Advanced Materials Research Vols. 383-390

Abstract: Ethernet Passive Optical Networks (EPONs) are promising communication technologies for distribution automation system (DAS). However, EPONs have very specific security requirements, due to the broadcast character of the transmission medium. Based on the identity-based cryptography (IBC), and utilizing logical key hierarchy (LKH) approach, this paper presents an efficient key establishment scheme for distribution automation system using EPON. And the analysis results are also given in the paper.

Abstract: The advantages and disadvantages of various power transformer fault detection methods are analyzed. According to the different sonic information of power transformers under different operation conditions, a new method for the power transformer fault detection based on sonic information is introduced. The overall structure of this method and the principle of intelligent maintenance are described. Preliminary operations proved that the method is feasible.

Abstract: Thrust asymmetry is dangerous for aircraft, especially in the phases of approach and landing. This paper proposes a new technology to compensate the thrust asymmetry in lateral of large aircraft. The dynamic characteristics of aircraft with asymmetric thrust are firstly analyzed in the paper. Then, the controllability conditions and balanced flight attitude in the case of thrust asymmetry are studied. Based on the mathematic model of Airbus 300, a thrust asymmetry lateral compensator is designed for the phases of approach and landing to ensure the safety of approach and landing. Numerical simulation results show that the designed compensator (control law) can compensate the asymmetric thrust very well.

Abstract: Designed a device with PLC and inverter for transformer cooling control system. The structure of fuzzy controller is built with PLC. By calculating and testing, fuzzy and fuzzy control rules are established. Practical computing for the PLC to control the output lookup table is given. Using this technique, transformer cooling system energy consumption will be reduced, transformer’s coolers life will be extended and transformer cooling system automation level will be increased.

Abstract: For the characteristics of permanent magnet linear motor (PMLSM) servo system in machine tool feeding system suffering from the effect of parameter variations, load disturbances and so on, the time-varying sliding mode position and speed controller was designed. By designing the time-varying sliding mode line, the line is changing with time t and its slope does not change during the control process. And the error state of the control system always lies on the sliding mode line from the beginning of any initial state. The reaching phase is eliminated. During the design process, because of the control signal is restricted, optimize the controller parameters by minimizing the integral absolute error (IAE). And the convergence rate of error is speeded up. The simulation results prove that the system have global robustness to the parameter variations and disturbance.

Abstract: Moisture content is one of the key controlled variables in grain drying processes. However, this variable cannot or is difficult to be controlled accurately, due to grain drying is a nonlinear process with multi-variables and long delay. To solve this problem, the study is focused on a new intelligent control system for continuous-flow dryer. Based on the manual control idea for controlling the outlet moisture content, a nonlinear process intelligent control algorithm is presented, a human-in-the-loop intelligent control model for grain drying is developed, a system of software structure based on Visual Basic 6.0 is designed.

Abstract: Commutation failures may lead to serious consequences such as DC blocks. A simulation method of joint using the electromagnetic transient program and the electromechanical transient program is presented to analyze commutation failures. This method is realized in two steps. Firstly, the commutation failure critical voltage under a certain operating condition is determined with PSCAD/EMTDC. Secondly, this critical voltage is used in PSS/E, an electromechanical transient program, to analyze commutation failures of AC-DC systems. Using the proposed method, the effect of AC faults on commutation failures of a practical DC link in China is analyzed. Voltage contours is also utilized to improve the visualization of commutation failures. The combined simulation method, which gives consideration to both the simulation accuracy and the simulation efficiency, is beneficial to better analyze commutation failures of large-scale power systems.

Abstract: A novel automated balancing and correcting machine is proposed and studied. Its structure, composition and control system are introduced. A data acquisition card with USB2.0 interface is used to obtain the real-time unbalanced signal. The rotor unbalance and the mass need to be removed are calculated according to the unbalanced measurement principle. The feed which is needed to complete the correction is deduced by integration method on the basis unbalance measurement and correction principle. The AC servo motors with high precision and fast response are used to drive the rotor to achieve fast and accurate unbalance measurement and correction. A prototype according to the principle is manufactured to test the thinking. Experiments proved that the unbalance reducing rate at one time correction more than 95%. It is necessary to further industrial development.

Abstract: The three-phase short-circuit fault of the 500 kV busbar of Waigaoqiao No.2 Power Plant was described, and the fault recorder data was analyzed for short-circuit current. The RMS of short-circuit current decaying fundamental frequency component, DC component and the attenuation time constant was obtained by Fourier transform, extrapolating with the exponential function. Finally, Corresponding suggestions for grid operation and management were also proposed.

Abstract: In this paper, the electromagnetic design of dual stator-winding induction generator with boost converter to raise output voltage under the minimum speed is presented. When the output voltage of power winding is very low and the output current very high, the large winding turns ratio between the control winding and power winding is proposed to reduce the current of control winding. The excited capacitor of power winding and filter inductor of control winding can be canceled. With the boost converter adjusting the out put voltage under the minimum speed, the demand of output voltage of the generator can be achieved. Design results show it is much benefit for reducing the dimension ,cost and weight of the system.