To enable distributed PV to adapt to variations in power grid strength and achieve stable grid connection while enhancing operational flexibility,it is essential to configure grid-connected inverters with an integrate...To enable distributed PV to adapt to variations in power grid strength and achieve stable grid connection while enhancing operational flexibility,it is essential to configure grid-connected inverters with an integrated grid-following control mode,allowing smooth switching between GFL and GFM modes.First,impedance models of GFL and GFM PV energy storage VSG systems were established,and grid stability was analyzed.Second,an online impedance identification method based on voltage fluctuation data screening was proposed to enhance the accuracy of impedance identification.Additionally,a PV energy storage GFM/GFL VSG smooth switching method based on current inner loop compensation was introduced to achieve stable grid-connected operation of distributed photovoltaics under changes in strong and weak power grids.Finally,a grid stability analysis was conducted on the multi-machine parallel PV ESS,and a simulation model of a multi-machine parallel PV ESS based on current inner loop compensation was established for testing.Results showed that,compared to using a single GFM or single GFL control for the PV VSG system,the smooth switching method of multi-machine parallel PV ESS effectively suppresses system resonance under variations in power grid strength,enabling adaptive and stable grid-connected operations of distributed PV.展开更多
This article investigates the anti-disturbance and stabilization problems for the nonlinear uncertain permanent magnet synchronous motor(PMSM)with stator voltage saturation and unknown load.A smooth switching mechanis...This article investigates the anti-disturbance and stabilization problems for the nonlinear uncertain permanent magnet synchronous motor(PMSM)with stator voltage saturation and unknown load.A smooth switching mechanism is presented to structure the adaptive integral terminal sliding mode control(SMC)strategy.The control design consists of compensation control and nominal control,which improves the rapidity and accuracy of trajectory tracking.The smooth saturation model based on the error function is applied to approximate the voltage saturation phenomenon.Additionally,to deal with the adverse effects of various unknown disturbances,including model parameter uncertainties and unknown external load disturbances,an improved disturbance observer(DO)is proposed.This observer effectively suppresses the fluctuations caused by fixed gain during the starting period of the system.Finally,the experimental results under different conditions show that the proposed strategy has good tracking and disturbance suppression performances.展开更多
This paper is concerned with a systematic method of smooth switching linear parameter- varying （LPV） controllers design for a morphing aircraft with a variable wing sweep angle. The morphing aircraft is modeled as a...This paper is concerned with a systematic method of smooth switching linear parameter- varying （LPV） controllers design for a morphing aircraft with a variable wing sweep angle. The morphing aircraft is modeled as an LPV system, whose scheduling parameter is the variation rate of the wing sweep angle. By dividing the scheduling parameter set into subsets with overlaps, output feedback controllers which consider smooth switching are designed and the controllers in over- lapped subsets are interpolated from two adjacent subsets. A switching law without constraint on the average dwell time is obtained which makes the conclusion less conservative. Furthermore, a systematic algorithm is developed to improve the efficiency of the controllers design process. The parameter set is divided into the fewest subsets on the premise that the closed-loop system has a desired performance. Simulation results demonstrate the effectiveness of this approach.展开更多
A tilt-rotor aircraft has three flight modes: helicopter mode, airplane mode and conversion mode. Unlike the traditional aircraft, the tilt-rotor aircraft, which combines the characteristics of helicopters and fixed-w...A tilt-rotor aircraft has three flight modes: helicopter mode, airplane mode and conversion mode. Unlike the traditional aircraft, the tilt-rotor aircraft, which combines the characteristics of helicopters and fixed-wing aircraft, is a complex multi-body system with the violent variation of the aerodynamic parameters. For these characteristics, a new smooth switching control scheme is provided for the tilt-rotor aircraft. First, the reference commands for airspeed and nacelle angles are calculated by analyzing the conversion corridor and the conversion path. Subsequently, based on the finite-time switching theorem, an average dwell time condition is designed to guarantee the stability in the switching process. Besides, considering the state vibrations and bumps may appear in switching points, the fuzzy weighted logic is employed to improve the system transient performance. For disturbance rejection, three extended state observers are designed separately to estimate the disturbances in the switched systems. Compared with the traditional auto disturbance rejection control and proportion integration differentiation control, this method overcomes the conservatism of wasting the whole model information. The control performances of robustness and smoothness are verified with simulation, which shows that the new smooth switching control scheme is more targeted and superior than the traditional design method.展开更多
A model reference adaptive control(MRAC)with smooth switching scheme was proposed for piecewise linear systems,and the method was utilized in turbofan engine control to avoid the discontinuity of control input.In this...A model reference adaptive control(MRAC)with smooth switching scheme was proposed for piecewise linear systems,and the method was utilized in turbofan engine control to avoid the discontinuity of control input.In this scheme,each sub-region of the operating envelope had its own MRAC controller,and smooth indicator function based smooth switching scheme was introduced to switch multiple controllers smoothly at the boundary of adjacent sub-regions.The Lyapunov stability analysis indicated that the proposed smooth switching scheme can guarantee the convergence of the closed-loop system during the controllers switching.The tracking error system was converted into a switched system to analyze the global stability of the closed-loop system.The advantage of the method was that the chattering of system output and instability caused by asynchronous switching can be eliminated.The simulation illustrates the effectiveness of the proposed control scheme in comparison with the existing MRAC controller with gain scheduling for turbofan engine.展开更多
随着越来越多的微电网MG(microgrid)接入到电力系统中,其运行控制技术成为提升可再生能源RESs(renewable energy sources)利用率的关键技术之一。然而,MG在并网与孤岛2种运行模式切换时,受RESs出力不确定性以及2种运行模式下电压、频率...随着越来越多的微电网MG(microgrid)接入到电力系统中,其运行控制技术成为提升可再生能源RESs(renewable energy sources)利用率的关键技术之一。然而,MG在并网与孤岛2种运行模式切换时,受RESs出力不确定性以及2种运行模式下电压、频率和相角不一致等因素影响,极易造成模式切换过程中电压和频率波动大等问题。为此,首先提出了一种基于线性二次调节器LQR(linear quadratic regulator)的MG模式平滑切换控制方法,以减小模式切换过程中MG相关参数的剧烈波动。所提方法利用传统LQR方法和状态反馈理论,建立了平滑调节模型;然后,设计了基于二自由度结构的平滑线性二次调节器及其参数选择原则,以最小化模式切换过程中MG相关参数的暂态变化;最后,通过仿真分析与实验验证了所提方法的有效性与优越性。与其他方法相比,所提方法可有效降低MG相关参数约22%的超调百分率,缩短约13%的MG电压与频率振荡时间,同时,所提方法易于实现,且与常见双环PI控制兼容性较好。展开更多
The aircraft engine multi-loop control system is described and the switching control theory is introduced to solve the regulating and protecting control problems in this paper. The aircraft engine multi-loop control s...The aircraft engine multi-loop control system is described and the switching control theory is introduced to solve the regulating and protecting control problems in this paper. The aircraft engine multi-loop control system is firstly described and the control problems are formulated. Secondly, the theory of the smooth switching control is devoted and a new extended scheme for the smooth switching of a switched control system is introduced. Then, for the key technologies of aero-engines switching control, a design algorithm is presented which can determine which candidate controller should be put in feedback with the plant to achieve a desired performance and the procedure to design the aircraft engine multi-loop control system is detailed. The switching performance objectives and the switching scheme are given and a family of PID controllers and compensators is designed. The simulation shows that using the switching control design method can not only improve the dynamic performance of the aircraft engine control system and reduce the switching times, but also guarantee the stability in some peculiar occasions.展开更多
基金supported by National Key Research and Development Technology Project program(SQ2022YFB2400136).
文摘To enable distributed PV to adapt to variations in power grid strength and achieve stable grid connection while enhancing operational flexibility,it is essential to configure grid-connected inverters with an integrated grid-following control mode,allowing smooth switching between GFL and GFM modes.First,impedance models of GFL and GFM PV energy storage VSG systems were established,and grid stability was analyzed.Second,an online impedance identification method based on voltage fluctuation data screening was proposed to enhance the accuracy of impedance identification.Additionally,a PV energy storage GFM/GFL VSG smooth switching method based on current inner loop compensation was introduced to achieve stable grid-connected operation of distributed photovoltaics under changes in strong and weak power grids.Finally,a grid stability analysis was conducted on the multi-machine parallel PV ESS,and a simulation model of a multi-machine parallel PV ESS based on current inner loop compensation was established for testing.Results showed that,compared to using a single GFM or single GFL control for the PV VSG system,the smooth switching method of multi-machine parallel PV ESS effectively suppresses system resonance under variations in power grid strength,enabling adaptive and stable grid-connected operations of distributed PV.
基金supported by the National Natural Science Foundation under Grant 62273189the Shandong Province Natural Science Foundation under Grant ZR2021MF005Systems Science Plus Joint Research Program of Qingdao University under Grant XT2024201 of China supporting this research work.
文摘This article investigates the anti-disturbance and stabilization problems for the nonlinear uncertain permanent magnet synchronous motor(PMSM)with stator voltage saturation and unknown load.A smooth switching mechanism is presented to structure the adaptive integral terminal sliding mode control(SMC)strategy.The control design consists of compensation control and nominal control,which improves the rapidity and accuracy of trajectory tracking.The smooth saturation model based on the error function is applied to approximate the voltage saturation phenomenon.Additionally,to deal with the adverse effects of various unknown disturbances,including model parameter uncertainties and unknown external load disturbances,an improved disturbance observer(DO)is proposed.This observer effectively suppresses the fluctuations caused by fixed gain during the starting period of the system.Finally,the experimental results under different conditions show that the proposed strategy has good tracking and disturbance suppression performances.
基金supported by the National Natural Science Foundation of China(Nos.61273083 and 61374012)
文摘This paper is concerned with a systematic method of smooth switching linear parameter- varying （LPV） controllers design for a morphing aircraft with a variable wing sweep angle. The morphing aircraft is modeled as an LPV system, whose scheduling parameter is the variation rate of the wing sweep angle. By dividing the scheduling parameter set into subsets with overlaps, output feedback controllers which consider smooth switching are designed and the controllers in over- lapped subsets are interpolated from two adjacent subsets. A switching law without constraint on the average dwell time is obtained which makes the conclusion less conservative. Furthermore, a systematic algorithm is developed to improve the efficiency of the controllers design process. The parameter set is divided into the fewest subsets on the premise that the closed-loop system has a desired performance. Simulation results demonstrate the effectiveness of this approach.
基金supported by the Aeronautical Science Foundation of China(20175752045)。
文摘A tilt-rotor aircraft has three flight modes: helicopter mode, airplane mode and conversion mode. Unlike the traditional aircraft, the tilt-rotor aircraft, which combines the characteristics of helicopters and fixed-wing aircraft, is a complex multi-body system with the violent variation of the aerodynamic parameters. For these characteristics, a new smooth switching control scheme is provided for the tilt-rotor aircraft. First, the reference commands for airspeed and nacelle angles are calculated by analyzing the conversion corridor and the conversion path. Subsequently, based on the finite-time switching theorem, an average dwell time condition is designed to guarantee the stability in the switching process. Besides, considering the state vibrations and bumps may appear in switching points, the fuzzy weighted logic is employed to improve the system transient performance. For disturbance rejection, three extended state observers are designed separately to estimate the disturbances in the switched systems. Compared with the traditional auto disturbance rejection control and proportion integration differentiation control, this method overcomes the conservatism of wasting the whole model information. The control performances of robustness and smoothness are verified with simulation, which shows that the new smooth switching control scheme is more targeted and superior than the traditional design method.
文摘A model reference adaptive control(MRAC)with smooth switching scheme was proposed for piecewise linear systems,and the method was utilized in turbofan engine control to avoid the discontinuity of control input.In this scheme,each sub-region of the operating envelope had its own MRAC controller,and smooth indicator function based smooth switching scheme was introduced to switch multiple controllers smoothly at the boundary of adjacent sub-regions.The Lyapunov stability analysis indicated that the proposed smooth switching scheme can guarantee the convergence of the closed-loop system during the controllers switching.The tracking error system was converted into a switched system to analyze the global stability of the closed-loop system.The advantage of the method was that the chattering of system output and instability caused by asynchronous switching can be eliminated.The simulation illustrates the effectiveness of the proposed control scheme in comparison with the existing MRAC controller with gain scheduling for turbofan engine.
文摘随着越来越多的微电网MG(microgrid)接入到电力系统中,其运行控制技术成为提升可再生能源RESs(renewable energy sources)利用率的关键技术之一。然而,MG在并网与孤岛2种运行模式切换时,受RESs出力不确定性以及2种运行模式下电压、频率和相角不一致等因素影响,极易造成模式切换过程中电压和频率波动大等问题。为此,首先提出了一种基于线性二次调节器LQR(linear quadratic regulator)的MG模式平滑切换控制方法,以减小模式切换过程中MG相关参数的剧烈波动。所提方法利用传统LQR方法和状态反馈理论,建立了平滑调节模型;然后,设计了基于二自由度结构的平滑线性二次调节器及其参数选择原则,以最小化模式切换过程中MG相关参数的暂态变化;最后,通过仿真分析与实验验证了所提方法的有效性与优越性。与其他方法相比,所提方法可有效降低MG相关参数约22%的超调百分率,缩短约13%的MG电压与频率振荡时间,同时,所提方法易于实现,且与常见双环PI控制兼容性较好。
基金supported by the National Natural Science Foundation of China (Grant No. 61104146/F030203)Innovation Plan of Aero Engine Complex System Safety by the Ministry of Education Chang Jiang Scholars of China (Grant No. IRT0905)
文摘The aircraft engine multi-loop control system is described and the switching control theory is introduced to solve the regulating and protecting control problems in this paper. The aircraft engine multi-loop control system is firstly described and the control problems are formulated. Secondly, the theory of the smooth switching control is devoted and a new extended scheme for the smooth switching of a switched control system is introduced. Then, for the key technologies of aero-engines switching control, a design algorithm is presented which can determine which candidate controller should be put in feedback with the plant to achieve a desired performance and the procedure to design the aircraft engine multi-loop control system is detailed. The switching performance objectives and the switching scheme are given and a family of PID controllers and compensators is designed. The simulation shows that using the switching control design method can not only improve the dynamic performance of the aircraft engine control system and reduce the switching times, but also guarantee the stability in some peculiar occasions.
