This article investigates the impact of the pitch-to-stall and pitch-to-feather control concepts on horizontal axis wind turbines (HAWTs) with different blade designs. Pitch-to-feather control is widely used to limit the power output of wind turbines in high wind speed conditions. However, stall control has not been taken forward in the industry because of the low predictability of stalled rotor aerodynamics. Despite this drawback, this article investigates the possible advantages of this control concept when compared to pitch-to-feather control with an emphasis on the control performance and its impact on the pitch mechanism and structural loads. In this study, three HAWTs with different blade designs, i.e., untwisted, stall-regulated, and pitch-regulated blades, are investigated. The control system is validated in both uniform and turbulent wind speed. The results show that pitch-to-stall control enhances the constant power control for wind turbines with untwisted and stall-regulated blade designs. Stall control alleviates the fore-aft tower loading and the blades flapwise moment of the wind turbine with stall-regulated blades in uniform winds. However, in turbulent winds, the flapwise moment increases to a certain extent as compared to pitch-to-feather control. Moreover, pitch-to-stall control considerably reduces the summed blade pitch movement, despite that it increases the risk of surface damage in the rolling bearings due to oscillating movements with a small amplitude.

The components of an operational wind turbine are continuously impacted by both static and dynamic loads. Regular inspections and maintenance are required to keep these components healthy. The main bearing of a wind turbine is one such component that experiences heavy loading forces during operation. These forces depend on various parameters such as wind speed, operating regime and control actions. When a wind turbine provides frequency containment reserve (FCR) to support the grid frequency, the forces acting upon the main bearing are also expected to exhibit more dynamic variations. These forces have a direct impact on the lifetime of the main bearing. With an increasing trend of wind turbines participating in the frequency ancillary services market, an analysis of these dynamic forces becomes necessary. To this end, this paper assesses the effect of FCR-based control on the main bearing lifetime of the wind turbine. Firstly, a control algorithm is implemented such that the output power of the wind turbine is regulated as a function of grid frequency and the amount of FCR. Simulations are performed for a range of FCR to study the changing behaviour of dynamical forces acting on the main bearing with respect to the amount of FCR provided. Then, based on the outputs from these simulations and using 2 years of LiDAR wind data, the lifetime of the main bearing of the wind turbine is calculated and compared for each of the cases. Finally, based on the results obtained from this study, the impact of FCR provision on the main bearing lifetime is quantified and recommendations are made, that could be taken into account in the operation strategy of a wind farm.

The participation of wind farms in providing ancillary services is an asset for the power system and one way to maintain a strong grid with the increasing penetration of renewable energy sources. Research has shown this to be feasible for wind farms by using efficient prediction and sophisticated control systems. In some parts of the world, strict grid codes are already being implemented that require wind farms to provide ancillary services. Moreover, the primary reserve market in Europe is moving towards shorter procurement periods, providing wind farms an opportunity to more efficiently optimise their resources based on short term forecasts. It can however be challenging for the wind farms to efficiently participate in grid frequency support services, especially for primary reserve services. The reason behind this is the requirement of quick activation and deactivation of power reserve margin for services such as Frequency Containment Reserve (FCR) and Fast Frequency Response (FFR). A full activation of the contracted reserve is required within seconds of a grid frequency dip. A sudden change in wind turbine dynamics is expected to have an impact on the wake behind the wind turbine. The wake effect within a wind farm is taken into thorough consideration in its design process. The effect on the wake due to the wind turbines participating in fast response ancillary services however, remains unexplored. This is a matter of greater concern for wind farms with a high capacity density. To this end, the main contribution of this article is to observe the effect of ancillary service based control system on the wake effect of a wind turbine. Additionally, the capability of developed wind turbines controllers to follow primary reserve services are also tested. FFR and FCR services are tested for a range of frequency designs, these include both synthetic and actual grid frequencies. The synthetic frequency profiles are designed to replicate both fast and slow frequency variations in order to analyse the impact on wake behaviour. The simulations are performed for low and high wind speed including constant as well as turbulent winds.

Wind power has emerged as a clean alternative to traditional power production, with a significant increase in its installed capacity observed over the past decade. In numerous regions, wind power producers are now afforded the opportunity to participate in day-ahead energy and reserve markets. In this context, the wind turbines can provide ancillary services such as frequency containment reserve (FCR). However, the provision of ancillary services is known to affect the physical loading on a wind turbine. This loading on different parts of the wind turbine can possibly result in sub-optimal performance leading to a reduced net power output or even a faster degradation of the wind turbine. On the other hand, no or low participation of a wind turbine in ancillary services market will lead to a lesser revenue on a long term. Moreover, low participation of wind turbines in the ancillary market will eventually limit the amount of wind power, since the ancillary services are needed to stabilise the grid and must then be provided by other energy sources. Addressing this challenge requires a holistic method to gauge both load and revenue for wind power producers (WPP), thus enabling them to make informed decisions. This study firstly presents a method of calculating major loads on the wind turbine. Then, a load-aware optimisation method of wind power scheduling in the joint day-ahead energy and reserve market (JERM) is proposed that provides WPPs, an ability to strike a balance between revenue and the physical loading of wind turbine.