Applied Mechanics and Materials Vols. 373-375

Abstract: With the development of our country electric power enterprise, closed-loop pour load operation has become increasingly frequent in power distribution network, the resulting circulation problems affect the safe operation of power grid. The calculation method of system is used by BX type solution fast decomposition method and it is very suitable for distribution integration, by the method we can calculate the steady state current and transient current of closed-loop. It also provide accurate current analysis and control. With analysis of examples, finally indicates that the method can offer good for dispatch staff for closed-loop operation decision support, and it has a certain guiding significance.

Abstract: It studies the changing regulation of fast out-of-step separation criterion based on equivalent two-machine power system. Analysis of the characteristics of the caring variables of fast out-of-step separation criterion on sending end and receiving end is mentioned. In order to solve the problem that the out-of-step connecting line cannot be identified correctly apply on the criterion of the existing fast out-of-step separation if the measurement point at the receiving end, it improves the power angle and active power criterion. The simulation is carried out in our actual grid model with using BPA and the results of the simulation handled by MATLAB proves that the out-of-step of line can be distinguished by using the improved fast out-of-step separation criterion in each end of line.

Abstract: Brushless DC motors, which are applied to the human skeleton boosters, require frequent switch of four-quadrant operation states of forward rotation, backward rotation, electro motion and braking control. This switch generally requires to be soft and smooth without overshoot, big impulse or speed mutation. The general performance of the brushless DC motor control system cant meet this requirement. The main purpose of this paper is to solve this problem by adopting bipolar PWM control which makes it possible to realize the motor operating in four-quadrant and improve its characteristics. In addition, the paper proved the correct and efficiency of this method by using simulation .

Abstract: Transient faults are the dominated kind of threats to operation safety in networked control systems (NCSs), and the runtime detection of them is difficult but a key point in fault tolerance design. In this paper, a novel transient fault detection approach is proposed based on multiple system models. System models are established to show how system works in teleological, functional, behavioral, and structural viewpoints, and operational constraints of the models are set up to capture the runtime violation in which the faults are indicated. A case is presented to investigate the using processes of the proposal and the results show that the transient faults are detected efficiently online.

Abstract: A lateral flight reduced-order controller for a flexible aircraft is presented. It is based on the reduced-order model of the flexible aircraft and the μ-analysis and synthesis toolbox. The first step deals with the order reduction of the full-model by using the balanced-truncation model reduction method. Then the reduced-order H controller is achieved by using the μ-analysis and synthesis theory and applied to the reduced-order model and full-order model of the flexible aircraft. Finally, numerical results are presented and discussed. The simulation results show the efficiency of the reduced-order controller based on the reduced-order model since the close-loop system of the full-order model meets a set of realistic specifications in the frequency and time domains.

Abstract: An operation betweenness based method to assess overloaded lines is proposed. Based on electrical network theory, firstly the branch current sharing factors are deduced; then the operation betweenness of transmission line is defined; finally, on this basis the overload vulnerability of transmission line is assessed. In the proposed method, the impacts of both topological structure and operation modes of power network on vulnerability are considered for the assessment. The physical meaning of the proposed method is determinate and conforms to actual condition of power system, and this method avoids the defect in the complicated network model that the power flows only flow along the shortest path. The correctness of the proposed assessment method is verified by simulation results of IEEE 39-bus system.

Abstract: Intelligent control system of greenhouse based on a technical architecture, which combined with the GPRS/GSM wireless communication module and PLC. The system uses the microcomputer to collect information, GPRS/GSM to communication, PLC to control and other technologies. It realizes the comprehensive environmental dynamic optimization balance control of greenhouse group, temperature, light, water, fertilizer and other environmental factors as the control object. The system saves the cost of production and reduces the pollution of farmland, to achieve high yield, high quality, generate significant economic and ecological benefits. The system improves the level of agricultural production management informationization, automation, modernization of Zhejiang, and have low operation cost, synchronously promotes the agricultural synergism, farmer's income and rural development. Keywords: GPRS/GSM; PLC; facility agriculture, intelligent control, benefit analysis.

Abstract: According to the characteristics of pulse-load torque of the treadmill, the key technical problems of drive control system in the treadmill with a permanent magnet synchronous motor (PMSM for short) are analyzed. The internal disturbance and external disturbance in the system are observed using the extended state observe (ESO for short) and the system is compensated using the auto-disturbance rejection controller (ADRC for short). The simulation results show that ADRC has better dynamic performance and better robustness to the load disturbance and the motor parameter variation.

Abstract: As the scale of modern smart grid gets larger and larger, fast analysis and calculation of power grid is an important research topic now. Starting with analyzing and comparing the traditional power system block methods, a partition strategy is proposed which contains buffer subsystem in each partition. Mutual impedance element in the node impedance matrix could describe the strength of electrical contact between nodes. The buffer subsystem is obtained which has a greater impact on the internal network setting calculation based on electrical contact. Further more, the general rules of buffer subsystem which is suitable for setting calculation have been put forward. At last, it can widely improve the adaptability of setting calculation block computing.

Abstract: This paper splices power grids detailed model of all dispatching areas to form the whole power grids detailed model through power grid model splicing technology based on common information model (CIM). This paper introduces the solution to managing the equivalent model, partitioning the splicing boundary, disposing the device on the border etc. Specific to setting calculation based on the whole power grid, some splicing solutions are also proposed concerning calculation rate and problems demanding large internal storage.