Applied Mechanics and Materials Vols. 494-495

Abstract: Considering the influence of the environment for the search-rescue robot to perform tasks, design scheme of the acquisition module for vision navigation system was determined. In the design, FPGA ping-pong operation method was used. The EP4CE15 main control chip module was completed with module method, and the software design of the system was completed, including Quartus II image acquisition project navigator and Nios II system configuration. Finally, the simulation of data transfer was carried on. Simulation results show that the embedded real-time image acquisition is stable.

Abstract: The torque ripple is the important restriction affecting the promotion and application of switched reluctance motor, the analytic expressions to calculate switched reluctance motors tangential force and radial force are derived in this paper, based on analyzing the cause of switched reluctance motor vibration and torque ripple. By improving the stator poles structure, the torque near the commutation points is compensated, which smooth the wave of air gap magnetic field to reduce torque ripple when the stators and the rotors salient poles coincide. In this paper, three structures that puts wedge angle on both sides of the stator poles is presented, and analysis of torque ripple is made. Studies shows that the right size of wedge angle can effectively inhibit the switched reluctance motor torque fluctuations.

Abstract: In order to achieve sensorless control for permanent magnet linear synchronous motor (PMLSM) direct drive system, speed and position of the motor must be estimated. A new high speed sliding mode observer (SMO) is proposed for a PMLSM based on the sliding mode variable structure theory. A Sigmoid function is used for the SMO as a switching function of the control law, eliminating sliding mode chattering and improving its response rate. Simulation results show that the proposed SMO based on Sigmoid function is capable of estimating speed and position of the motor accurately and rapidly, and the proposed PMLSM sensorless control system has a good dynamic response.

Abstract: This paper analyses the harmonic distribution of current and voltage of inverter output based on RSVPWM control strategy and compares the result with normal SVPWM strategy. It gives the random strategy and verifiesthe strategys feasibility. Experimental results show that RSVPWM control method makes harmonic energy evenly distributed in wide frequency band, and changes the original discrete harmonic spectrum into a continuous spectrum on the whole frequency band as much as possible. Random switching frequency SVPWM control scheme could reduce the harmonic energy which focuses on the integral multiple of switching frequency, thus reducing electromagnetic noise and mechanical vibration.

Abstract: This paper study a fault feature extraction method based on wavelet packet transform, using this method to extract fault information of output signal in the NPC three-level inverter fault. After analysis the structure principle of NPC three-level inverter and the wavelet packets fault feature extraction algorithm, brings up a fault feature extraction procedure of NPC three-level inverter based on wavelet packet transform. Through MATLAB simulation experiments, prove the rationality of wavelet packet transform in fault feature extraction, and the reliability in intelligent fault diagnosis.

Abstract: This paper focuses on the current tracking control of three-phase four-wire active power filter (APF). The conventional PI control method usually causes a large deviation of the harmonic compensational current, and results in a slow response, which means that harmonic compensational performance under the conventional PI control is not ideal. In order to improve the compensation performance and the dynamic response speed of APF, the authors present a new control strategy by integrating the parameters online tuning of fuzzy adaptive with the recursive integral PI control algorithm. New algorithm takes full advantages of the characteristic of integrating the deviation of each sample-point of the recursive integral PI control and the adaptive merits of the parameters online tuning algorithm. The simulation experiments indicate that the control algorithm is feasible and can effectively improve the harmonic compensation performance of active power filter.

Abstract: Due to excitation inrush current, no-load transformer accesses system can cause different degree of voltage sag. Therefore presents a method to estimate voltage sag caused by closing no-load transformer. Firstly, accord to the point of saturation magnetic flux and transformer core general single value curve equation to establish general nonlinear magnetization curve. Use the linear features of saturated magnetization curve segment to estimate the maximum inrush current and calculate the maximum depth of voltage sag. According to the magnetic flux decay time to estimate the duration of voltage sag. Simulate closing no-load transformer in a 10kV distribution network, and compare the simulated result with the calculated result. The results show that the proposed method is validity and accuracy.

Abstract: This paper describes the development of a novel high voltage (HV) switch for use in the damping oscillating voltage testing system. Specialized for up to 10 kV rated XLPE partial discharge test application, the switch consists of ten identical IGBT function units in series connection and has a maximum voltage of 20 kV. To solve the synchronization problem of the gate signal, we used the optical fiber to trigger the units. A multiple isolation power-supply system is used for the drive circuit. The operation of proposed switch is tested on an equivalent specimen, confirming the feasibility of this kind of application.

Abstract: This paper presents the development of the Damped AC (DAC) voltage generator for the detection of partial discharge (PD) in distribution power cables. High voltage semiconductor switch (HVSS) and air-core inductor are the key units in the DAC test system. Series connection of insulated gate bipolar transistors (IGBTs) was used to achieve the 20kV HVSS. Based on the Neumanns formula, the inductance of the air-core inductor was investigated. Finally, the performance of the developed DAC system was tested on a 8.7/15 kV cross-linked polyethylene (XLPE) cable in the laboratory, where artificial defect of missing stress tube is made in the cable termination.

Abstract: The principle of detection of partial discharge in MV Metal-Clad Switchgears utilizing Transient Earth Voltage (TEV) method is introduced and some problems in application of the traditional PD detection systems are summarized and analyzed. After that, an improved PD detection system is proposed and established with an advanced technique. The technique involves use of energy method to determine time difference among multiple signals and external trigger method to realize phase integrity during data acquisition process. Laboratory experiment and site tests are conducted and it is proved that the improved detection system is of great effectiveness in PD location and interference identification.