基于模块化多电平换流器(Multilevel Modular Converter,MMC)的柔性直流输电系统在电压源换流器高压直流输电(High Voltage Direct Current,HVDC)领域得到了广泛应用.如何处理直流侧故障是MMC所要面对的难题之一.由于混合式大容量高压...基于模块化多电平换流器(Multilevel Modular Converter,MMC)的柔性直流输电系统在电压源换流器高压直流输电(High Voltage Direct Current,HVDC)领域得到了广泛应用.如何处理直流侧故障是MMC所要面对的难题之一.由于混合式大容量高压直流断路器技术的研究尚未成熟,利用换流器自身清除故障电流成为未来柔性直流输电系统清除直流故障的首选策略.在分析已有子模块的基础上,提出一种新型的具备直流故障隔离能力的经济型MMC拓扑.该新型子模块拓扑由两个半桥型子模块串联组成,每个半桥型子模块电容被一分为二,这使得子模块内部附加器件的耐压值得以降低.在换流器闭锁后,无论电流正向或负向流入子模块,子模块内部电容都会提供一个反极性的电容电压将故障电流隔离.在PSCAD/EMTDC平台下搭建单端5电平MMC-HVDC系统及经济性分析结果表明,该新型子模块故障隔离能力良好,其经济性高于现有各类具有直流故障隔离能力子模块拓扑.展开更多
A novel three-module robot has been introduced. It can change its configuration to adapt to the uneven terrain and to improve its tipover stability. This three-module tracked robot has three kinds of symmetry configur...A novel three-module robot has been introduced. It can change its configuration to adapt to the uneven terrain and to improve its tipover stability. This three-module tracked robot has three kinds of symmetry configuration. They are line type, triangle type, and row type. After the factors and the countermeasures of mobile robot＇s tipover problem are analyzed, stability pyramid and tipover stabil-ity index are proposed to globally determinate the mobile robot＇s static stability and dynamic stability. The shape shifting robot is tested by this technique under the combined disturbance of pitch, roll and yaw in simulation. The simulation result shows that this technique is effective for the analysis of mobile robot＇s tipover stability, especially for the reconfigurable or shape shifting modular robot. Experiments on three symmetry configurations are made under unstructured environments. The environment experiment shows the same result as that of the simulation that the triangle type configuration has the best stability. Both simulation and experiment provide a valid reference for the reconfigurable robot＇s potential application.展开更多
Most of the existing screw drive in-pipe robots cannot actively adjust the maximum traction capacity, which limits the adaptability to the wide range of variable environment resistance, especially in curved pipes. In ...Most of the existing screw drive in-pipe robots cannot actively adjust the maximum traction capacity, which limits the adaptability to the wide range of variable environment resistance, especially in curved pipes. In order to solve this problem, a screw drive in-pipe robot based on adaptive linkage mechanism is proposed. The differential property of the adaptive linkage mechanism allows the robot to move without motion interference in the straight and varied curved pipes by adjusting inclining angles of rollers self-adaptively. The maximum traction capacity of the robot can be changed by actively adjusting the inclining angles of rollers. In order to improve the adaptability to the variable resistance, a torque control method based on the fuzzy controller is proposed. For the variable environment resistance, the proposed control method can not only ensure enough traction force, but also limit the output torque in a feasible region. In the simulations, the robot with the proposed control method is compared to the robot with fixed inclining angles of rollers. The results show that the combination of the torque control method and the proposed robot achieves the better adaptability to the variable resistance in the straight and curved pipes.展开更多
文摘基于模块化多电平换流器(Multilevel Modular Converter,MMC)的柔性直流输电系统在电压源换流器高压直流输电(High Voltage Direct Current,HVDC)领域得到了广泛应用.如何处理直流侧故障是MMC所要面对的难题之一.由于混合式大容量高压直流断路器技术的研究尚未成熟,利用换流器自身清除故障电流成为未来柔性直流输电系统清除直流故障的首选策略.在分析已有子模块的基础上,提出一种新型的具备直流故障隔离能力的经济型MMC拓扑.该新型子模块拓扑由两个半桥型子模块串联组成,每个半桥型子模块电容被一分为二,这使得子模块内部附加器件的耐压值得以降低.在换流器闭锁后,无论电流正向或负向流入子模块,子模块内部电容都会提供一个反极性的电容电压将故障电流隔离.在PSCAD/EMTDC平台下搭建单端5电平MMC-HVDC系统及经济性分析结果表明,该新型子模块故障隔离能力良好,其经济性高于现有各类具有直流故障隔离能力子模块拓扑.
基金This project is supported by National Hi-Tech Research and Development Program of China(863 Program, No.2001AA422360) Chinese Academy of Sciences Advanced Manufacturing Technology R&D Base Foundation, Chrna(No.F000112).
文摘A novel three-module robot has been introduced. It can change its configuration to adapt to the uneven terrain and to improve its tipover stability. This three-module tracked robot has three kinds of symmetry configuration. They are line type, triangle type, and row type. After the factors and the countermeasures of mobile robot＇s tipover problem are analyzed, stability pyramid and tipover stabil-ity index are proposed to globally determinate the mobile robot＇s static stability and dynamic stability. The shape shifting robot is tested by this technique under the combined disturbance of pitch, roll and yaw in simulation. The simulation result shows that this technique is effective for the analysis of mobile robot＇s tipover stability, especially for the reconfigurable or shape shifting modular robot. Experiments on three symmetry configurations are made under unstructured environments. The environment experiment shows the same result as that of the simulation that the triangle type configuration has the best stability. Both simulation and experiment provide a valid reference for the reconfigurable robot＇s potential application.
基金Supported by National Natural Science Foundation of China(Grant No.61273345)
文摘Most of the existing screw drive in-pipe robots cannot actively adjust the maximum traction capacity, which limits the adaptability to the wide range of variable environment resistance, especially in curved pipes. In order to solve this problem, a screw drive in-pipe robot based on adaptive linkage mechanism is proposed. The differential property of the adaptive linkage mechanism allows the robot to move without motion interference in the straight and varied curved pipes by adjusting inclining angles of rollers self-adaptively. The maximum traction capacity of the robot can be changed by actively adjusting the inclining angles of rollers. In order to improve the adaptability to the variable resistance, a torque control method based on the fuzzy controller is proposed. For the variable environment resistance, the proposed control method can not only ensure enough traction force, but also limit the output torque in a feasible region. In the simulations, the robot with the proposed control method is compared to the robot with fixed inclining angles of rollers. The results show that the combination of the torque control method and the proposed robot achieves the better adaptability to the variable resistance in the straight and curved pipes.
