Browsing by Subject "Energy maximization"
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Item Cost-conscious control strategies for wind turbine systems(2017-05) Ma, Zheren; Chen, Dongmei, Ph. D.; Baldick, Ross; Djurdjanovic, Dragan; Longoria, Raul G.; Barr, RonaldWind energy is one of the most abundant renewable energy sources that can meet future energy demands. Despite its fast growth, wind energy is still a marginal player in electricity generation. The key issues preventing wider deployment of wind turbines include low energy conversion efficiency, high maintenance cost, wind intermittency and unpredictability etc. These issues lead to considerably higher cost of wind power compared to that of traditional power sources. This work is focused on control designs to overcome the above challenges. First, control algorithms are developed for energy capture maximization. During partial load operation, wind turbine rotor speed is continuously adjusted to remain optimal operation by manipulating the electromagnetic torque applied to the generator. In this dissertation, a dynamic programming based real-time controller (DPRC) and a gain modified optimal torque controller (GMOTC) are developed for faster convergence to optimal power operation under volatile wind speed and better robustness against modeling uncertainties. Secondly, fatigue loading mitigation techniques are developed to reduce the maintenance cost of a wind turbine. During partial load operation, a generator torque-based fatigue mitigation method is devised to reduce the impact of exacerbated tower bending moments associated with the resonance effect. During full load operation, a H₂ optimization has been carried out for gain scheduling of a Proportional-Integral blade pitch controller. It improves speed regulation and reduces drivetrain fatigue loading with less oscillations of turbine rotor speed and generator torque. Thirdly, battery energy storage systems (BESS) have been integrated with wind turbines to mitigate wind intermittence and make wind power dispatchable as traditional power sources. Equipped with a probabilistic wind speed forecasting model, a new power scheduling and real-time control approach has been proposed to improve the performance of the integrated system. Finally, control designs are oriented to wind turbine participation in grid primary frequency regulation. The fast active power injection/absorption capability of wind turbine enables it to rapidly change its power output for stablizing the grid frequency following an sudden power imbalance event. In addition to quick response to grid frequency deviation event, the proposed controller guarantees turbine stability with smooth control actions.Item Optimal control of wind turbines for distributed power generation(2015-08) Shaltout, Mohamed Lotfi Eid Nasr; Chen, Dongmei, Ph. D.; Longoria, Raul G.; Crawford, Richard H.; Deshpande, Ashish D.; Malikopoulos, Andreas A.; Pratap, Siddharth B.Wind energy represents one of the major renewable energy sources that can meet future energy demands to sustain our lifestyle. During the last few decades, the installation of wind turbines for power generation has grown rapidly worldwide. Besides utility scale wind farms, distributed wind energy systems contributes to the rise in wind energy penetration. However, the expansion of distributed wind energy systems is faced by major challenges such as the system’s reliability in addition to the environmental impacts. This work is intended to explore various control algorithms to enable the distributed wind energy systems to face the aforementioned challenges. First of all, a stall regulated fixed speed wind turbine augmented with a variable ratio gearbox has been proven to enhance the wind energy capture at a relatively low cost, and considered as an attractive design for small wind energy systems. However, the high reliability advantage of traditional fixed-speed wind turbines can be affected by the integration of the variable ratio gearbox. A portion of this work is intended to develop a control algorithm that extends the variable ratio gearbox service life, thus improves overall system reliability and reduces the expected operational cost. Secondly, a pitch regulated variable speed wind turbines dominates the wind energy industry as it represents a balance between cost and flexibility of operation. They can be used for midsized wind power generation. Optimizing its wind energy capture while maintain high system reliability has been the one of the main focuses of many researchers. Another portion of this work introduces a model predictive control framework that enhances the reliability of pitch regulated variable speed wind turbines, thus improves their operational cost. Finally, one of the major environmental challenges facing the continuous growth of wind energy industry is the noise emitted from wind turbines. The severity of the noise emission problem is more significant for small and medium sized wind turbines installed in the vicinity of residential areas for distributed power generation. Consequently, the last portion of this work is intended to investigate the potential of wind turbine control design to reduce noise emission in different operating conditions with minimal impact on power generation