The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow ...The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.展开更多
Finite-control-set model predictive control(FCSMPC)has advantages of multi-objective optimization and easy implementation.To reduce the computational burden and switching frequency,this article proposed a simplified M...Finite-control-set model predictive control(FCSMPC)has advantages of multi-objective optimization and easy implementation.To reduce the computational burden and switching frequency,this article proposed a simplified MPC for dual three-phase permanent magnet synchronous motor(DTPPMSM).The novelty of this method is the decomposition of prediction function and the switching optimization algorithm.Based on the decomposition of prediction function,the current increment vector is obtained,which is employed to select the optimal voltage vector and calculate the duty cycle.Then,the computation burden can be reduced and the current tracking performance can be maintained.Additionally,the switching optimization algorithm was proposed to optimize the voltage vector action sequence,which results in lower switching frequency.Hence,this control strategy can not only reduce the computation burden and switching frequency,but also maintain the steady-state and dynamic performance.The simulation and experimental results are presented to verify the feasibility of the proposed strategy.展开更多
An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse o...An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.展开更多
Circulating currents in a microgrid increase the power loss of the microgrid, reduce the operational efficiency, as well as affect the power quality of the microgrid. The existing literature is seldom concerned with m...Circulating currents in a microgrid increase the power loss of the microgrid, reduce the operational efficiency, as well as affect the power quality of the microgrid. The existing literature is seldom concerned with methods to suppress the loop currents using fuzzy logic control. In this paper, a method based on fuzzy control of droop coefficients is proposed to suppress the circulating currents inside the microgrid.The method combines fuzzy control with droop control and can achieve the effect of suppressing the circulating currents by adaptively adjusting the droop coefficients to make the power distribution between each subgrid more balanced. To verify the proposed method, simulation is carried out in Matlab/Simulink environment, and the simulation results show that the proposed method is significantly better than the traditional proportional-integral control method. The circulating currents reduce from about 10 A to several nanoamperes, the bus voltage and frequency drops are significantly improved, and the total harmonic distortion rate of the output voltage reduces from 4.66% to 1.06%. In addition, the method used in this paper can be extended to be applied in multiple inverters connected in parallel, and the simulation results show that the method has a good effect on the suppression of circulating currents among multiple inverters.展开更多
The merits of compressed air energy storage(CAES)include large power generation capacity,long service life,and environmental safety.When a CAES plant is switched to the grid-connected mode and participates in grid reg...The merits of compressed air energy storage(CAES)include large power generation capacity,long service life,and environmental safety.When a CAES plant is switched to the grid-connected mode and participates in grid regulation,using the traditional control mode with low accuracy can result in excess grid-connected impulse current and junction voltage.This occurs because the CAES output voltage does not match the frequency,amplitude,and phase of the power grid voltage.Therefore,an adaptive linear active disturbance-rejection control(A-LADRC)strategy was proposed.Based on the LADRC strategy,which is more accurate than the traditional proportional integral controller,the proposed controller is enhanced to allow adaptive adjustment of bandwidth parameters,resulting in improved accuracy and response speed.The problem of large impulse current when CAES is switched to the grid-connected mode is addressed,and the frequency fluctuation is reduced.Finally,the effectiveness of the proposed strategy in reducing the impact of CAES on the grid connection was verified using a hardware-in-the-loop simulation platform.The influence of the k value in the adaptive-adjustment formula on the A-LADRC was analyzed through simulation.The anti-interference performance of the control was verified by increasing and decreasing the load during the presynchronization process.展开更多
Wire-arc directed energy deposition(wire-arc DED)enables the fabrication of large-scale metal components with rapid manufacturing ability and diverse material selection,making it a compelling technology in industries ...Wire-arc directed energy deposition(wire-arc DED)enables the fabrication of large-scale metal components with rapid manufacturing ability and diverse material selection,making it a compelling technology in industries and defenses.However,challenges in both macroscale and microscale defects still limit printed component widespread applications.Recent advances in automatic and intelligent technologies have brought a range of quality controllable strategies to the forefront.This review covers these new strategies for the printing component,including path planning,process monitoring,auxiliary processes,and post processing,while discussing the expectation for structure and quality improvement.In addition,the work brings new areas of intelligent wire-arc DED development,including advances in digital twin,visualization,and human-processing interaction to promote its performance.It is anticipated that a focus on intelligent system will be key to smart and high-quality manufacturing for future wire-arc DED.展开更多
Aiming at the challenge of complex load balancing coordination for a three-phase four-leg(3P4L)based multi-ended low voltage flexible DC distribution system(M-LVDC)considering unbalanced power compensation,this paper ...Aiming at the challenge of complex load balancing coordination for a three-phase four-leg(3P4L)based multi-ended low voltage flexible DC distribution system(M-LVDC)considering unbalanced power compensation,this paper proposes a phase-split power decoupling unbalanced compensation strategy based load balancing strategy for 3P4L based M-LVDC.Firstly,the topology and operation principle of the 3P4L-based M-LVDC system is introduced,and quasi-proportional resonant(QPR)based phase-split power current control for the 3P4L converter is proposed.Secondly,a load-balancing control strategy considering unbalanced compensation for 3P4L-based MLVDC is presented,in which the control diagrams for each 3P4L-based converter are detailed.The core idea of the proposed strategy is to comprehensively consider the imbalance compensation and load rate balancing between the two areas to calculate the split-phase power and current reference values of each 3P4L converter and achieve the static error-free tracking of the reference values through the QPR current inner-loop control.These reference values are then tracked with zero steady-state error using QPR current inner-loop control.Finally,the effectiveness of the proposed control strategy is verified through a 3P4L M-LVDC case study conducted on the PSCAD/EMTDC software.Theresults indicate that the proposed method not only can reduce the three-phase imbalance degrees from>20% to<0.5%,but also achieve excellent balanced load rates,with the load-rate difference smaller than 1.5%.展开更多
In quadrupeds,the cervical and lumbar circuits work together to achieve the speed-dependent gait expression.While most studies have focused on how local lumbar circuits regulate limb coordination and gaits,relatively ...In quadrupeds,the cervical and lumbar circuits work together to achieve the speed-dependent gait expression.While most studies have focused on how local lumbar circuits regulate limb coordination and gaits,relatively few studies are known about cervical circuits and even less about locomotor gaits.We use the previously published models by Danner et al.(DANNER,S.M.,SHEVTSOVA,N.A.,FRIGON,A.,and RYBAK,I.A.Computational modeling of spinal circuits controlling limb coordination and gaits in quadrupeds.e Life,6,e31050(2017))as a basis,and modify it by proposing an asymmetric organization of cervical and lumbar circuits.First,the model reproduces the typical speed-dependent gait expression in mice and more biologically appropriate locomotor parameters,including the gallop gait,locomotor frequencies,and limb coordination of the forelimbs.Then,the model replicates the locomotor features regulated by the M-current.The walk frequency increases with the M-current without affecting the interlimb coordination or gaits.Furthermore,the model reveals the interaction mechanism between the brainstem drive and ionic currents in regulating quadrupedal locomotion.Finally,the model demonstrates the dynamical properties of locomotor gaits.Trot and bound are identified as attractor gaits,walk as a semi-attractor gait,and gallop as a transitional gait,with predictable transitions between these gaits.The model suggests that cervical-lumbar circuits are asymmetrically recruited during quadrupedal locomotion,thereby providing new insights into the neural control of speed-dependent gait expression.展开更多
The boost converter feeding a constant power load (CPL) is a non-minimum phase system that is prone to the destabilizing effects of the negative incremental resistance of the CPL and presents a major challenge in the ...The boost converter feeding a constant power load (CPL) is a non-minimum phase system that is prone to the destabilizing effects of the negative incremental resistance of the CPL and presents a major challenge in the design of stabilizing controllers. A PWM-based current-sensorless robust sliding mode controller is developed that requires only the measurement of the output voltage. An extended state observer is developed to estimate a lumped uncertainty signal that comprises the uncertain load power and the input voltage, the converter parasitics, the component uncertainties and the estimation of the derivative of the output voltage needed in the implementation of the controller. A linear sliding surface is used to derive the controller, which is simple in its design and yet exhibits excellent features in terms of robustness to external disturbances, parameter uncertainties, and parasitics despite the absence of the inductor’s current feedback. The robustness of the controller is validated by computer simulations.展开更多
A highly efficient and re liable topology-dual buck half bridge inverter (DBI) is introduced. The existenc e of discontinuous conduction mode (DCM) operation state requires the bias of in du ctor current for DBI imple...A highly efficient and re liable topology-dual buck half bridge inverter (DBI) is introduced. The existenc e of discontinuous conduction mode (DCM) operation state requires the bias of in du ctor current for DBI implemented with linear controllers like ramp comparison SP WM (RCSPWM) controllers. A novel operation scheme for DBI and a hysteresis curre nt controlled dual buck half bridge inverter (HCDBI) are proposed. The bias curr ent required by RCSPWM DBI is eliminated and conduction losses are dramatically reduced. HCDBI has greatly improved the modulation performance in DCM region for the benefit of its excellent command tracking capability. The operational schem e and control strategy are presented. Power losses of the conventional half brid ge inverter (CHBI) and HCDBI are compared with mathematical computation, and exp erimental verification is also executed. Both calculational and experimental res ults verify that HCDBI has a superior switching performance over CHBI. Its exce llent high frequency operational capacity provides another access to realize high fre quency operation of inverters.展开更多
In view of the current sensors failure in electric pitch system,a variable universe fuzzy fault tolerant control method of electric pitch control system based on single current detection is proposed.When there is sing...In view of the current sensors failure in electric pitch system,a variable universe fuzzy fault tolerant control method of electric pitch control system based on single current detection is proposed.When there is single or two-current sensor fault occurs,based on the proposed method the missing current information can be reconstructed by using direct current（DC）bus current sensor and the three-phase current can be updated in time within any two adjacent sampling periods,so as to ensure stability of the closed-loop system.And then the switchover and fault tolerant control of fault current sensor would be accomplished by fault diagnosis method based on adaptive threshold judgment.For the reconstructed signal error caused by the modulation method and the main control target of electric pitch system,a variable universe fuzzy control method is used in the speed loop,which can improve the anti-disturbance ability to load variation,and the robustness of fault tolerance system.The results show that the fault tolerant control method makes the variable pitch control system still has ideal control characteristics in case of sensor failure although part of the system performance is lost,thus the correctness of the proposed method is verified.展开更多
An all-digital hybrid current regulation scheme for the single-phase shunt active power filter （APF） is presented. The proposed hybrid current control scheme integrates the deadbeat control and the dual-mode structu...An all-digital hybrid current regulation scheme for the single-phase shunt active power filter （APF） is presented. The proposed hybrid current control scheme integrates the deadbeat control and the dual-mode structure repetitive control （DMRC） so that it can offer superior steady-state performance and good transient features. Unlike the conventional schemes, the proposed scheme-based APF can compensate both the odd and the even order harmonics in grid. The detailed design criteria and the stability analysis of the proposed hybrid current controller are presented. Moreover, an improved structure which incorporates the proposed hybrid controller and the resonant controller for tracking specific order harmonics is given. The relationships between the resonant controller and different repetitive control schemes are discussed. Experimental results verify the effectiveness and advantages of the proposed hybrid control scheme.展开更多
There are two kinds of unbalance vibrations—force vibration and displacement vibration due to the existence of unbalance excitation in active magnetic bearings（AMB） system. And two unbalance compensation methods—c...There are two kinds of unbalance vibrations—force vibration and displacement vibration due to the existence of unbalance excitation in active magnetic bearings（AMB） system. And two unbalance compensation methods—closed-loop feedback and open loop feed-forward are presented to reduce the force vibration. The transfer function order of the control system directly influencing the system stability will be increased when the closed-loop method is adopted, which makes the real-time compensation not easily achieved. While the open loop method would not increase the primary transfer function order, it provides conditions for real-time compensation. But the real-time compensation signals are not easy to be obtained in the open loop method. To implement real-time force compensation, a new method is proposed to reduce the force vibration caused by the rotor unbalance on the basis of AMB active control. The method realizes real-time and on-line force auto-compensation based on H∞ controller and one novel feed-forward compensation controller, which makes the rotor rotate around its inertia axis. The time-variable feed-forward compensatory signal is provided by a modified adaptive variable step-size least mean square（VSLMS） algorithm. And the relevant least mean square（LMS） algorithm parameters are used to solve the H∞ controller weighting functions. The simulation of the new method to compensate some frequency-variable and sinusoidal signals is completed by MATLAB programming, and real-time compensation is implemented in the actual AMB experimental system. The simulation and experiment results show that the compensation scheme can improve the robust stability and the anti-interference ability of the whole AMB system by using H∞ controller to achieve close-loop control, and then real-time force unbalance compensation is implemented. The proposed research provides a new control strategy containing real-time algorithm and H∞ controller for the force compensation of AMB system. And the stability of the control system is finally improved.展开更多
In the conventional cascade control structure of aerospace electrically powered actuators, the current（or electromagnetic torque） loop plays a critical role in realizing a rapid response for a digitally controlled B...In the conventional cascade control structure of aerospace electrically powered actuators, the current（or electromagnetic torque） loop plays a critical role in realizing a rapid response for a digitally controlled Brush Less Direct Current（BLDC） motor. Hysteresis Current Control（HCC） is an effective method in improving the performance of current control for a BLDC motor.Nevertheless, the varying modulating frequency in the traditional HCC causes severe problems on the safety of power devices and the electromagnetic compatibility design. A triangular carrier-based fixed-frequency HCC strategy is expanded by relaxing the constraints on the rising and descending rates of the winding current to advance the capability of HCC to realize fixed-frequency modulation in the steady state. Based on that, a new flexible-bound-size quasi-fixed-frequency HCC is proposed, and the range feasible to realize fixed-frequency modulation control can cover the entire running process in the steady state. Meanwhile, a corresponding digital control strategy is designed,and four digitalization rules are proposed to extend the capacity to achieve fixed-frequency modulation control to the unsteady working state, that is, a novel fixed-frequency modulation is realized.Simulation and experimental results prove the effectiveness of this improved fixed-frequency HCC strategy.展开更多
A feedback control system is needed to restrain plasma vertical displacement in EAST （Experimental Advanced Superconducting Toknmak）. A fast control power supply excites active feedback coils, which produces a magne...A feedback control system is needed to restrain plasma vertical displacement in EAST （Experimental Advanced Superconducting Toknmak）. A fast control power supply excites active feedback coils, which produces a magnetic field to control the plasma＇s displacement. With the development of EAST, new demands on the new fast control power supply have led to an enhanced ability of fast response and output current, as well as a new control mode. The structure of cascaded and paralleled H-bridges can meet the demand of extended capacity, and digital control can reMize current and voltage mixed control mode. The validity of the proposed scheme is confirmed by experiments.展开更多
Aim at improving the stability of the Short-circuiting Gas Metal Arc Welding （GMAW-S） process for the enhanced speed usage, effects of current waveform parameters during short-term on the welding stability have been...Aim at improving the stability of the Short-circuiting Gas Metal Arc Welding （GMAW-S） process for the enhanced speed usage, effects of current waveform parameters during short-term on the welding stability have been investigated by experimental method. The welding power source used for the research is an inverter with a special current waveform control. It is shown that the spatter decreases at first then increases with each increase of the low current period, current increase rate and the maximum current limit. The test results are provided for welding of 1 mm and 3 mm mild steel at speed of 1.2 m/min. The stable GMA W-S process under high speed welding condition has been achieved by optimizing the parameters.展开更多
Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used t...Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents.However,CCVSI with traditional controllers have a limited transient and steady state performance.In this paper,we propose an adaptive dynamic programming(ADP) controller with online learning capability to improve transient response and harmonics.The proposed controller works alongside existing proportional integral(PI) controllers to efficiently track the reference currents in the d-q domain.It can generate adaptive control actions to compensate the PI controller.The proposed system was simulated under different nonlinear(three-phase full wave rectifier) load conditions.The performance of the proposed approach was compared with the traditional approach.We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison.The online learning based ADP controller not only reduced average total harmonic distortion by 18.41%,but also outperformed traditional PI controllers during transients.展开更多
Rectangular wave current control of the electrochemical reduction of nitrobenzene im-proves the selectivity for p-aminophenol(PAP) compared to direct current(d.c.) control at thesame average current density in a flow-...Rectangular wave current control of the electrochemical reduction of nitrobenzene im-proves the selectivity for p-aminophenol(PAP) compared to direct current(d.c.) control at thesame average current density in a flow-by packed-bed reactor.Optimal increase in PAP selectivitycan be obtained at about a frequency of 50Hz and a duty cycle of 0.2.A mathematical model isset up to incorporate the effects of mass transfer,hydrogen evolution and double layer charging,and is solved using the Duhamel’s superposition principle and the modified Crank-Nicolson methodwith the upwind scheme.The conventional d.c.control cases are also calculated for comparison.Calculations can be applied to predict the reaction results under periodic current and d.c.control,but both display the same trends compared to experimental data.展开更多
An energy-based controller of electric current is synthesized for the libration stabilization of an electrodynamic tether system,which consists of a relatively large main-satellite and a sub-satellite of much smaller ...An energy-based controller of electric current is synthesized for the libration stabilization of an electrodynamic tether system,which consists of a relatively large main-satellite and a sub-satellite of much smaller size.Two dynamic models with different levels of accuracy are considered in this work.First,a dumbbell model of the system is used for the controller design,which aims at damping injection on the libration motions via the real-time regulation of the electric current.Furthermore,the efficacy and performance of the proposed scheme are numerically verified by using a more complex multi-body model which accounts for not only the tether flexibility but also the attitude of the main-satellite.展开更多
Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunn...Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunnel length was only a function of the turn-on interval of DC. The potential of Al foil broke at on-off controlling DC by the result from anode polarization curves and potential-time （E-t） responding curves. When DC was switched on, the potential increased abruptly over pitting potential, leading to nucleation of pits at the surface and the growth of tunnels at special length. When DC was switched off, the potential decreased rapidly to a passive value, leading to stoppage of nucleation and death of tunnels. By this way, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Hence, etching of Al foil at this current is beneficial for maintaining a good mechanical strength.展开更多
基金supported in part by Natural Science Foundation of Jiangsu Province under Grant BK20230255Natural Science Foundation of Shandong Province under Grant ZR2023QE281.
文摘The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.
基金supported by the National Natural Science Foundation of China under Grant 5227705。
文摘Finite-control-set model predictive control(FCSMPC)has advantages of multi-objective optimization and easy implementation.To reduce the computational burden and switching frequency,this article proposed a simplified MPC for dual three-phase permanent magnet synchronous motor(DTPPMSM).The novelty of this method is the decomposition of prediction function and the switching optimization algorithm.Based on the decomposition of prediction function,the current increment vector is obtained,which is employed to select the optimal voltage vector and calculate the duty cycle.Then,the computation burden can be reduced and the current tracking performance can be maintained.Additionally,the switching optimization algorithm was proposed to optimize the voltage vector action sequence,which results in lower switching frequency.Hence,this control strategy can not only reduce the computation burden and switching frequency,but also maintain the steady-state and dynamic performance.The simulation and experimental results are presented to verify the feasibility of the proposed strategy.
基金National Natural Science Foundation of China(No.62303107)Fundamental Research Funds for the Central Universities,China(Nos.2232022G-09 and 2232021D-38)Shanghai Sailing Program,China(No.21YF1400100)。
文摘An alternating current(AC)microgrid is a system that integrates renewable power,power converters,controllers and loads.Hierarchical control can manage the frequency of the microgrid to prevent imbalance and collapse of the system.The existing frequency control methods use traditional proportion integration(PI)controllers,which cannot adjust PI parameters in real-time to respond to the status changes of the system.Hierarchical control driven by fuzzy logic allows real-time adjustment of the PI parameters and the method used a two-layer control structure.The primary control used droop control to adjust power distribution,and fuzzy logic was used in the voltage loop of the primary control.The secondary control was added to make up for frequency deviation caused by droop control,and fuzzy logic was used in the secondary frequency control to deal with the dynamic change of frequency caused by the disturbances of loads.The proposed method was simulated in Matlab/Simulink.In the primary control,the proposed method reduced the total harmonic distortion(THD)of two cycles of the output voltage from 4.19%to 3.89%;in the secondary control,the proposed method reduced the frequency fluctuation of the system by about 0.03 Hz and 0.04 Hz when the load was increased and decreased,respectively.The results show that the proposed methods have a better effect on frequency maintenance and voltage control of the AC microgrid.
基金Foundation items:National Natural Science Foundation of China(No.62303107)Fundamental Research Funds for the Central Universities,China(Nos.2232022G-09 and 2232021D-38)Shanghai Sailing Program,China(No.21YF1400100)。
文摘Circulating currents in a microgrid increase the power loss of the microgrid, reduce the operational efficiency, as well as affect the power quality of the microgrid. The existing literature is seldom concerned with methods to suppress the loop currents using fuzzy logic control. In this paper, a method based on fuzzy control of droop coefficients is proposed to suppress the circulating currents inside the microgrid.The method combines fuzzy control with droop control and can achieve the effect of suppressing the circulating currents by adaptively adjusting the droop coefficients to make the power distribution between each subgrid more balanced. To verify the proposed method, simulation is carried out in Matlab/Simulink environment, and the simulation results show that the proposed method is significantly better than the traditional proportional-integral control method. The circulating currents reduce from about 10 A to several nanoamperes, the bus voltage and frequency drops are significantly improved, and the total harmonic distortion rate of the output voltage reduces from 4.66% to 1.06%. In addition, the method used in this paper can be extended to be applied in multiple inverters connected in parallel, and the simulation results show that the method has a good effect on the suppression of circulating currents among multiple inverters.
基金supported by National Natural Science Foundation of China(Project No.52077079).
文摘The merits of compressed air energy storage(CAES)include large power generation capacity,long service life,and environmental safety.When a CAES plant is switched to the grid-connected mode and participates in grid regulation,using the traditional control mode with low accuracy can result in excess grid-connected impulse current and junction voltage.This occurs because the CAES output voltage does not match the frequency,amplitude,and phase of the power grid voltage.Therefore,an adaptive linear active disturbance-rejection control(A-LADRC)strategy was proposed.Based on the LADRC strategy,which is more accurate than the traditional proportional integral controller,the proposed controller is enhanced to allow adaptive adjustment of bandwidth parameters,resulting in improved accuracy and response speed.The problem of large impulse current when CAES is switched to the grid-connected mode is addressed,and the frequency fluctuation is reduced.Finally,the effectiveness of the proposed strategy in reducing the impact of CAES on the grid connection was verified using a hardware-in-the-loop simulation platform.The influence of the k value in the adaptive-adjustment formula on the A-LADRC was analyzed through simulation.The anti-interference performance of the control was verified by increasing and decreasing the load during the presynchronization process.
基金fully appreciate financial support from NingXia Natural Science Foundation for Outstanding Young Scholar(No.2024AAC04002)CAS“Light of West China”Program,National Natural Science Foundation of China(Key Program,No.12232013)Natural Science Foundation of Ningxia(Key Program,No.2022AAC2003)。
文摘Wire-arc directed energy deposition(wire-arc DED)enables the fabrication of large-scale metal components with rapid manufacturing ability and diverse material selection,making it a compelling technology in industries and defenses.However,challenges in both macroscale and microscale defects still limit printed component widespread applications.Recent advances in automatic and intelligent technologies have brought a range of quality controllable strategies to the forefront.This review covers these new strategies for the printing component,including path planning,process monitoring,auxiliary processes,and post processing,while discussing the expectation for structure and quality improvement.In addition,the work brings new areas of intelligent wire-arc DED development,including advances in digital twin,visualization,and human-processing interaction to promote its performance.It is anticipated that a focus on intelligent system will be key to smart and high-quality manufacturing for future wire-arc DED.
基金supported by the key technology project of China Southern Power Grid Corporation(GZKJXM20220041)partly by theNational Key Research and Development Plan(2022YFE0205300).
文摘Aiming at the challenge of complex load balancing coordination for a three-phase four-leg(3P4L)based multi-ended low voltage flexible DC distribution system(M-LVDC)considering unbalanced power compensation,this paper proposes a phase-split power decoupling unbalanced compensation strategy based load balancing strategy for 3P4L based M-LVDC.Firstly,the topology and operation principle of the 3P4L-based M-LVDC system is introduced,and quasi-proportional resonant(QPR)based phase-split power current control for the 3P4L converter is proposed.Secondly,a load-balancing control strategy considering unbalanced compensation for 3P4L-based MLVDC is presented,in which the control diagrams for each 3P4L-based converter are detailed.The core idea of the proposed strategy is to comprehensively consider the imbalance compensation and load rate balancing between the two areas to calculate the split-phase power and current reference values of each 3P4L converter and achieve the static error-free tracking of the reference values through the QPR current inner-loop control.These reference values are then tracked with zero steady-state error using QPR current inner-loop control.Finally,the effectiveness of the proposed control strategy is verified through a 3P4L M-LVDC case study conducted on the PSCAD/EMTDC software.Theresults indicate that the proposed method not only can reduce the three-phase imbalance degrees from>20% to<0.5%,but also achieve excellent balanced load rates,with the load-rate difference smaller than 1.5%.
基金Project supported by the National Natural Science Foundation of China(Nos.12272092 and 12332004)。
文摘In quadrupeds,the cervical and lumbar circuits work together to achieve the speed-dependent gait expression.While most studies have focused on how local lumbar circuits regulate limb coordination and gaits,relatively few studies are known about cervical circuits and even less about locomotor gaits.We use the previously published models by Danner et al.(DANNER,S.M.,SHEVTSOVA,N.A.,FRIGON,A.,and RYBAK,I.A.Computational modeling of spinal circuits controlling limb coordination and gaits in quadrupeds.e Life,6,e31050(2017))as a basis,and modify it by proposing an asymmetric organization of cervical and lumbar circuits.First,the model reproduces the typical speed-dependent gait expression in mice and more biologically appropriate locomotor parameters,including the gallop gait,locomotor frequencies,and limb coordination of the forelimbs.Then,the model replicates the locomotor features regulated by the M-current.The walk frequency increases with the M-current without affecting the interlimb coordination or gaits.Furthermore,the model reveals the interaction mechanism between the brainstem drive and ionic currents in regulating quadrupedal locomotion.Finally,the model demonstrates the dynamical properties of locomotor gaits.Trot and bound are identified as attractor gaits,walk as a semi-attractor gait,and gallop as a transitional gait,with predictable transitions between these gaits.The model suggests that cervical-lumbar circuits are asymmetrically recruited during quadrupedal locomotion,thereby providing new insights into the neural control of speed-dependent gait expression.
文摘The boost converter feeding a constant power load (CPL) is a non-minimum phase system that is prone to the destabilizing effects of the negative incremental resistance of the CPL and presents a major challenge in the design of stabilizing controllers. A PWM-based current-sensorless robust sliding mode controller is developed that requires only the measurement of the output voltage. An extended state observer is developed to estimate a lumped uncertainty signal that comprises the uncertain load power and the input voltage, the converter parasitics, the component uncertainties and the estimation of the derivative of the output voltage needed in the implementation of the controller. A linear sliding surface is used to derive the controller, which is simple in its design and yet exhibits excellent features in terms of robustness to external disturbances, parameter uncertainties, and parasitics despite the absence of the inductor’s current feedback. The robustness of the controller is validated by computer simulations.
文摘A highly efficient and re liable topology-dual buck half bridge inverter (DBI) is introduced. The existenc e of discontinuous conduction mode (DCM) operation state requires the bias of in du ctor current for DBI implemented with linear controllers like ramp comparison SP WM (RCSPWM) controllers. A novel operation scheme for DBI and a hysteresis curre nt controlled dual buck half bridge inverter (HCDBI) are proposed. The bias curr ent required by RCSPWM DBI is eliminated and conduction losses are dramatically reduced. HCDBI has greatly improved the modulation performance in DCM region for the benefit of its excellent command tracking capability. The operational schem e and control strategy are presented. Power losses of the conventional half brid ge inverter (CHBI) and HCDBI are compared with mathematical computation, and exp erimental verification is also executed. Both calculational and experimental res ults verify that HCDBI has a superior switching performance over CHBI. Its exce llent high frequency operational capacity provides another access to realize high fre quency operation of inverters.
基金Natural Science Foundation of Gansu Province(Joint)Project(No.213244)Natural Science Foundation of Gansu Province(No.145RJZA136)Youth Science Foundation of Lanzhou Jiaotong University(No.2013040)
文摘In view of the current sensors failure in electric pitch system,a variable universe fuzzy fault tolerant control method of electric pitch control system based on single current detection is proposed.When there is single or two-current sensor fault occurs,based on the proposed method the missing current information can be reconstructed by using direct current（DC）bus current sensor and the three-phase current can be updated in time within any two adjacent sampling periods,so as to ensure stability of the closed-loop system.And then the switchover and fault tolerant control of fault current sensor would be accomplished by fault diagnosis method based on adaptive threshold judgment.For the reconstructed signal error caused by the modulation method and the main control target of electric pitch system,a variable universe fuzzy control method is used in the speed loop,which can improve the anti-disturbance ability to load variation,and the robustness of fault tolerance system.The results show that the fault tolerant control method makes the variable pitch control system still has ideal control characteristics in case of sensor failure although part of the system performance is lost,thus the correctness of the proposed method is verified.
基金The National Basic Research Program of China(973 Program)(No.2013CB035603)the National Natural Science Foundation of China(No.51007008,51137001)+1 种基金the Ph.D.Programs Foundation of Ministry of Education of China(No.20100092120043)the Fundamental Research Funds for the Central Universities
文摘An all-digital hybrid current regulation scheme for the single-phase shunt active power filter （APF） is presented. The proposed hybrid current control scheme integrates the deadbeat control and the dual-mode structure repetitive control （DMRC） so that it can offer superior steady-state performance and good transient features. Unlike the conventional schemes, the proposed scheme-based APF can compensate both the odd and the even order harmonics in grid. The detailed design criteria and the stability analysis of the proposed hybrid current controller are presented. Moreover, an improved structure which incorporates the proposed hybrid controller and the resonant controller for tracking specific order harmonics is given. The relationships between the resonant controller and different repetitive control schemes are discussed. Experimental results verify the effectiveness and advantages of the proposed hybrid control scheme.
基金supported by National Natural Science Foundation of China(Grant No.50437010)National Hi-tech Research and Development Program of China(863Program,Grant No.2006AA05Z205)Project of Six Talented Peak of Jiangsu Province,China(Grant No.07-D-013)
文摘There are two kinds of unbalance vibrations—force vibration and displacement vibration due to the existence of unbalance excitation in active magnetic bearings（AMB） system. And two unbalance compensation methods—closed-loop feedback and open loop feed-forward are presented to reduce the force vibration. The transfer function order of the control system directly influencing the system stability will be increased when the closed-loop method is adopted, which makes the real-time compensation not easily achieved. While the open loop method would not increase the primary transfer function order, it provides conditions for real-time compensation. But the real-time compensation signals are not easy to be obtained in the open loop method. To implement real-time force compensation, a new method is proposed to reduce the force vibration caused by the rotor unbalance on the basis of AMB active control. The method realizes real-time and on-line force auto-compensation based on H∞ controller and one novel feed-forward compensation controller, which makes the rotor rotate around its inertia axis. The time-variable feed-forward compensatory signal is provided by a modified adaptive variable step-size least mean square（VSLMS） algorithm. And the relevant least mean square（LMS） algorithm parameters are used to solve the H∞ controller weighting functions. The simulation of the new method to compensate some frequency-variable and sinusoidal signals is completed by MATLAB programming, and real-time compensation is implemented in the actual AMB experimental system. The simulation and experiment results show that the compensation scheme can improve the robust stability and the anti-interference ability of the whole AMB system by using H∞ controller to achieve close-loop control, and then real-time force unbalance compensation is implemented. The proposed research provides a new control strategy containing real-time algorithm and H∞ controller for the force compensation of AMB system. And the stability of the control system is finally improved.
基金supported by the National Natural Science Foundation of China (Nos.51275021,61327807)
文摘In the conventional cascade control structure of aerospace electrically powered actuators, the current（or electromagnetic torque） loop plays a critical role in realizing a rapid response for a digitally controlled Brush Less Direct Current（BLDC） motor. Hysteresis Current Control（HCC） is an effective method in improving the performance of current control for a BLDC motor.Nevertheless, the varying modulating frequency in the traditional HCC causes severe problems on the safety of power devices and the electromagnetic compatibility design. A triangular carrier-based fixed-frequency HCC strategy is expanded by relaxing the constraints on the rising and descending rates of the winding current to advance the capability of HCC to realize fixed-frequency modulation in the steady state. Based on that, a new flexible-bound-size quasi-fixed-frequency HCC is proposed, and the range feasible to realize fixed-frequency modulation control can cover the entire running process in the steady state. Meanwhile, a corresponding digital control strategy is designed,and four digitalization rules are proposed to extend the capacity to achieve fixed-frequency modulation control to the unsteady working state, that is, a novel fixed-frequency modulation is realized.Simulation and experimental results prove the effectiveness of this improved fixed-frequency HCC strategy.
基金supported by ITER Program of China(973 Program)(No.2011GB109002)National Natural Science Foundation of China(No.11275056)Hefei University of Technology Doctor Research Foundation of China(No.2011HGBZ1292)
文摘A feedback control system is needed to restrain plasma vertical displacement in EAST （Experimental Advanced Superconducting Toknmak）. A fast control power supply excites active feedback coils, which produces a magnetic field to control the plasma＇s displacement. With the development of EAST, new demands on the new fast control power supply have led to an enhanced ability of fast response and output current, as well as a new control mode. The structure of cascaded and paralleled H-bridges can meet the demand of extended capacity, and digital control can reMize current and voltage mixed control mode. The validity of the proposed scheme is confirmed by experiments.
文摘Aim at improving the stability of the Short-circuiting Gas Metal Arc Welding （GMAW-S） process for the enhanced speed usage, effects of current waveform parameters during short-term on the welding stability have been investigated by experimental method. The welding power source used for the research is an inverter with a special current waveform control. It is shown that the spatter decreases at first then increases with each increase of the low current period, current increase rate and the maximum current limit. The test results are provided for welding of 1 mm and 3 mm mild steel at speed of 1.2 m/min. The stable GMA W-S process under high speed welding condition has been achieved by optimizing the parameters.
文摘Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents.However,CCVSI with traditional controllers have a limited transient and steady state performance.In this paper,we propose an adaptive dynamic programming(ADP) controller with online learning capability to improve transient response and harmonics.The proposed controller works alongside existing proportional integral(PI) controllers to efficiently track the reference currents in the d-q domain.It can generate adaptive control actions to compensate the PI controller.The proposed system was simulated under different nonlinear(three-phase full wave rectifier) load conditions.The performance of the proposed approach was compared with the traditional approach.We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison.The online learning based ADP controller not only reduced average total harmonic distortion by 18.41%,but also outperformed traditional PI controllers during transients.
基金Supported by the State Key Laboratory of Chemical Engineering,National Nature Science Foundation of China,and China Petrochemical Corporation.
文摘Rectangular wave current control of the electrochemical reduction of nitrobenzene im-proves the selectivity for p-aminophenol(PAP) compared to direct current(d.c.) control at thesame average current density in a flow-by packed-bed reactor.Optimal increase in PAP selectivitycan be obtained at about a frequency of 50Hz and a duty cycle of 0.2.A mathematical model isset up to incorporate the effects of mass transfer,hydrogen evolution and double layer charging,and is solved using the Duhamel’s superposition principle and the modified Crank-Nicolson methodwith the upwind scheme.The conventional d.c.control cases are also calculated for comparison.Calculations can be applied to predict the reaction results under periodic current and d.c.control,but both display the same trends compared to experimental data.
基金Supported by the National Natural Science Foundation of China(11002068)the Foundation for the Author of National Excellent Doctoral Dissertation of China(201233)
文摘An energy-based controller of electric current is synthesized for the libration stabilization of an electrodynamic tether system,which consists of a relatively large main-satellite and a sub-satellite of much smaller size.Two dynamic models with different levels of accuracy are considered in this work.First,a dumbbell model of the system is used for the controller design,which aims at damping injection on the libration motions via the real-time regulation of the electric current.Furthermore,the efficacy and performance of the proposed scheme are numerically verified by using a more complex multi-body model which accounts for not only the tether flexibility but also the attitude of the main-satellite.
基金This study was financially supported by Beijing Education Commission,China.
文摘Growth and passivation of tunnels within Al foil by on-off controlling DC etching in 6 wt.% HCI solution has been investigated. It was found that, in a given etchant solution at a special temperature, the longest tunnel length was only a function of the turn-on interval of DC. The potential of Al foil broke at on-off controlling DC by the result from anode polarization curves and potential-time （E-t） responding curves. When DC was switched on, the potential increased abruptly over pitting potential, leading to nucleation of pits at the surface and the growth of tunnels at special length. When DC was switched off, the potential decreased rapidly to a passive value, leading to stoppage of nucleation and death of tunnels. By this way, the longest tunnel length can be controlled and a non-piercing layer can be obtained. Hence, etching of Al foil at this current is beneficial for maintaining a good mechanical strength.
