风电变流器(wind power converter,WPC)是风电转换系统的关键部件,承担着风机功率变换和并网的重要功能。WPC故障会造成整个风电机组停运,其可靠性高低对风电转换系统乃至整个风电场的可靠性都有较大影响。由于海上风电场运行环境恶劣,...风电变流器(wind power converter,WPC)是风电转换系统的关键部件,承担着风机功率变换和并网的重要功能。WPC故障会造成整个风电机组停运,其可靠性高低对风电转换系统乃至整个风电场的可靠性都有较大影响。由于海上风电场运行环境恶劣,故障元件的维修与更换困难,WPC对海上风电场整体可靠性的影响也更为严重。基于WPC的故障机理,建立了计及WPC故障的海上风电场风电转换系统可靠性模型。基于该模型,进一步考虑风机尾流效应和风电场集电系统的故障,对海上风电场进行了可靠性评估,研究了WPC故障对海上风电场整体可靠性的影响,并对影响变流器和海上风电场可靠性的主要因素进行了灵敏度分析。算例结果表明,风电机组变流器故障对海上风电场整体可靠性的影响较大,在计及变流器故障的影响后,海上风电场的容量因子将显著降低。展开更多
A new kind of inertial piezoelectric actuator for a micro in-pipe robot is proposed and studied. The actuator is composed of a body, corresponding to a mass rod, and four elastic legs. Each leg is a composite piezoele...A new kind of inertial piezoelectric actuator for a micro in-pipe robot is proposed and studied. The actuator is composed of a body, corresponding to a mass rod, and four elastic legs. Each leg is a composite piezoelectric bimorph beam, made up of a middle metal element, an upper and lower piezoelectric elements. The mechanism is driven by an asymmetric waveform voltage, such as saw-toothed waveform, and utilizes the dynamic relationship between the maximum static friction force and the inertial force. To study the actuator, firstly, the constituent equation of a composite piezoelectric bimorph under both applied voltage and external force was inferred by thermodynamics. Secondly, the dvnamic model of the actuator was established analyzing the relationship between the locomotive states, viz. displacement and velocity, and design parameters, such as piezoelectric strain constant, elastic modulus,length, width and thickness of the piezoelectric element, actuator mass, and driving vohage. At last, the dynamic equation was solved and the theoretical calculation of the inherent frequency was more consistent with the experimental data, which proved the rationality of the model. All these lay a theoretical foundation of the micro actuator parameter optimization and more research on a micro robot.展开更多
文摘风电变流器(wind power converter,WPC)是风电转换系统的关键部件,承担着风机功率变换和并网的重要功能。WPC故障会造成整个风电机组停运,其可靠性高低对风电转换系统乃至整个风电场的可靠性都有较大影响。由于海上风电场运行环境恶劣,故障元件的维修与更换困难,WPC对海上风电场整体可靠性的影响也更为严重。基于WPC的故障机理,建立了计及WPC故障的海上风电场风电转换系统可靠性模型。基于该模型,进一步考虑风机尾流效应和风电场集电系统的故障,对海上风电场进行了可靠性评估,研究了WPC故障对海上风电场整体可靠性的影响,并对影响变流器和海上风电场可靠性的主要因素进行了灵敏度分析。算例结果表明,风电机组变流器故障对海上风电场整体可靠性的影响较大,在计及变流器故障的影响后,海上风电场的容量因子将显著降低。
基金Sponsored by the National Natural Science Foundation of China(Grant No.69774020)the National Doctoral Foundation of China(Grant No.98014106).
文摘A new kind of inertial piezoelectric actuator for a micro in-pipe robot is proposed and studied. The actuator is composed of a body, corresponding to a mass rod, and four elastic legs. Each leg is a composite piezoelectric bimorph beam, made up of a middle metal element, an upper and lower piezoelectric elements. The mechanism is driven by an asymmetric waveform voltage, such as saw-toothed waveform, and utilizes the dynamic relationship between the maximum static friction force and the inertial force. To study the actuator, firstly, the constituent equation of a composite piezoelectric bimorph under both applied voltage and external force was inferred by thermodynamics. Secondly, the dvnamic model of the actuator was established analyzing the relationship between the locomotive states, viz. displacement and velocity, and design parameters, such as piezoelectric strain constant, elastic modulus,length, width and thickness of the piezoelectric element, actuator mass, and driving vohage. At last, the dynamic equation was solved and the theoretical calculation of the inherent frequency was more consistent with the experimental data, which proved the rationality of the model. All these lay a theoretical foundation of the micro actuator parameter optimization and more research on a micro robot.
