\) which means that the turbine blade faces the wind perpendicularly. As a result, it can be seen that the active power is only controlled by the pitch angle and tip speed ratio. The previous articles [17; 20; 21; 22] aim to maximize the total active power of the wind farm, by which the annual energy production of the wind farm can be maximized. However, the energy production of the wind farm over its lifespan is determined by not only the annual energy production of the wind farm, but also the lifetime of each wind turbine. In this paper, with the aim of maximizing the total energy production of the wind farm across its lifespan, the optimized pitch angle curve and active power curve are generated for each wind turbine. Firstly, the active power, lifetime, and downstream wind speed of each wind turbine are calculated at all the possible pitch angle and tip speed ratios of each wind turbine by exhausted method. Then, the maximum energy production of the wind farm across its lifespan is obtained and the optimal pitch angle and tip seed ratio of each wind turbine is obtained. With the optimized pitch angle and tip speed ratio, the look-up table of the pitch angle curve and active power curve implemented in the wind turbine controller are generated. The remaining part of this paper is organized as follows: the MPPT method, the Katic wake model, and the lifetime estimation of the wind turbine are addressed and described in Section 2. The method to Maximize Power Generation (MPG) of the wind farm is presented in Section 3. The energy production of the wind farm is compared between the MPPT method and the MPG method in Section 4 by considering their corresponding lifespan. Afterwards, the method to Maximize Energy Production (MEP) of the wind farm is proposed and illustrated in Section 5. Finally, concluding remarks are drawn in Section 6.