Advanced Materials Research Vols. 433-440

Abstract: Research on fault diagnosis of condenser has a great significance to safe and efficient operation of power plant. In view of shortcomings of existing diagnosis methods, this paper proposed a fault diagnosis method of condenser based on improved credibility theory，and applied the merits of credibility reasoning to the fault diagnosis of condenser. By proposing a more rational expression way of symptoms and some mathematical equations which can convert field data into symptoms’ credibility, this paper provided a solid basis for acquiring symptoms’ information accurately. Meanwhile, the setting method of rule confidence of credibility rule was improved, which can make the process of credibility reasoning closer to human experts thinking. Experiment results show that this model meets the demand of condenser fault diagnosis well and has important theoretical significance and practical value.

Abstract: The aim of web-based 3D visualization of monitoring over materials haulage to rock-fill dam is to achieve 3D visual expression on internet for transporting vehicles and the surroundings, which is hydropower project construction site layout. On the basis of analysis on 3D visualization process based on 3DS MAX and principles of web-based 3D visualization based on ActiveX technology, the implementation scheme of web-based 3D visualization of monitoring over materials haulage to dam is designed and its implementation methods are analyzed in detail. The real-time motoring and analysis system of materials haulage to rock-fill dam with network, digitalization and visualization, which is developed in B/S architecture, provides supports to engineering construction management.

Abstract: In order to realize high power and reliability of speed control system, fault-tolerant induction motor control system based on three-level inverter is studied in this paper. Based on three-level inverter, a fault-tolerant inverter topology with an extra leg providing the current path during the post-fault operation is proposed. A corresponding control strategy is investigated to avoid voltage drift of the dc link midpoint. In this paper, an induction motor direct slip linear control (DSLC) is employed and investigated to reduce torque ripple and flux magnitude deviation in three-level system. Both simulation and experimental system have been set up to verify the effectiveness of the proposed control strategy.

Abstract: The effective DC power modulation controller influences the security and stability of AC/DC interconnected power system significantly. Based on the direct feedback linearization model of parallel AC/DC transmission system, the DC power modulation controller is designed by using the dynamical adaptive sliding mode control designing method. Using an adaptive technique to estimate the switching control gain and damping coefficient, the dynamical sliding surface is proposed to eliminate tremble. The proposed adaptive sliding mode control scheme can be implemented without the requirement that the bounds of the uncertainties and the disturbances should be known in advance; meanwhile its design is very simple. The simulation results show that this proposed controller is superior to the nonlinear H∞ DC power modulation controller in damping oscillation and robustness.

Abstract: This paper describes the structure and the magnetic circuit of switched reluctance motor with segmental rotors (SSRM), and presents the control strategy of speed closed-loop by regulating the turn-on angle of the main switches in the power converter based on PI algorithm. The turn-off angle is optimized according to different speeds of the motor. The deviation of the rotor speed is the input control parameter of PI controller, and the turn-on angle is the output control parameter. The strategy of current chopping control is used for comparing with angle position control when rotor speed is high. Both the simulation and experimental results show the well transient, steady performance and robustness of SSRM based on the angle position controller.

Abstract: Some modifications of conventional neuron proportional-integral-differential controller (NPID) are presented in this paper to prevent its slow dynamic response and loss of control in case of improper learning factors. The quasi-step signal replaces the step signal as the reference signal to improve the dynamic characteristics. The control output of NPID is modified every step by multiplying a penalty factor called senior teacher signal to suppress further the overshoot and compress the settling time. The steady-state error from the modified NPID (MNPID) is reduced or removed by adjusting dynamically reference input signal while excluding the pseudo steady state. Lots of simulation experiments are done to prove the stability and convergence of the MNPID control algorithm.

Abstract: This paper proposes an obstacle avoidance scheme of a novel mobile robot system for automatic search of books in libraries based on the radio frequency identification (RFID). Nowadays, most of the libraries utilize the barcode identification technique, since it is of low cost. However, our experiments show that using RFID adequately can save more labor and improve the library management efficiency, since RFID has many advantages, i.e., large information storage and long identification distance, etc., whose application in library management information system has great development potential. Based the advantages of its long-distance identification ability combined with the close accurate positioning technologies, an intelligent mobile robot system for automatic search of books anywhere in libraries is design in our project, which can effectively improve the book search efficiency, saves the massive cost and improve the library informatization level. According to this mobile robot, we give a fuzzy multisensor fusion technique based obstacle avoidance method, which can make the intelligent robot searching the desired books automatically in libraries. Both the simulation and the actual experiments validate the obstacle-avoiding algorithm.

Abstract: With the increase of transformer capacity, local overheating caused by leakage magnetic field affects the normal work and safe problems of transformer. How to reduce the additional loss and eliminate local overheating must be paid full attention to the design and manufacturing process of large transformer. In this paper, the leakage magnetic fields of clamps, clips and tank are analyzed. The distribution of leakage magnetic field in various parts of the transformer is obtained. Results of the analysis according with the engineering practice will be helpful for the optimal design of transformer.

Abstract: Decoupling the stator current into magnetizing current and torque current, the vector control technique improves the performance of AC drive system effectively. However, the rotor time constant varies widely with rotor temperature and the flux level of the machine, which decreases the quality of the drive system. By the contrastive analysis of the variable current on-line estimation methods, this paper uses the Model Reference Adaptive System (MRAS) and designs a set of self-adaption estimation arithmetic which has its basis on the Lyapunov theorem of stability. The simulation shows that the estimation arithmetic has the characteristics of fast convergence speed, few stability errors, good track performance and etc. On the basis of simulation of the rotor time constant on-line estimation, this paper designs the system of vector control with the rotor time constant on-line estimation and has the simulation. According to the simulation results, applying the estimation to the vector control system can improve the performance of the system effectively and establish the theoretical basis of the research on the high-performance AC drive system.

Abstract: By describing the relation between business partners in the energy-saving chain of building engineering, this paper revealed the formation and evolution of business partner relationship in the energy-saving chain of building engineering, proposed the selection method of business partner, and made discussion on the game model of cooperation and competition between participants when at least one party was active participant, and then put forward multiple feasible mechanisms to promote the cooperation in energy-saving chain of building, including reward and punishment mechanism, supervision mechanism, reputation mechanism and so on.