Advances in Mechanics Engineering

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Authors: Jun Mei, Bin Liu, Jian Yong Zheng, Lei Yao
Abstract: Considerable attention is given towards developing Superconducting fault current limiter (SFCL) due to increasing short circuit levels in transmission lines, which itself imposes further changes on the measured impendence at the relaying point and causes significant impact on the lines’ relay protection, especially on the distance protection as the single-phase grounding fault occurs. In this paper, resistive superconducting fault current limiter connected to the grid is studied as the model to analysis how SFCL affects the grounded short-circuit impedance relay’s setting, then an new setting method of distance protection for the SFCL-equipped line is proposed. Finally, a power system model is built to analysis the theory by PSCAD / EMTDC simulation software. The results show that in the condition of using the impedance relays’ new setting method, impedance measurement error is greatly reduced, SFCL and line distance protection can work in coordination with each other properly.
Authors: Ping Liu
Abstract: The snow and wind loading model of a bisectional astronomical dome was established. The press of the astronomical dome has been calculated. With the analysis of the loading mode of the dome when it was opening or closing, the maximum power of the electromotor has been calculated. The results are very valuable for calculating the snow and wind loading and designing the maximum power of the electromotor of the bisectional astronomical.
Authors: Song Wang, Guang Da Li
Abstract: A new method named Windowed Least Square (WLS) to test main parameters of Permanent Magnet Synchronous Motor (PMSM) is proposed in this paper. Compared with Extended Kalman Filter (EKF) & Elman neural network and Recursive Least Square (RLS), WLS guarantees identification accuracy and excellent timeliness, and the issue of data saturation of RLS can be avoided. The PMSM model is built combining on-line parameter identification with Active Disturbance Rejection Control (ADRC) to improve the control performance of PMSM. The simulation results demonstrate that the performance of ADRC system using online estimation strategy is better than that of the system using PID method.
Authors: Bing Han, Yan Xia Liu, Fu Yang, Feng Han, Yuan Yuan Liu, Jing Yu Nang
Abstract: This paper mainly focuses on harmonics suppression in power network. Led to by the problem of the fluorescent lamp circuit power factor, the harmonics are recorded by the analysis instrument SR760 about their influence on the circuit current. The method of filtering the harmonics with second-order filter circuit was put forward and then the waveform was simulated after filtration with the simulating software called Pspice, and thereby checks the filtering effects.
Authors: Yu Hua Wang, Peng Yu Wang, Guo Qing Zhang
Abstract: Temperature is an important parameter for the characterization of the transformer and the motor running. Winding temperature test according to the actual operation of the traction transformer and motor temperature protection device requirements, in-depth study, temperature test of the traction transformer based on virtual instrument and traction motor winding resistance method, the method using LabVIEW to develop test software, respectively, for data acquisition, data playback, data analysis and processing, data file management functions, and temperature test equipment, not only real-time test system, but also post-processing the data after the test, in order to analysis of the factors that affect the temperature of the windings. Validity of the method is proved by experiments.
Authors: Jin Zhao Zhang
Abstract: According to two three-phase asynchronous motors system running by connectionless-mode, and considering the system to be required to run in strict synchronous way under different load, the method of field-oriented vector control is used. Thus, the control loops of rotor flux, torque and rotor speed are constructed to make two-motor system run synchronously by torque distribution. The simulation results illustrate its effectiveness and good dynamic and static performance.
Authors: Ying Chen, Liang Hong Li, Zhi Yong Li
Abstract: A kind of self-couple transformer voltage-elevating fly-back circuit topology is presented in this paper, and analyses the operating principle in detail. A voltage-elevating fly-back type DC-DC convertor based on theory is designed. Finally, the feasibility of self-couple transformer voltage-elevating fly-back circuit is testified by experiment.
Authors: Ai Yuan Wang
Abstract: The paper presents some search energy-saving algorithms and the latest research for induction motor. Based on the algorithms, the realization in vector control has been set up. The search time, current fluctuation, and final efficiency have been compared by a simulation case, which found the basis for further engineering application.
Authors: Xue Wu Ji, Hong Liang Tian, Ya Hui Liu, Ning Sun
Abstract: In the design of an electric power steering system (EPS), the smoothness of assistant torque is one of the key performances. In order to reduce the torque ripple caused by the low precision of low-cost angle sensor embodied in the system and to improve the steering comfort, this paper analyzed the influence of low cost angle sensor on the torque ripple of a permanent magnet synchronous motor (PMSM), and optimized the rotor angle signal with speed recursion method and Kalman filtering method. The optimization results of the two methods were compared, and the experiment results showed that Kalman filtering method can optimize the angle signal better.
Authors: Xue Wu Ji, Ning Sun, Ya Hui Liu
Abstract: The dynamic performance of an electric power steering system (EPS) is deteriorated by the inertia of assistant motor embodied in EPS. To compensate the effect of motor inertia and improve the dynamic performance of EPS, the angular acceleration of the motor rotor is needed. However, the angular acceleration cannot be derived by differentiating the rotor angle signal of the permanent magnet synchronous motor (PMSM) directly, for the noise will be amplified. This paper attempts to get motor angular acceleration signal through Kalman filtering method and the angular acceleration signal acquired by this method is calibrated with high precision encoder, furthermore, the signal is verified though simulation and experiment of inertia compensation control. All the calibration results and simulation and experiment results of inertia compensation control show that the angular acceleration acquired through Kalman filtering method is available for the realization of motor inertia compensation control and can achieve the purpose of improving the dynamic performance of the steering system.

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