The implementation of image-based phenotyping systems has become an important aspect of crop and plant science research which has shown tremendous growth over the years. Accurate determination of features using images...The implementation of image-based phenotyping systems has become an important aspect of crop and plant science research which has shown tremendous growth over the years. Accurate determination of features using images requires stable imaging and very precise processing. By installing a camera on a mechanical arm driven by motor, the maintenance of accuracy and stability becomes non-trivial. As per the state-of-the-art, the issue of external camera shake incurred due to vibration is a great concern in capturing accurate images, which may be induced by the driving motor of the manipulator. So, there is a requirement for a stable active controller for sufficient vibration attenuation of the manipulator. However, there are very few reports in agricultural practices which use control algorithms. Although, many control strategies have been utilized to control the vibration in manipulators associated to various applications, no control strategy with validated stability has been provided to control the vibration in such envisioned agricultural manipulator with simple low-cost hardware devices with the compensation of non-linearities. So, in this work, the combination of proportional-integral-differential(PID) control with type-2 fuzzy logic(T2-F-PID) is implemented for vibration control. The validation of the controller stability using Lyapunov analysis is established. A torsional actuator(TA) is applied for mitigating torsional vibration, which is a new contribution in the area of agricultural manipulators. Also, to prove the effectiveness of the controller, the vibration attenuation results with T2-F-PID is compared with conventional PD/PID controllers, and a type-1 fuzzy PID(T1-F-PID) controller.展开更多
Generally,voltage support at the point of common coupling(PCC)of a wind farm is achieved through centralized static var generators(SVGs).Since the reactive power requirements occupy their capacity in a steady state,th...Generally,voltage support at the point of common coupling(PCC)of a wind farm is achieved through centralized static var generators(SVGs).Since the reactive power requirements occupy their capacity in a steady state,the reactive power support capacity of the SVG is limited during high voltage ride through(HVRT)or low voltage ride through(LVRT).While wind turbines can provide voltage support in accordance with the grid code,their responses are usually delayed due to communication and transmission lags.To enhance the dynamic performance of wind farms during fault ride-through,a reactive power substitution(RPS)control strategy is proposed in this paper.In a steady state,this RPS control method preferentially utilizes the remaining capacity of wind turbines to substitute for the output of the SVG.Considering differences in terminal voltage characteristics and operating conditions,this RPS control method employs a particle swarm optimization(PSO)algorithm to ensure that wind turbines can provide their optimal reactive power support capacity.When the grid voltage swells or drops,the SVG has a sufficient reactive power reserve to support the grid quickly.This paper utilizes a regional power grid incorporating two wind farms connected to different buses as a case study to validate this RPS control strategy.展开更多
As the power control technology of wind farms develops,the output power of wind farms can be constant,which makes it possible for wind farms to participate in power system restoration.However,due to the uncertainty of...As the power control technology of wind farms develops,the output power of wind farms can be constant,which makes it possible for wind farms to participate in power system restoration.However,due to the uncertainty of wind energy,the actual output power can’t reach a constant dispatch power in all time intervals,resulting in uncertain power sags which may induce the frequency of the system being restored to go outside the security limits.Therefore,it is necessary to optimize the dispatch of wind farms participating in power system restoration.Considering that the probability distribution function(PDF)oftransient power sags is hard to obtain,a robust optimization model is proposed in this paper,which can maximize the output power of wind farms participating in power system restoration.Simulation results demonstrate that the security constraints of the restored system can be kept within security limits when wind farm dispatch is optimized by the proposed method.展开更多
文摘The implementation of image-based phenotyping systems has become an important aspect of crop and plant science research which has shown tremendous growth over the years. Accurate determination of features using images requires stable imaging and very precise processing. By installing a camera on a mechanical arm driven by motor, the maintenance of accuracy and stability becomes non-trivial. As per the state-of-the-art, the issue of external camera shake incurred due to vibration is a great concern in capturing accurate images, which may be induced by the driving motor of the manipulator. So, there is a requirement for a stable active controller for sufficient vibration attenuation of the manipulator. However, there are very few reports in agricultural practices which use control algorithms. Although, many control strategies have been utilized to control the vibration in manipulators associated to various applications, no control strategy with validated stability has been provided to control the vibration in such envisioned agricultural manipulator with simple low-cost hardware devices with the compensation of non-linearities. So, in this work, the combination of proportional-integral-differential(PID) control with type-2 fuzzy logic(T2-F-PID) is implemented for vibration control. The validation of the controller stability using Lyapunov analysis is established. A torsional actuator(TA) is applied for mitigating torsional vibration, which is a new contribution in the area of agricultural manipulators. Also, to prove the effectiveness of the controller, the vibration attenuation results with T2-F-PID is compared with conventional PD/PID controllers, and a type-1 fuzzy PID(T1-F-PID) controller.
基金supported in part by the National Natural Science Foundation of China under Grant U2166601 and 51977163.
文摘Generally,voltage support at the point of common coupling(PCC)of a wind farm is achieved through centralized static var generators(SVGs).Since the reactive power requirements occupy their capacity in a steady state,the reactive power support capacity of the SVG is limited during high voltage ride through(HVRT)or low voltage ride through(LVRT).While wind turbines can provide voltage support in accordance with the grid code,their responses are usually delayed due to communication and transmission lags.To enhance the dynamic performance of wind farms during fault ride-through,a reactive power substitution(RPS)control strategy is proposed in this paper.In a steady state,this RPS control method preferentially utilizes the remaining capacity of wind turbines to substitute for the output of the SVG.Considering differences in terminal voltage characteristics and operating conditions,this RPS control method employs a particle swarm optimization(PSO)algorithm to ensure that wind turbines can provide their optimal reactive power support capacity.When the grid voltage swells or drops,the SVG has a sufficient reactive power reserve to support the grid quickly.This paper utilizes a regional power grid incorporating two wind farms connected to different buses as a case study to validate this RPS control strategy.
基金supported by the National Natural Science Foundation of China(No.51507080)the Science and Technology Project of State Grid Corporation of China(5228001600DT)
文摘As the power control technology of wind farms develops,the output power of wind farms can be constant,which makes it possible for wind farms to participate in power system restoration.However,due to the uncertainty of wind energy,the actual output power can’t reach a constant dispatch power in all time intervals,resulting in uncertain power sags which may induce the frequency of the system being restored to go outside the security limits.Therefore,it is necessary to optimize the dispatch of wind farms participating in power system restoration.Considering that the probability distribution function(PDF)oftransient power sags is hard to obtain,a robust optimization model is proposed in this paper,which can maximize the output power of wind farms participating in power system restoration.Simulation results demonstrate that the security constraints of the restored system can be kept within security limits when wind farm dispatch is optimized by the proposed method.
