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
Microwave-assisted ignition(MAI)is a promising technology to improve the ignition stability in internal combustion engines under lean conditions.To investigate the interplay between the microwave pulses and the electr...Microwave-assisted ignition(MAI)is a promising technology to improve the ignition stability in internal combustion engines under lean conditions.To investigate the interplay between the microwave pulses and the electrical characteristics of ignition plasma,the high-time-resolved electrical characteristics of MAI are measured based on the discharge voltage and current profiles with microwave power varying from 0 to 1000 W.The effects of microwave pulse on the electrical characteristics in the breakdown and glow discharge phases are discussed respectively.The results show that the microwave-induced-voltage-decline(MIVD)occurs during the glow discharge phase,which originates from the increment of free electrons and the additional microwave field.However,this voltage decline is insignificant in the breakdown phase.Moreover,as the free electron number reaches a critical value,a shining plasma can be observed between the gap of electrodes and the voltage decline is stabilized to a"saturated voltage curve".Ultimately,the effect of microwave plasma on the enhancement of ignition kernel area is explored.The result indicates that the enhancement effect increases with plasma duration rising.Those enhancements of earlier-generated plasmas are more significant than those of subsequent plasmas due to the distance limit of the plasma propulsive effect.展开更多
When a renewable energy station(RES)connects to the rectifier station(RS)of a modular multilevel converterbased high-voltage direct current(MMC-HVDC)system,the voltage at the point of common coupling(PCC)is determined...When a renewable energy station(RES)connects to the rectifier station(RS)of a modular multilevel converterbased high-voltage direct current(MMC-HVDC)system,the voltage at the point of common coupling(PCC)is determined by RS control methods.For example,RS control may become saturated under fault,and causes the RS to change from an equivalent voltage source to an equivalent current source,making fault analysis more complicated.In addition,the grid code of the fault ride-through(FRT)requires the RES to output current according to its terminal voltage.This changes the fault point voltage and leads to RES voltage regulation and current redistribution,resulting in fault response interactions.To address these issues,this study describes how an MMC-integrated system has five operation modes and three common characteristics under the duration of the fault.The study also reveals several instances of RS performance degradation such as AC voltage loop saturation,and shows that RS power reversal can be significantly improved.An enhanced AC FRT control method is proposed to achieve controllable PCC voltage and continuous power transmission by actively reducing the PCC voltage amplitude.The robustness of the method is theoretically proven under parameter variation and operation mode switching.Finally,the feasibility of the proposed method is verified through MATLAB/Simulink results.展开更多
Accurate,high bandwidth current control is a requirement for high performance vector controlled AC drives.Synchronous PI current regulators are the preferred solution for this purpose.Design and operation principles o...Accurate,high bandwidth current control is a requirement for high performance vector controlled AC drives.Synchronous PI current regulators are the preferred solution for this purpose.Design and operation principles of synchronous PI current regulators are well established.However,there are a number of issues that must be considered,especially when the drive must operate at high synchronous frequencies,including regulator design,effects due to discretization and the associated delays,voltage constraints and current sampling issues among other.Inadmissible degradation of the current regulator performance and consequently of the drive can occur otherwise.展开更多
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.
文摘Microwave-assisted ignition(MAI)is a promising technology to improve the ignition stability in internal combustion engines under lean conditions.To investigate the interplay between the microwave pulses and the electrical characteristics of ignition plasma,the high-time-resolved electrical characteristics of MAI are measured based on the discharge voltage and current profiles with microwave power varying from 0 to 1000 W.The effects of microwave pulse on the electrical characteristics in the breakdown and glow discharge phases are discussed respectively.The results show that the microwave-induced-voltage-decline(MIVD)occurs during the glow discharge phase,which originates from the increment of free electrons and the additional microwave field.However,this voltage decline is insignificant in the breakdown phase.Moreover,as the free electron number reaches a critical value,a shining plasma can be observed between the gap of electrodes and the voltage decline is stabilized to a"saturated voltage curve".Ultimately,the effect of microwave plasma on the enhancement of ignition kernel area is explored.The result indicates that the enhancement effect increases with plasma duration rising.Those enhancements of earlier-generated plasmas are more significant than those of subsequent plasmas due to the distance limit of the plasma propulsive effect.
基金supported in part by the National Key Research and Development Program of China(No.2020YFF0305800)State Grid Science Technology Project(No.520201210025)。
文摘When a renewable energy station(RES)connects to the rectifier station(RS)of a modular multilevel converterbased high-voltage direct current(MMC-HVDC)system,the voltage at the point of common coupling(PCC)is determined by RS control methods.For example,RS control may become saturated under fault,and causes the RS to change from an equivalent voltage source to an equivalent current source,making fault analysis more complicated.In addition,the grid code of the fault ride-through(FRT)requires the RES to output current according to its terminal voltage.This changes the fault point voltage and leads to RES voltage regulation and current redistribution,resulting in fault response interactions.To address these issues,this study describes how an MMC-integrated system has five operation modes and three common characteristics under the duration of the fault.The study also reveals several instances of RS performance degradation such as AC voltage loop saturation,and shows that RS power reversal can be significantly improved.An enhanced AC FRT control method is proposed to achieve controllable PCC voltage and continuous power transmission by actively reducing the PCC voltage amplitude.The robustness of the method is theoretically proven under parameter variation and operation mode switching.Finally,the feasibility of the proposed method is verified through MATLAB/Simulink results.
文摘Accurate,high bandwidth current control is a requirement for high performance vector controlled AC drives.Synchronous PI current regulators are the preferred solution for this purpose.Design and operation principles of synchronous PI current regulators are well established.However,there are a number of issues that must be considered,especially when the drive must operate at high synchronous frequencies,including regulator design,effects due to discretization and the associated delays,voltage constraints and current sampling issues among other.Inadmissible degradation of the current regulator performance and consequently of the drive can occur otherwise.
