Time filter

Source Type

Kong F.,Xian Jiaotong University | Zhang B.,Xian Jiaotong University | Wang Y.,Xian Jiaotong University | Zhen W.,Sichuan Electric Power Research Institute | Zhang A.,Xuji Group Corporation
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2014

In order to improve the reliability and sensitivity of single-terminal transient-based protection, an ultra-high-speed directional element is proposed for the relay protection of HVDC transmission line, which effectively determines the fault direction according to the difference between the forward traveling wave energy and the backward traveling wave energy when different fault directions exist. A closed-loop test system consisting of RTDS and HVDC control & protection devices is built to test the performance of proposed directional element. Results show that, immune to the fault location and transition resistance and suitable for different voltage levels and different operating modes of HVDC projects, it determines the fault direction accurately and rapidly, which improves the performance of single-terminal transient-based protection effectively. Besides, it can be used to form a pilot directional protection. Source

Yi Y.-P.,University of Shanghai for Science and Technology | Wang W.,University of Shanghai for Science and Technology | Zu L.-F.,Xuji Group Corporation
Guangzi Xuebao/Acta Photonica Sinica | Year: 2015

To reduce the test error, the orthogonal double beam spectrophotometer was designed. The orthogonal double beam spectrophotometer uses one photoelectric conversion system which includes one photodiode, one filtration and amplification, one AD conversion and adds a producer of orthogonal signal which is a rotatable disk and non-opaque somewhere. In each cycle the reference signal and sample signal get through the producer of orthogonal signal and project to the photoelectric conversion system. In this way, the signals collected by the photoelectric conversion system in each cycle are composite and consist of the reference signal, sample signal and dark current signal, each of which will be separated by the master control system of FPGA as each code and restored for the following calculation and analysis. Since the error caused by the differences of photoelectric transducer and collecting time is avoided theoretically, the measurement accuracy of double beam spectrophotometer can be improved through taking one photoelectric conversion system and adding a producer of orthogonal signal. The experimental results show that the orthogonal double beam spectrophotometer has advantages in stability and accuracy. © 2015, Chinese Optical Society. All right reserved. Source

Wu J.,Xian Xu Ji Power Electronic Technology Co. | Liu X.,Xian Xu Ji Power Electronic Technology Co. | Yao W.,Xuji Group Corporation
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2015

A method of optimized control period design is proposed for the converter valve control equipment used in large-scale multi-node HVDC-flexible based on MMC(Modular Multilevel Converter). According to the working principle, control architecture and modulation modes of MMC, three key indicators influencing the control performance of converter valve are proposed: the number of valve output level, the DC voltage fluctuation and the initial surge current during valve unlocking. Their quantitative constraint on the converter valve control period is theoretically analyzed, which is verified by simulations and experiments. The result of optimized design is the maximum valve control period which satisfies three indicators simultaneously. An example of its engineering application is given. ©, 2015, Electric Power Automation Equipment Press. All right reserved. Source

State Grid Corporation of China, Nanjing Southeast University, BEI JING XJ Electrical CO. and Xu Ji Group Corporation | Date: 2013-04-18

The present invention provides an integrated battery dispatching system with centralized charging and centralized allocation, which comprises an initial parameter setting module (

State Grid Corporation of China and Xu Ji Group Corporation | Date: 2012-08-28

The present invention relates to an IEEE1588 protocol negative testing method, comprises steps of: connecting a IEEE1588 tester and a slave clock DUT to establish a real-time closed-loop feedback mechanism; taking the IEEE1588 tester as a master clock, and establishing a stable time synchronization with the slave clock DUT; obtaining the timing offset or path delay of the slave clock DUT before disturbance; assembling an abnormal message in a frame and sending it to the slave clock DUT; calculating the timing offset or path delay increment after disturbance of the abnormal message; determining whether there is a sudden change in the timing offset or path delay of the slave clock DUT, wherein if there is no sudden change, the test passes; otherwise the test fails. This testing method uses the field of correction field (correction Field) in the IEEE1588 message to magnify the response of the slave clock DUT to the abnormal message stimulus, and realizes a real-time closed-loop detection to efficiently verify whether the message processing logic of the slave clock DUT follows the IEEE1588 protocol.

Discover hidden collaborations