Abstract
Wake effects impose significant aerodynamic interactions among wind turbines. To improve the wind farm operating performance, practical wind farm online control considering wake effects becomes very important. To achieve online optimal wind farm control while responding to grid demands, this paper proposes a novel optimal wind farm supervisory control (SC) model and its explicit solutions. From the controller modelling perspective, the two major wind farm operating modes, the maximum power point tracking mode and the set-point tracking mode, are first analysed and unified in one optimisation model while considering wake effects. In this way, wind farm power production and rotor kinetic energy reserve can be simultaneously considered to conveniently modify the operation mode in response to different grid demands. Aside from controller modelling, the collocation method is first introduced to address the online application problem of such wake-effect aware optimal WF control. Although a few optimisation algorithms have been proposed to find the optimum offline, online optimal control is still challenging because of the computational complexity brought by wake model non-linearity and non-convexity. The proposed collocation method explicitly approximates the optimal solutions to the proposed supervisory control model, through which only a direct algebraic operation is required for online optimal control instead of repeated optimisations. Case studies are carried out on different wind farms under various wind conditions, showing that the wind farm power production potential and releasable power reserve are improved compared to traditional greedy control in both modes. The accuracy of the collocation method is verified. A detailed analysis of the wind farm production capacity under different wind speeds and directions is also provided.
Highlights
Alleviating the wake effect and satisfactorily integrating wind farms (WFs) into the electricity grid are two considerable challenges in the science of wind energy [1]
Via collocation method (CM), the online optimal WF control problem is switched from repeated optimisation (8)–(15) to explicit algebraic operation (16), which is suitable for online control
This paper proposes an wake-effect aware online optimal WF supervisory control (SC) model
Summary
Alleviating the wake effect and satisfactorily integrating wind farms (WFs) into the electricity grid are two considerable challenges in the science of wind energy [1]. References [10], [17] proposed an optimal WF SC model for the set-point tracking mode, which explicitly integrating the wake equations in rotor kinetic energy optimisation. To provide different services in response to grid demands, both power production and rotor kinetic energy should be simultaneously considered in the WF supervisory control model [16], [18]. The two distinct WF operating modes, MPPT and set-point tracking mode, are first optimised in one unified optimization model In this way, both power production and rotor kinetic energy are simultaneously considered and coordinated and the WF can optimise the operating modes in response to different grid demands.
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