Advanced Research Turbines
The National Wind Technology Center (NWTC) uses two large turbines to conduct advanced controls research. Two 600-kilowatt Westinghouse turbines are used to test new control schemes and equipment for reducing loads on wind turbine components. As today's utility-scale wind turbines become taller to reach wind resources found at greater heights, their structures are becoming more complex and their components more flexible and lighter weight. Novel control mechanisms are necessary to prevent damage to turbines and possible system failures. But wind turbines also must be designed to capture the maximum amount of energy from the wind, so engineers must develop new controls to maximize energy capture and reduce loads. New control mechanisms and computer codes can help the wind turbine shed some loads in extreme or very turbulent winds. Both turbines are specially configured to allow for the analysis of these diverse control schemes.
The GE 1.5-MW wind turbine installed at the NWTC in 2009 is used as a tool for long-term testing and R&D. It has been instrumented to collect detailed data that will help researchers address a variety of issues, including wind farm underperformance and premature turbine component failure.
Controls Advanced Research Turbines
Testing new control schemes on the Controls Advanced Research Turbines (CARTs) is a critical step before new control systems can be implemented in commercial machines.
These two horizontal-axis Westinghouse WTG-600 models were formerly deployed for 10 years in a commercial wind farm in Hawaii. NWTC engineers installed modifications to use the turbines to test new control schemes for reducing loads on wind turbine components.
A new pitch system. The original hydraulically actuated pitch system was replaced with a high-speed electromechanical pitch system that enables high bandwidth independent pitch control of the blades.
A new generation system. The new generation system incorporates power electronics that make it possible to control the turbine in either full variable-speed mode or as a constant-speed machine. The new control system allows almost complete flexibility in the type of control that can be implemented.
Added custom instrumentation. A variety of instrumentation was added to allow a high degree of flexibility in the type of control algorithm that can be implemented.
A three-bladed rotor. The two-bladed rotor on one machine was replaced with a three-bladed rotor to allow researchers to test new control schemes applicable only to three-bladed machines.
The CART research turbines provide engineers with platforms to field test advanced control algorithms. Control algorithms reduce turbine loading by responding to feedback measurements from blade load and tower top acceleration data to reduce the turbines load and increase energy capture. Beyond simple feedback instruments, measurements from special instrumentation, such as Light Detection and Ranging (LIDAR), provide information to use in advanced algorithms that further enhance turbine performance. These advanced algorithms are referred to as feed-forward controls.