Wind farm control work at the University of Strathclyde, past, present and future

Stock, Adam and Leithead, William and Anaya-Lara, Olimpo and Amos, Lindsey and Cole, Matthew and Taylor, Peter and Pirrie, Paul and Campos-Gaona, David (2019) Wind farm control work at the University of Strathclyde, past, present and future. In: 5th Wind Energy Systems Engineering Workshop, 2019-10-02 - 2019-10-04.

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    Abstract

    Researchers in the Wind Energy and Control Centre (WECC) at the University of Strathclyde have been working on wind farm modelling and wind farm control (WFC) since 2010, when work began on the Power Adjusting Controller (PAC), an augmentation to wind turbine controllers to allow flexible and accurate control of the turbine power output. The PAC is designed to work within a hierarchical wind farm control structure, a structure that is decentralised and scalable (see Figure 1). In order to design and test wind farm control strategies a wind farm model has been developed known as StrathFarm. StrathFarm uses wind turbine models, developed over the past 20 years, which incorporate lumped parameter models of the drive-train and rotor, aerodynamic modelling that includes induction lag effects, and modelling of blade and tower loads validated against DNV GL’s Bladed. The wind comprises a pre-processed correlated low frequency wind farm wind field, to which higher frequency effective wind field components are added locally to each turbine. Wakes can be modelled in two ways; an engineering model based on the work of Frandsen or a higher fidelity method based on the DTU WFSim model. StrathFarm is uniquely placed in providing a simulation environment that allows medium fidelity simulations modelling turbine dynamics and wakes in turbulent winds to be run in better than real time for wind farms of up to 100 wind turbines. Work is currently ongoing identifying the resolution of power and loading results from StrathFarm, which is key to determining in general the dependence of statistical significance of estimates of wind farm control performance on the length or number of simulations. Using the control hierarchy of Figure 1 and the simulation capacity of StrathFarm, WFC for the provision of ancillary services, namely synthetic inertia, droop control, and curtailment, has been developed. The advantage of the hierarchical structure shown in Figure 1 becomes apparent when implementing these controllers, as the required change in power can be distributed using the distributed controller to minimise the loads on the turbines. As an example, a curtailment strategy has been designed that implements a highly accurate curtailment whilst reducing tower and blade damage equivalent loads (DELs) in all operating conditions. The reduction for tower DELs and blade DELs can be as high as 20% depending on curtailment level and wind conditions. WFC continues to be a key focus of the WECC, with particular interests and current work in: • Using WFC to increase the penetration of wind generation in the UK grid system • Using WFC and storage to reduce the rating of sub-sea inter-connector cables • Coordinate the control of offshore converters and wind turbines in the wind farm to create a virtual power plant • Wind farm based collective yaw control