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
To elucidate the principles of notable torque and flux ripple during the steady state of the conventional direct torque control （DTC） of induction machines, the factors of influence torque variation are examined. A ...To elucidate the principles of notable torque and flux ripple during the steady state of the conventional direct torque control （DTC） of induction machines, the factors of influence torque variation are examined. A new torque ripple minimization algorithm is proposed. The novel method eradicated the torque ripple by imposing the required stator voltage vector in each control cycle. The M and T axial components of the stator voltage are accomplished by measuring the stator flux error and the expected incremental value of the torque at every sampling time. The maximum angle rotation allowed is obtained. Experimental results showed that the proposed method combined with the space vector pulse width modulation （SVPWM） could be implemented in most existing digital drive controllers, offering high performance in both steady and transient states of the induction drives at full speed range. The result of the present work implies that torque fluctuation could be eliminated by imposing proper stator voltage, and the proposed scheme could not only maintain constant switching frequency for the inverter, but also solve the heating problem and current harmonics in traditional induction motor drives.展开更多
The paper presents an adaptive controller formulated for a class of nonaffine discrete-time systems with non-strict forms and unknown dynamics.The controller operates based solely on the measured output,thus obviating...The paper presents an adaptive controller formulated for a class of nonaffine discrete-time systems with non-strict forms and unknown dynamics.The controller operates based solely on the measured output,thus obviating the need for knowledge of the physical order of the controlled plant.Utilizing an ideal solution and equivalent dynamics,the approach integrates an adaptive network with feedback and robust controllers to establish a closed-loop system.A learning law is derived under practical conditions of the designed parameters,ensuring effective closed-loop performance based on pure-output feedback.The controller’s effectiveness is validated through both numerical and experimental systems,with results meeting the conditions specified in the main theorem.Comparative analysis highlights the controller’s highly satisfactory performance and its advantages.This research offers a promising approach to adaptive control for discrete-time systems with non-strict dynamics,providing practical solutions for systems with unknown dynamics and indeterminate system order.展开更多
Inhibitory control of movement in motor learning requires the ability to suppress an inappropriate action, a skill needed to stop a planned or ongoing motor response in response to changes in a variety of environments...Inhibitory control of movement in motor learning requires the ability to suppress an inappropriate action, a skill needed to stop a planned or ongoing motor response in response to changes in a variety of environments. This study used a stop-signal task to determine whether transcranial direct-current stimulation over the pre-supplementary motor area alters the reaction time in motor inhibition. Forty healthy subjects were recruited for this study and were randomly assigned to either the transcranial direct-current stimulation condition or a sham-transcranial direct-current stimulation condition. All subjects consecutively performed the stop-signal task before, during, and after the delivery of anodal transcranial direct-current stimulation over the pre-supplementary motor area （pre-transcranial direct-current stimulation phase, transcranial direct-current stimulation phase, and post-transcranial direct-current stimulation phase）. Compared to the sham condition, there were significant reductions in the stop-signal processing times during and after transcranial direct-current stimulation, and change times were significantly greater in the transcranial direct-current stimulation condition. There was no significant change in go processing-times during or after transcranial direct-current stimulation in either condition. Anodal transcranial direct-current stimulation was feasibly coupled to an interactive improvement in inhibitory control. This coupling led to a decrease in the stop-signal process time required for the appropriate responses between motor execution and inhibition. However, there was no transcranial direct-current stimulation effect on the no-signal reaction time during the stop-signal task. Transcranial direct-current stimulation can adjust certain behaviors, and it could be a useful clinical intervention for patients who have difficulties with response inhibition.展开更多
针对柔性直流输电系统(voltage source converter based high voltage direct current transmission,VSC-HVDC)控制参数设计过程中存在的鲁棒性差、依赖已知电路参数、工程设计经验化等问题,提出一种基于马尔科夫转换场(Markov transiti...针对柔性直流输电系统(voltage source converter based high voltage direct current transmission,VSC-HVDC)控制参数设计过程中存在的鲁棒性差、依赖已知电路参数、工程设计经验化等问题,提出一种基于马尔科夫转换场(Markov transition field,MTF)与深度确定性策略梯度算法(deep deterministic policy gradient,DDPG)结合的鲁棒性强、不依赖电路参数特性以及可视化的VSC-HVDC控制参数优化设计方法。首先,采用马尔科夫转换场将电路功率、电压等一维时序波形数据转换为二维马尔科夫转换场域图像并使用马尔科夫转换场损失函数(Markov transition field loss,MTFL)判断二维转换域图的数据波动性;其次,将MTFL损失函数与DDPG算法相结合,综合利用MTFL损失函数对系统输出时序数据动态特性评价能力更强的优点和DDPG算法泛化性能优秀的特点,实现VSC-HVDC系统控制参数优化;最后,通过MATLAB模拟和实验结果验证该方法的有效性。展开更多
在受端交流侧发生故障时,现有依赖耗能装置的基于模块化多电平换流器的多端柔性直流(modular multilevel converter based multi-terminal direct current,MMC-MTDC)输电系统,其盈余功率处理方案存在经济性差和能量浪费等问题。为充分发...在受端交流侧发生故障时,现有依赖耗能装置的基于模块化多电平换流器的多端柔性直流(modular multilevel converter based multi-terminal direct current,MMC-MTDC)输电系统,其盈余功率处理方案存在经济性差和能量浪费等问题。为充分发挥MMC-MTDC系统自有盈余功率消纳能力,减少对耗能装置的依赖,文中提出一种基于主从能量控制的多站极间交互消纳策略。首先,建立相应的MMC-MTDC控制模型,并对其通过能量控制实现盈余功率消纳的可行性进行分析。随后,引入MMC三维度模型,实现换流站各极能量解耦控制,并通过构建的MMC-MTDC系统简化模型,对各类型换流站开展主动能量控制设计。在此基础上,类比主从控制思想,构建适用于不同受端站极交流故障及两类盈余功率情况的主从能量时序控制逻辑,以实现各站极之间的能量裕度协调利用。最后,在PSCAD/EMTDC平台搭建MMC-MTDC系统仿真模型进行实验验证。仿真结果表明,所提控制策略能够在不依赖耗能装置的前提下,有效协调多站极之间的能量控制,适应多种盈余功率故障情况,成功实现故障穿越。展开更多
以水光互补新能源基地经送端双换流站柔性直流输电系统为对象,研究考虑支撑受端频率的水光互补新能源基地与多端柔直(multi-terminal direct current,MTDC)协同控制问题,提出既考虑送端双换流站协同配合,又体现大基地-多端柔直系统功率...以水光互补新能源基地经送端双换流站柔性直流输电系统为对象,研究考虑支撑受端频率的水光互补新能源基地与多端柔直(multi-terminal direct current,MTDC)协同控制问题,提出既考虑送端双换流站协同配合,又体现大基地-多端柔直系统功率传递过程的协同频率支撑控制方法。首先,设计考虑受端频率稳定的水光互补新能源基地-多端柔直协同控制架构;随后,建立考虑大基地-多端柔直频率支撑控制的受端电网频率响应模型,应用前向差分法将其离散化,以便嵌入频率支撑控制参数时域优化模型;接着,提出考虑受端频率稳定需求、大基地-柔直调节能力及小干扰稳定的频率支撑控制参数优化方法;最后,通过PSCAD/EMTDC仿真验证送端双换流站协同控制的必要性及所提频率支撑控制参数优化方法的有效性。展开更多
【目的】采用真双极接线方式的基于模块化多电平换流器的柔性直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)技术是大规模孤岛风电场高效并网与跨区消纳的主流技术方案之一,在我国张北、江苏如东...【目的】采用真双极接线方式的基于模块化多电平换流器的柔性直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)技术是大规模孤岛风电场高效并网与跨区消纳的主流技术方案之一,在我国张北、江苏如东等直流输电工程广泛采用。然而,送端正负极换流器的控制策略面临平衡双极传输功率和为风电场提供稳定电压支撑的双重挑战。为此,提出了基于有功功率-频率上升/无功功率-电压下垂控制的双极换流器构网协调控制策略。【方法】分析了送端双极换流器接收的有功功率-相位-频率的耦合机理,建立了有功功率-频率上升控制策略,阐明了风电波动下双极换流器功率平衡、频率协调及容量受限工况下的自适应调节机理;揭示了送端双极换流器和风电场电压与无功的耦合关系,建立了受容量和有功功率约束的无功功率-电压下垂控制策略,研究了无功波动时交流母线电压的协调稳定机理。【结果】仿真验证表明,在系统功率波动及单极容量受限等多种情况下,所提策略能有效维持双极换流器间的功率动态均衡,并为交流系统提供稳定的电压频率支撑。【结论】所提构网协调控制策略能够有效应对孤岛风电场柔直送出系统送端双极换流器在复杂工况下的功率平衡与电压频率支撑的核心挑战,提升系统的运行稳定性。展开更多
Because brushless direct current(BLDC) motors have the advantages of a compact size, high power density, high efficiency, and long operating life time, they are widely used in many industrial products and electric tra...Because brushless direct current(BLDC) motors have the advantages of a compact size, high power density, high efficiency, and long operating life time, they are widely used in many industrial products and electric traction systems. It is known that the BLDC motors have no brushes for commutation. They are commutated with electronically commutation. So, the rotor position information of the BLDC motors must be known to understand which winding will be energized according to the energizing sequence. In most of the existing BLDC motor drivers, rotor position information is detected by Hall effect sensors. This kind of mechanical position sensors will bring additional connections and costs, reliability decrease and noise increase. In order to improve the control performance and extend the range of speed regulation for BLDC motors, a position sensorless control method is proposed in this paper. In the proposed control method, rotor position information of the BLDC motors is detected from the back electromagnetic forces(back-EMFs) which are estimated by an unknown-input observer with line to line currents and line to line voltages. For the purpose of verifying the effectiveness of the proposed control method, a model is built and simulated on the Matlab/Simulink platform. The simulation results show that the speed regulation performance of BLDC motors is improved compared with using Hall effect sensors. At the same time, the reliability of the BLDC motors is improved and the costs of them are reduced because the position sensor is eliminated.展开更多
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supported by the National Natural Science Foundation of China (Grant No.2004EA105003)
文摘To elucidate the principles of notable torque and flux ripple during the steady state of the conventional direct torque control （DTC） of induction machines, the factors of influence torque variation are examined. A new torque ripple minimization algorithm is proposed. The novel method eradicated the torque ripple by imposing the required stator voltage vector in each control cycle. The M and T axial components of the stator voltage are accomplished by measuring the stator flux error and the expected incremental value of the torque at every sampling time. The maximum angle rotation allowed is obtained. Experimental results showed that the proposed method combined with the space vector pulse width modulation （SVPWM） could be implemented in most existing digital drive controllers, offering high performance in both steady and transient states of the induction drives at full speed range. The result of the present work implies that torque fluctuation could be eliminated by imposing proper stator voltage, and the proposed scheme could not only maintain constant switching frequency for the inverter, but also solve the heating problem and current harmonics in traditional induction motor drives.
文摘The paper presents an adaptive controller formulated for a class of nonaffine discrete-time systems with non-strict forms and unknown dynamics.The controller operates based solely on the measured output,thus obviating the need for knowledge of the physical order of the controlled plant.Utilizing an ideal solution and equivalent dynamics,the approach integrates an adaptive network with feedback and robust controllers to establish a closed-loop system.A learning law is derived under practical conditions of the designed parameters,ensuring effective closed-loop performance based on pure-output feedback.The controller’s effectiveness is validated through both numerical and experimental systems,with results meeting the conditions specified in the main theorem.Comparative analysis highlights the controller’s highly satisfactory performance and its advantages.This research offers a promising approach to adaptive control for discrete-time systems with non-strict dynamics,providing practical solutions for systems with unknown dynamics and indeterminate system order.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology of Korea of Republic, No. 2012R1A1B4003477
文摘Inhibitory control of movement in motor learning requires the ability to suppress an inappropriate action, a skill needed to stop a planned or ongoing motor response in response to changes in a variety of environments. This study used a stop-signal task to determine whether transcranial direct-current stimulation over the pre-supplementary motor area alters the reaction time in motor inhibition. Forty healthy subjects were recruited for this study and were randomly assigned to either the transcranial direct-current stimulation condition or a sham-transcranial direct-current stimulation condition. All subjects consecutively performed the stop-signal task before, during, and after the delivery of anodal transcranial direct-current stimulation over the pre-supplementary motor area （pre-transcranial direct-current stimulation phase, transcranial direct-current stimulation phase, and post-transcranial direct-current stimulation phase）. Compared to the sham condition, there were significant reductions in the stop-signal processing times during and after transcranial direct-current stimulation, and change times were significantly greater in the transcranial direct-current stimulation condition. There was no significant change in go processing-times during or after transcranial direct-current stimulation in either condition. Anodal transcranial direct-current stimulation was feasibly coupled to an interactive improvement in inhibitory control. This coupling led to a decrease in the stop-signal process time required for the appropriate responses between motor execution and inhibition. However, there was no transcranial direct-current stimulation effect on the no-signal reaction time during the stop-signal task. Transcranial direct-current stimulation can adjust certain behaviors, and it could be a useful clinical intervention for patients who have difficulties with response inhibition.
文摘针对柔性直流输电系统(voltage source converter based high voltage direct current transmission,VSC-HVDC)控制参数设计过程中存在的鲁棒性差、依赖已知电路参数、工程设计经验化等问题,提出一种基于马尔科夫转换场(Markov transition field,MTF)与深度确定性策略梯度算法(deep deterministic policy gradient,DDPG)结合的鲁棒性强、不依赖电路参数特性以及可视化的VSC-HVDC控制参数优化设计方法。首先,采用马尔科夫转换场将电路功率、电压等一维时序波形数据转换为二维马尔科夫转换场域图像并使用马尔科夫转换场损失函数(Markov transition field loss,MTFL)判断二维转换域图的数据波动性;其次,将MTFL损失函数与DDPG算法相结合,综合利用MTFL损失函数对系统输出时序数据动态特性评价能力更强的优点和DDPG算法泛化性能优秀的特点,实现VSC-HVDC系统控制参数优化;最后,通过MATLAB模拟和实验结果验证该方法的有效性。
文摘在受端交流侧发生故障时,现有依赖耗能装置的基于模块化多电平换流器的多端柔性直流(modular multilevel converter based multi-terminal direct current,MMC-MTDC)输电系统,其盈余功率处理方案存在经济性差和能量浪费等问题。为充分发挥MMC-MTDC系统自有盈余功率消纳能力,减少对耗能装置的依赖,文中提出一种基于主从能量控制的多站极间交互消纳策略。首先,建立相应的MMC-MTDC控制模型,并对其通过能量控制实现盈余功率消纳的可行性进行分析。随后,引入MMC三维度模型,实现换流站各极能量解耦控制,并通过构建的MMC-MTDC系统简化模型,对各类型换流站开展主动能量控制设计。在此基础上,类比主从控制思想,构建适用于不同受端站极交流故障及两类盈余功率情况的主从能量时序控制逻辑,以实现各站极之间的能量裕度协调利用。最后,在PSCAD/EMTDC平台搭建MMC-MTDC系统仿真模型进行实验验证。仿真结果表明,所提控制策略能够在不依赖耗能装置的前提下,有效协调多站极之间的能量控制,适应多种盈余功率故障情况,成功实现故障穿越。
文摘以水光互补新能源基地经送端双换流站柔性直流输电系统为对象,研究考虑支撑受端频率的水光互补新能源基地与多端柔直(multi-terminal direct current,MTDC)协同控制问题,提出既考虑送端双换流站协同配合,又体现大基地-多端柔直系统功率传递过程的协同频率支撑控制方法。首先,设计考虑受端频率稳定的水光互补新能源基地-多端柔直协同控制架构;随后,建立考虑大基地-多端柔直频率支撑控制的受端电网频率响应模型,应用前向差分法将其离散化,以便嵌入频率支撑控制参数时域优化模型;接着,提出考虑受端频率稳定需求、大基地-柔直调节能力及小干扰稳定的频率支撑控制参数优化方法;最后,通过PSCAD/EMTDC仿真验证送端双换流站协同控制的必要性及所提频率支撑控制参数优化方法的有效性。
文摘【目的】采用真双极接线方式的基于模块化多电平换流器的柔性直流输电(modular multilevel converter based high voltage direct current,MMC-HVDC)技术是大规模孤岛风电场高效并网与跨区消纳的主流技术方案之一,在我国张北、江苏如东等直流输电工程广泛采用。然而,送端正负极换流器的控制策略面临平衡双极传输功率和为风电场提供稳定电压支撑的双重挑战。为此,提出了基于有功功率-频率上升/无功功率-电压下垂控制的双极换流器构网协调控制策略。【方法】分析了送端双极换流器接收的有功功率-相位-频率的耦合机理,建立了有功功率-频率上升控制策略,阐明了风电波动下双极换流器功率平衡、频率协调及容量受限工况下的自适应调节机理;揭示了送端双极换流器和风电场电压与无功的耦合关系,建立了受容量和有功功率约束的无功功率-电压下垂控制策略,研究了无功波动时交流母线电压的协调稳定机理。【结果】仿真验证表明,在系统功率波动及单极容量受限等多种情况下,所提策略能有效维持双极换流器间的功率动态均衡,并为交流系统提供稳定的电压频率支撑。【结论】所提构网协调控制策略能够有效应对孤岛风电场柔直送出系统送端双极换流器在复杂工况下的功率平衡与电压频率支撑的核心挑战,提升系统的运行稳定性。
文摘Because brushless direct current(BLDC) motors have the advantages of a compact size, high power density, high efficiency, and long operating life time, they are widely used in many industrial products and electric traction systems. It is known that the BLDC motors have no brushes for commutation. They are commutated with electronically commutation. So, the rotor position information of the BLDC motors must be known to understand which winding will be energized according to the energizing sequence. In most of the existing BLDC motor drivers, rotor position information is detected by Hall effect sensors. This kind of mechanical position sensors will bring additional connections and costs, reliability decrease and noise increase. In order to improve the control performance and extend the range of speed regulation for BLDC motors, a position sensorless control method is proposed in this paper. In the proposed control method, rotor position information of the BLDC motors is detected from the back electromagnetic forces(back-EMFs) which are estimated by an unknown-input observer with line to line currents and line to line voltages. For the purpose of verifying the effectiveness of the proposed control method, a model is built and simulated on the Matlab/Simulink platform. The simulation results show that the speed regulation performance of BLDC motors is improved compared with using Hall effect sensors. At the same time, the reliability of the BLDC motors is improved and the costs of them are reduced because the position sensor is eliminated.
