Multi-strategy wind farm control: alternating wake steering and helix wake mixing on a large-scale wind farm

Abstract

Abstract. Wind farm flow control mitigates wake effects by adjusting turbine settings to improve overall farm performance rather than the output of each turbine. Wake steering is an established wind farm flow control approach, while the helix method has recently emerged as a promising solution that enhances wake recovery by increasing mixing with the free-stream flow. This study quantifies the value of a combined strategy, in which each turbine can apply wake steering or the helix method. The analysis is performed considering different levels of uncertainty in wind direction, using engineering wake models that enable the simulation of these techniques on large-scale wind farms. A novel optimization algorithm, called multi-strategy serial-refine (MSR), is developed in this study, extending the state-of-the-art yaw-optimization method to include multiple control strategies and a generalized objective. A scaled version of an offshore wind farm in the Netherlands is selected as the case study, consisting of 69 IEA 22 MW turbines. The proposed combined strategy results in a greater increase in annual energy production than either individual strategy, leveraging the effectiveness of the helix method when multiple misaligned downstream turbines are present. This trend persists even under wind direction uncertainty. Due to the high sensitivity of wake steering to such uncertainty, the combined strategy benefits from the superior robustness of the helix method under these conditions.