Advanced concepts for control of wind turbine and wind farm systems

Although wind turbine technology is comparatively young, with large-scale series production starting in the 1980s, it has reached a high degree of maturity. The early years of wind turbine development saw many iterative improvements, with some proving themselves worthy of further usage; others are now regarded as design experiments. The basic concept has remained mostly unchanged since the mid-1990s: a three-bladed upwind rotor and a variable-speed generator. Turbine operation is controlled to keep the rotor speed at its aerodynamically optimal setpoint below rated power and to limit the power by controlling the pitch angle of the blades to feather. This concept has reached a high degree of perfection. The turbines work autonomously, produce power with low maintenance, and support grid operation.The above-mentioned concept is driven by wind physics and the limits of the selected generator size. Thus, there is a very small margin for further improvements of control regarding the primary objective: power generation. With the mature wind turbine controller technology as a basis, advanced control concepts can put a focus on secondary objectives and wider system scope. With such a wider scope, a single turbine is not an independent operating system serving the primary objective, but it acts as part of a larger system: a full wind farm that is controlled as a whole within the surrounding ecosystem composed of the environment, the market, and the grid. Within this context, the possibilities for advanced control concepts become vast. We give an overview on these possibilities focusing on improving the ecologic impact of wind energy from load-related usage of materials.We start by taking a brief look into the ecological impact of wind energy in Section 9.1, from which we derive potentials for economic, ecologic, and operational improvements by structuring control concepts for these purposes in Section 9.2. With these concepts, we present the architecture for a system-wide control of an entire wind farm in Section 9.3. Within this architecture, operational planning over the entire lifetime is a key concept that combines turbine-level control with global lifetime objectives. Details of an optimal planning approach are presented in Section 9.4. We conclude by summarizing the challenges and required methods for evaluating advanced control concepts in Section 9.5.