The Experts below are selected from a list of 591 Experts worldwide ranked by ideXlab platform
Dongmei Chen - One of the best experts on this subject based on the ideXlab platform.
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Maximizing Wind Energy Capture for Speed-Constrained Wind Turbines During Partial Load Operation
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 2016Co-Authors: Victor Yu, Mohamed L. Shaltout, Matthew K. Chu Cheong, Dongmei ChenAbstract:With the development of wind turbine technology, more wind turbines operate in the Partial Load region, where one of the main objectives is to maximize captured wind energy. This paper presents the development of an optimal control framework to maximize wind energy capture for wind turbines with limited rotor speed ranges. Numerical optimal control (NOC) techniques were applied to search for the achievable maximum power coefficient, thus maximum wind energy capture. Augmentations of these optimal techniques significantly reduced the computational cost. Simulation results show that, in comparison with the traditional torque feedback and conventional optimal control algorithms, the proposed augmented optimal control algorithm increases the harvested energy while minimizing the computational expense for speed-constrained wind turbines during Partial Load Operation.
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An Adaptive Wind Turbine Controller Considering Both the System Performance and Fatigue Loading
Journal of Dynamic Systems Measurement and Control-transactions of The Asme, 2015Co-Authors: Zheren Ma, Mohamed L. Shaltout, Dongmei ChenAbstract:Wind energy is a clean and renewable source for electricity generation. To reduce the costs associated with wind power generation, development of a control methodology that maximizes the wind energy capture and mitigates the turbine fatigue Loading is desired. In this paper, a new adaptive gain modified optimal torque controller (AGMOTC) for wind turbine Partial Load Operation is presented. A gain-scheduling technique with an internal proportional integral (PI) control is developed to accelerate the controller's convergence to a reference tip speed ratio (TSR). The reference TSR is then adjusted to its optimal value in real-time through an adaptive algorithm capable of rejecting model uncertainties and estimation errors of the control gain. A fatigue mitigation method is also designed to reduce the impact of exacerbated tower bending moments due to the resonance effect. The proposed AGMOTC is evaluated based on the National Renewable Energy Laboratory (NREL) 5 MW wind turbine model using the NREL fast simulator. Simulation results have shown that the AGMOTC has improved efficiency and robustness in wind energy capture and reduced tower fatigue Loading as compared to the traditional control technique.
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Optimal Region 2 Operation of a distributed wind turbine with time-varying weightings to smooth torque variation
2015 American Control Conference (ACC), 2015Co-Authors: Dongmei ChenAbstract:Maximizing energy capture during wind turbine Operation plays a crucial role in increasing wind energy's economic viability and its penetration in the grid. Variable speed Operation enables the turbine to extract more energy during Partial Load Operation or Region 2 Operation. Various control algorithms have been developed to maximize the benefit of using variable ratio Operation. However, the existing control methods cannot provide the knowledge of the maximum wind energy that can be captured and the efficiency gap between an optimal control design and these methods. Therefore, it is necessary to explore the application of optimal control methods. This paper presents a numerical optimal control (NOC) technique to maximize wind energy capture for Region 2 Operation of a wind turbine system. Mitigating turbine torque variation, thus reducing the fatigue Loading of a turbine drivetrain, is also considered in the control design. Furthermore, an approach of incorporating time-varying weightings into developing the optimal controller is introduced to seek further improvement on turbine torque reduction. The performance of the proposed control technique is compared to traditional control strategies in a simulation environment.
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ACC - Optimal Region 2 Operation of a distributed wind turbine with time-varying weightings to smooth torque variation
2015 American Control Conference (ACC), 2015Co-Authors: Dongmei ChenAbstract:Maximizing energy capture during wind turbine Operation plays a crucial role in increasing wind energy's economic viability and its penetration in the grid. Variable speed Operation enables the turbine to extract more energy during Partial Load Operation or Region 2 Operation. Various control algorithms have been developed to maximize the benefit of using variable ratio Operation. However, the existing control methods cannot provide the knowledge of the maximum wind energy that can be captured and the efficiency gap between an optimal control design and these methods. Therefore, it is necessary to explore the application of optimal control methods. This paper presents a numerical optimal control (NOC) technique to maximize wind energy capture for Region 2 Operation of a wind turbine system. Mitigating turbine torque variation, thus reducing the fatigue Loading of a turbine drivetrain, is also considered in the control design. Furthermore, an approach of incorporating time-varying weightings into developing the optimal controller is introduced to seek further improvement on turbine torque reduction. The performance of the proposed control technique is compared to traditional control strategies in a simulation environment.
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Optimal Real-Time Control of Wind Turbine During Partial Load Operation
IEEE Transactions on Control Systems Technology, 2015Co-Authors: Z.y. Ma, Mohamed L. Shaltout, Zeyu Yan, Dongmei ChenAbstract:A wind turbine achieves its highest energy efficiency during Partial Load Operation when it operates at the optimal tip speed ratio (TSR), thus the optimal power coefficient. In this paper, real-time controllers are developed to improve the performance of tracking the optimal TSR during Partial Load Operation. Dynamic programming (DP) is first applied to determine the control actions that maximize wind energy capture. A DP-based real-time controller (DPRC) is then explored to overcome the high computational expense associated with DP, which limits DP to be an offline optimization algorithm. However, the DPRC is not robust against plant-model mismatch and model uncertainties. A gain-modified optimal torque controller (GMOTC) is subsequently designed as an alternative to the DPRC. The GMOTC applies internal Proportional-Integral technique to track a reference TSR, and adapts the reference TSR to the optimal TSR in real time to improve the controller robustness. The light detection and ranging technology is used to further strengthen the controller performance by providing reliable previewed wind speed measurements. Simulation results show that the DRPC generates more wind power than the standard torque controller (STC), while the GMOTC demonstrates a performance similar to that of the DRPC on wind power generation with much better robustness in the presence of modeling error. Fatigue Loading on a wind turbine is another important issue that needs to be considered during control design. The analysis shows that both the DRPC and the GMOTC are comparable with the STC in generating variable torsional Loads due to the torque commands.
John F. Hall - One of the best experts on this subject based on the ideXlab platform.
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Variable Twist Blade Transformation to Improve Wind Turbine Performance
Volume 6B: Energy, 2018Co-Authors: Hamid Khakpour Nejadkhaki, John F. HallAbstract:A concept for an innovative wind turbine blade with an actively transformable twist distribution is presented. A simulation model demonstrates that adapting the blade twist distribution can increase the aerodynamic efficiency during Partial-Load Operation. A blade concept consisting of a rigid spar that is surrounded by deformable modular shells is also proposed. The outer shells are assumed to be produced using additive manufacturing (AM) technology. Integrated features enabled by the AM process tune the stiffness, and thus the degree of flexibility for each surrounding segment. The unique local stiffness and the placement of actuators establishes a nonlinear twist angle distribution (TAD). An optimal design procedure is devised for setting the stiffness and actuator locations. It maximizes the aerodynamic efficiency for a discrete range of wind speed. The blade performance is quantified using data acquired from the National Renewable Energy Laboratory (NREL) Aerodyn software. A computer cluster is used to facilitate this process. It must consider the TAD for the range of wind speed that corresponds to the Partial-Load Operation. The design procedure first establishes the TAD geometry based on the theoretical aerodynamic modeling. The TAD geometry is then passed to a mechanical design algorithm. At this point, the actuator positions are set, and the stiffness ratios of the adaptable shells are defined using the objective function. It minimizes the amount of deviation between the actual TAD and that found in the aerodynamic analysis. The free-shape TAD is determined in the final step. This is the shape of the blade when no actuation force is applied to the shells. This shape is then selected to minimize the amount of deflection needed to shape the TAD between its extreme positions. A case study demonstrates the ability of the blade and the proposed design process. The study indicates that a blade with five actuators can achieve the full range of TAD motion. The final solution shows that the adaptive TAD can increase the efficiency by 3.8 and 3.3%, respectively, at the cut-in and rated speeds.
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Integrative Modeling Platform for Design and Control of an Adaptive Wind Turbine Blade
Volume 2: Control and Optimization of Connected and Automated Ground Vehicles; Dynamic Systems and Control Education; Dynamics and Control of Renewabl, 2018Co-Authors: Hamid Khakpour Nejadkhaki, John F. Hall, Minghui Zheng, Teng WuAbstract:A platform for the engineering design, performance, and control of an adaptive wind turbine blade is presented. This environment includes a simulation model, integrative design tool, and control framework. The authors are currently developing a novel blade with an adaptive twist angle distribution (TAD). The TAD influences the aerodynamic Loads and thus, system dynamics. The modeling platform facilitates the use of an integrative design tool that establishes the TAD in relation to wind speed. The outcome of this design enables the transformation of the TAD during Operation. Still, a robust control method is required to realize the benefits of the adaptive TAD. Moreover, simulation of the TAD is computationally expensive. It also requires a unique approach for both Partial and full-Load Operation. A framework is currently being developed to relate the TAD to the wind turbine and its components. Understanding the relationship between the TAD and the dynamic system is crucial in the establishment of real-time control. This capability is necessary to improve wind capture and reduce system Loads. In the current state of development, the platform is capable of maximizing wind capture during Partial-Load Operation. However, the control tasks related to Region 3 and Load mitigation are more complex. Our framework will require high-fidelity modeling and reduced-order models that support real-time control. The paper outlines the components of this framework that is being developed. The proposed platform will facilitate expansion and the use of these required modeling techniques. A case study of a 20 kW system is presented based upon the Partial-Load Operation. The study demonstrates how the platform is used to design and control the blade. A low-dimensional aerodynamic model characterizes the blade performance. This interacts with the simulation model to predict the power production. The design tool establishes actuator locations and stiffness properties required for the blade shape to achieve a range of TAD configurations. A supervisory control model is implemented and used to demonstrate how the simulation model blade performs in the case study.
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A design methodology for selecting ratios for a variable ratio gearbox used in a wind turbine with active blades
Renewable Energy, 2018Co-Authors: Hamid Khakpour Nejadkhaki, Swanil Chaudhari, John F. HallAbstract:This paper investigates the performance of a variable ratio gearbox (VRG) used in a small fixed-speed wind turbine with active blades. The major components of the VRG-enabled drivetrain are an automatic-manual gearbox and squirrel cage induction generator that connects directly to the grid. The simplicity of this system may be appealing for applications when cost and reliability are of concern. It is an alternative to variable speed systems, which necessitate a modified generator and power conditioning equipment. During Partial Load Operation the VRG provides a discrete set of rotor speeds. This allows the controller to track the wind speed and to achieve a greater efficiency. This study suggests three VRG ratios are sufficient to improve performance when used with active blades. A case study is presented where the performance is simulated using three different wind data sets. The study suggests that the VRG can improve production between 7 and 8.5% in low wind areas. The design procedure also illustrates a technique for finding the lowest and highest gear ratios needed for VRG design. These ratios allow the system to achieve the lowest cut-in and rated speeds. The approach also has useful implications for the design of a continuously variable transmission.
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Wind energy conversion with a variable-ratio gearbox: design and analysis
Renewable Energy, 2011Co-Authors: John F. Hall, Dongmei Chen, Christine A. Mecklenborg, Siddharth B. PratapAbstract:Variable-speed wind turbines are able to adapt to low wind speeds and therefore have greater efficiency than fixed-speed turbines during Partial-Load Operation. Unfortunately, the high cost and low reliability of the electronics that enable variation in speed have discouraged this mode of Operation for distributed wind turbines. Alternatively, a Variable-Ratio Gearbox (VRG) can be integrated into the fixed-speed wind turbine to facilitate Operation with a discrete set of variable speeds that boost efficiency. The VRG concept is based upon mature technology taken from the automotive industry and is characterized by low cost and high reliability. In this paper, a model-based design methodology is introduced to study the performance gain of integrating a VRG into a fixed-speed stall-regulated wind turbine system. The results demonstrate how this device can improve the efficiency of the fixed-speed turbine in the Partial-Load region and the potential to use the VRG to limit power in the full-Load region where pitch control is often used.
F Scala - One of the best experts on this subject based on the ideXlab platform.
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performance analyses of a spark ignition engine firing with gasoline butanol blends at Partial Load Operation
Energy Conversion and Management, 2016Co-Authors: E Galloni, G Fontana, S Staccone, F ScalaAbstract:Biofuels seem to represent one of the most promising means for the limitation of the greenhouse gas emissions coming from traditional energy systems. In this paper, the performance of a “downsized” spark-ignition engine, fueled by gasoline and bio-butanol blends (20% and 40% butanol mass percentage), has been analyzed. In the first phase of this activity, the experimental tests have been carried out at operating points ranging from low to medium engine speed and Load. The first investigations were aimed to assess the main differences among the different fuels in terms of output torque, thermal efficiency, combustion duration and optimal spark timing. In order to study the engine behavior in a wide range of fuel mixtures, these parameters have been evaluated for equivalence ratio values ranging from 1.25 to 0.83. The results obtained in this step show that both the engine torque and thermal efficiency slightly decrease (meanly about 4%) when the blend alcohol content increases. However, butanol increases the burning rate of lean mixtures and an interesting result is that the spark advance does not require adjustments when fueling changes from neat gasoline to bio-butanol/gasoline blends. Later, the pollutant emissions and the CO2 emissions, for both rich and lean mixtures of pure gasoline and gasoline bio-butanol blends, have been measured. In general, firing with alcohol blends, NOx and CO emissions remain quite the same, HC emissions slightly decrease while the CO2 emissions slightly increase. At the end, in order to reproduce the real world urban driving cycle, stoichiometric mixtures have been analyzed. In these conditions, the engine thermal efficiency, at given speed and torque, has been evaluated for each kind of fueling. The results obtained in these operating points have shown that the alcohol blend fueling performs an efficiency penalty less than 2 percent.
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Performance analyses of a spark-ignition engine firing with gasoline–butanol blends at Partial Load Operation
Energy Conversion and Management, 2016Co-Authors: E Galloni, G Fontana, S Staccone, F ScalaAbstract:Biofuels seem to represent one of the most promising means for the limitation of the greenhouse gas emissions coming from traditional energy systems. In this paper, the performance of a “downsized” spark-ignition engine, fueled by gasoline and bio-butanol blends (20% and 40% butanol mass percentage), has been analyzed. In the first phase of this activity, the experimental tests have been carried out at operating points ranging from low to medium engine speed and Load. The first investigations were aimed to assess the main differences among the different fuels in terms of output torque, thermal efficiency, combustion duration and optimal spark timing. In order to study the engine behavior in a wide range of fuel mixtures, these parameters have been evaluated for equivalence ratio values ranging from 1.25 to 0.83. The results obtained in this step show that both the engine torque and thermal efficiency slightly decrease (meanly about 4%) when the blend alcohol content increases. However, butanol increases the burning rate of lean mixtures and an interesting result is that the spark advance does not require adjustments when fueling changes from neat gasoline to bio-butanol/gasoline blends. Later, the pollutant emissions and the CO2 emissions, for both rich and lean mixtures of pure gasoline and gasoline bio-butanol blends, have been measured. In general, firing with alcohol blends, NOx and CO emissions remain quite the same, HC emissions slightly decrease while the CO2 emissions slightly increase. At the end, in order to reproduce the real world urban driving cycle, stoichiometric mixtures have been analyzed. In these conditions, the engine thermal efficiency, at given speed and torque, has been evaluated for each kind of fueling. The results obtained in these operating points have shown that the alcohol blend fueling performs an efficiency penalty less than 2 percent.
Zhichao Chen - One of the best experts on this subject based on the ideXlab platform.
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Influence of different oil feed rate on bituminous coal ignition in a full-scale tiny-oil ignition burner
Frontiers in energy, 2013Co-Authors: Zhengqi Li, Qiudong Zong, Xiang Zhang, Zhichao ChenAbstract:To reduce oil consumption during firing-up and Partial-Load Operation, a tiny-oil ignition burner has been recommended. Through reacting-flow experiments performed on a full-scale experimental setup, the influence of different oil flow rates on bituminous coal combustion as well as flow rates without coal feed was analyzed. The ignition burner is identical to that normally used in an 800 MWe utility boiler. Under operating conditions with flow rates of 50, 100, and 150 kg/h, gas temperature distributions were measured in the burner. At the equivalent measuring points at the exits of the first and second combustion chambers, these distributions remained almost unchanged under a constant coal feed rate of 4 t/h. However on the burner centerline, distributions increased slightly with increasing flow rate. Different gas concentrations were measured at the center of the burner exit. For instance, the O2 concentration at the burner exit varied from 0.01% to 0.31% whereas CO concentrations were more than 10000 ppm. At the same coal feed rate of 4 t/h, burner resistances are 480, 600, and 740 Pa for oil flow rates of 50, 100, and 150 kg/h, respectively.
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Bituminous coal combustion in a full-scale start-up ignition burner: Influence of the excess air ratio
Energy, 2010Co-Authors: Zhengqi Li, Yang Zhao, Weiguang Kong, Zhichao ChenAbstract:A start-up ignition burner has been proposed to reduce oil fuel consumption during the firing-up process and Partial-Load Operation. To investigate the influence of different excess air ratios on bituminous coal combustion in the start-up ignition burner, full-scale reacting-flow experiments were performed for an experiment setup. The ignition burner was identical to that normally used in an 800 MWe utility boiler. Gas temperature distributions in the burner were obtained for excess air ratios of 0.56, 0.75, 0.98 and 1.14 (corresponding to primary air velocities of 17, 23, 30 and 35 m/s). Coal burnout and the release of C and H were observed at the exit of the burner nozzle. Gases such as O2 and CO were measured at the center of the burner. A change in resistance was obtained within the burner.
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Experimental Studies on the Effect of the Pulverized Coal Concentration on Lean-Coal Combustion in a Lateral-Ignition Tiny-Oil Burner
Energy & Fuels, 2010Co-Authors: Zhengqi Li, Yang Zhao, Weiguang Kong, Zhichao ChenAbstract:Because of the low volatile content and high ignition temperature of lean coal, it is difficult to employ tiny-oil ignition technology in the firing up and Partial-Load Operation of a pulverized-coal-fired boiler. To investigate the influence of the coal concentration on lean-coal combustion in a lateral-ignition tiny-oil burner, full-scale reacting-flow experiments were performed using an experimental setup. As the coal concentration increased from 0.27 to 0.80 kg (corresponding to a coal feed rate increasing from 1.5 to 4.5 tons/h), the gas temperatures at the burner center line and 116.5 mm from the burner center line (10 mm from the burner wall) decreased gradually at equivalent measuring points. The gas temperatures on the side with oil guns were higher than those on the opposite side for the same distances from the burner exit. O2 concentrations at the exit of the burner were 0.41−3.64%. The burner resistance resulting from the flow and combustion of pulverized coal was 1400−2200 Pa. Increasing the ...
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Influence of the Coal Feed Rate on Lean Coal Ignition in a Full-Scale Tiny-Oil Ignition Burner
Energy & Fuels, 2010Co-Authors: Zhengqi Li, Yang Zhao, Zhichao ChenAbstract:A tiny-oil ignition burner was proposed to reduce oil consumption in firing up and Partial-Load Operation. To investigate the influence of the feed rate on lean coal ignition in the tiny-oil igniti...
E Galloni - One of the best experts on this subject based on the ideXlab platform.
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performance analyses of a spark ignition engine firing with gasoline butanol blends at Partial Load Operation
Energy Conversion and Management, 2016Co-Authors: E Galloni, G Fontana, S Staccone, F ScalaAbstract:Biofuels seem to represent one of the most promising means for the limitation of the greenhouse gas emissions coming from traditional energy systems. In this paper, the performance of a “downsized” spark-ignition engine, fueled by gasoline and bio-butanol blends (20% and 40% butanol mass percentage), has been analyzed. In the first phase of this activity, the experimental tests have been carried out at operating points ranging from low to medium engine speed and Load. The first investigations were aimed to assess the main differences among the different fuels in terms of output torque, thermal efficiency, combustion duration and optimal spark timing. In order to study the engine behavior in a wide range of fuel mixtures, these parameters have been evaluated for equivalence ratio values ranging from 1.25 to 0.83. The results obtained in this step show that both the engine torque and thermal efficiency slightly decrease (meanly about 4%) when the blend alcohol content increases. However, butanol increases the burning rate of lean mixtures and an interesting result is that the spark advance does not require adjustments when fueling changes from neat gasoline to bio-butanol/gasoline blends. Later, the pollutant emissions and the CO2 emissions, for both rich and lean mixtures of pure gasoline and gasoline bio-butanol blends, have been measured. In general, firing with alcohol blends, NOx and CO emissions remain quite the same, HC emissions slightly decrease while the CO2 emissions slightly increase. At the end, in order to reproduce the real world urban driving cycle, stoichiometric mixtures have been analyzed. In these conditions, the engine thermal efficiency, at given speed and torque, has been evaluated for each kind of fueling. The results obtained in these operating points have shown that the alcohol blend fueling performs an efficiency penalty less than 2 percent.
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Performance analyses of a spark-ignition engine firing with gasoline–butanol blends at Partial Load Operation
Energy Conversion and Management, 2016Co-Authors: E Galloni, G Fontana, S Staccone, F ScalaAbstract:Biofuels seem to represent one of the most promising means for the limitation of the greenhouse gas emissions coming from traditional energy systems. In this paper, the performance of a “downsized” spark-ignition engine, fueled by gasoline and bio-butanol blends (20% and 40% butanol mass percentage), has been analyzed. In the first phase of this activity, the experimental tests have been carried out at operating points ranging from low to medium engine speed and Load. The first investigations were aimed to assess the main differences among the different fuels in terms of output torque, thermal efficiency, combustion duration and optimal spark timing. In order to study the engine behavior in a wide range of fuel mixtures, these parameters have been evaluated for equivalence ratio values ranging from 1.25 to 0.83. The results obtained in this step show that both the engine torque and thermal efficiency slightly decrease (meanly about 4%) when the blend alcohol content increases. However, butanol increases the burning rate of lean mixtures and an interesting result is that the spark advance does not require adjustments when fueling changes from neat gasoline to bio-butanol/gasoline blends. Later, the pollutant emissions and the CO2 emissions, for both rich and lean mixtures of pure gasoline and gasoline bio-butanol blends, have been measured. In general, firing with alcohol blends, NOx and CO emissions remain quite the same, HC emissions slightly decrease while the CO2 emissions slightly increase. At the end, in order to reproduce the real world urban driving cycle, stoichiometric mixtures have been analyzed. In these conditions, the engine thermal efficiency, at given speed and torque, has been evaluated for each kind of fueling. The results obtained in these operating points have shown that the alcohol blend fueling performs an efficiency penalty less than 2 percent.