Xiu-xing Yin

Adaptive sliding mode back-stepping pitch angle control of a variable-displacement pump controlled pitch system for wind turbines.

A variable-displacement pump controlled pitch system is proposed to mitigate generator power and flap-wise load fluctuations for wind turbines. The pitch system mainly consists of a variable-displacement hydraulic pump, a fixed-displacement hydraulic motor and a gear set. The hydraulic motor can be accurately regulated by controlling the pump displacement and fluid flows to change the pitch angle through the gear set. The detailed mathematical representation and dynamic characteristics of the proposed pitch system are thoroughly analyzed. An adaptive sliding mode pump displacement controller and a back-stepping stroke piston controller are designed for the proposed pitch system such that the resulting pitch angle tracks its desired value regardless of external disturbances and uncertainties. The effectiveness and control efficiency of the proposed pitch system and controllers have been verified by using realistic dataset of a 750 kW research wind turbine.

Integrated pitch control for wind turbine based on a novel pitch control system

A novel pitch control system is proposed for wind turbine to smooth output power and load fluctuations. This system is driven by a servo-valve controlled hydraulic motor and is precisely controlled to track the desired pitch angle trajectory. Nonlinear modeling and characteristics of this system are presented and analyzed. An adaptive nonlinear sliding mode pitch angle controller is designed to deal with the uncertainties and external disturbances in this system. An integrated pitch control strategy is proposed to generate the reference pitch commands for this system by considering the load reductions. The proposed system, pitch controller, and the control strategy have been validated for efficient and accurate pitch control performances by comparative experimental results under realistic wind speeds.

Adaptive back-stepping pitch angle control for wind turbine based on a new electro-hydraulic pitch system

A new electro-hydraulic pitch system is proposed to smooth the output power and drive-train torque fluctuations for wind turbine. This new pitch system employs a servo-valve-controlled hydraulic motor to enhance pitch control performances. This pitch system is represented by a state-space model with parametric uncertainties and nonlinearities. An adaptive back-stepping pitch angle controller is synthesised based on this state-space model to accurately achieve the desired pitch angle control regardless of such uncertainties and nonlinearities. This pitch angle controller includes a back-stepping procedure and an adaption law to deal with such uncertainties and nonlinearities and hence to improve the final pitch control performances. The proposed pitch system and the designed pitch angle controller have been validated for achievable and efficient power and torque regulation performances by comparative experimental results under various operating conditions.

Fuzzy-Logic Sliding-Mode Control Strategy for Extracting Maximum Wind Power

A fuzzy-logic sliding-mode control strategy is proposed to capture the maximum wind energy and reduce the generator-side current harmonics for a direct-driven wind power system. The control strategy mainly consists of a fuzzy logic controller for generating the optimum dc-side current and a double integral sliding-mode current controller capable of accurately tracking the optimum dc-side current. A resonant filter is also incorporated into the fuzzy logic controller to eliminate the generator-side current harmonics. Detailed design procedure, existence, and stability conditions of the proposed control strategy have been thoroughly investigated and presented. The capability and effectiveness of the proposed control strategy have been validated by comparative experimental results.

Predictive pitch control of an electro-hydraulic digital pitch system for wind turbines based on the extreme learning machine:

An electro-hydraulic digital pitch system is proposed in this paper to regulate output power and drive-train torque for wind turbines. This pitch system is driven by an electro-hydraulic digital servo system and can be digitally controlled to regulate the blade pitch angle with relatively high control accuracy and fast response. A closed control loop of this pitch system is presented and an extreme learning machine is online trained to represent the nonlinear wind turbine characteristics in this control loop. Furthermore, a predictive pitch controller is designed to improve the final pitch control performances by using the established extreme learning machine. Comparative experimental results are presented to illustrate the achievable significant performance improvements on output power and drive-train torque regulations by using the proposed pitch system and predictive pitch controller.

Operating Modes and Control Strategy for Megawatt-Scale Hydro-Viscous Transmission-Based Continuously Variable Speed Wind Turbines

A megawatt (MW)-scale hydro-viscous transmission-based continuously variable speed wind turbine is proposed to guarantee a smooth transition among different operating regions and hence to improve power efficiency and quality. This turbine is achieved by highly integrating a hydro-viscous element into the turbine drive-train to mitigate the upstream wind-loading fluctuations. This element allows the turbine speed to be directly regulated by continuously changing the oil film thickness in this element. Three important operating modes of this turbine system are proposed. The control-oriented drive-train model is also established and validated based on experimental data. A cooperative control strategy over the full operating range is then proposed based on such modes. A series of comparative cosimulations are carried out to evaluate the stability and effectiveness of the proposed turbine system in speed and power regulations. This proposed system holds several advantages such as large power capacity, high efficiency, downsized power converters, and low cost. Such advantages make this turbine system particularly attractive and promising for medium-to-large-scale wind power applications.

Loading system and control strategy for simulating wind turbine loads

A novel loading control system is proposed to accurately simulate the five-degree-of-freedom loads experienced by a real wind turbine. For this system, the real wind rotor and blades are replaced by an equivalent rotating disc and driven by an electric motor. A set of loading actuators are uniformly placed around this disc and are regulated to accurately create these turbine loads. In this paper, the five-degree-of-freedom turbine loads are defined in blade and hub reference frames. A load-decomposition based loading control strategy is presented to decompose such loads into reference loading forces for each actuator. An axial loading actuator is used for system modeling and analysis. Experimental results have validated that the proposed loading system and control strategy can accurately simulate the representative turbine loads with a good confidence level.