Applied Mechanics and Materials Vols. 385-386

Abstract: A nonlinear adaptive controller is proposed for the design of pulse width modulation voltage-source rectifier with disturbance signals of harmonics to achieve reference velocity tracking. The procedure of the robust controller design is developed via improved backstepping method. With the proposed controller, PWM voltage-source rectifiers can guarantee accuracy of output voltage tracking. Global asymptotic stability of the closed-loop system has been proved. The simulation results demonstrate effectiveness of the presented method.

Abstract: Because of the complex structure, poor working conditions and lots of fault modes of aeroengine , it is necessary to monitor the operational status, accurate localization of aeroengine fault and identify fault to improve the safety and reliability of aircraft. Based on consistency fusion, this paper uses probabilistic neural network to monitor health condition of aeroengine and puts forward a combined method of health condition monitoring based on the consistency fusion and the neural network. The results of test show that this method can quickly monitor the health condition of the aeroengine and has certain reference value for other mechanical equipments condition monitoring.

Abstract: The equivalent salt deposit density (ESDD) of insulator in power system is the main basis of defining pollution classes and mapping pollution areas. However, The meteorological factors on it is complex, using traditional methods is difficult to establish accurate mathematical model to express the relationship, In this paper, the gray theory and neural network model to reflect the changing trend of data series on the apparent effect, Gray neural network model used to predict the insulators ESDD under certain meteorological factors, and to design a neural network compensator correction on the predicted results. The simulation results show that the model has higher prediction accuracy, better than a simple gray neural network model, and have certain theoretical value and practical application value.

Abstract: The power system is facing line losses, low voltage level and some other issues, this article begin with the point of the reactive power optimization, and through with the improved PSO algorithm, we find a way to reduce the line network loss.

Abstract: Smart grid puts forward higher requirements for measurement equipments, so optical current transducer (OCT) used in power system possess broad application prospects. In this paper, magnetism gathering technology is applied in the design of OCTs optical structure and the magnetism gathering optical structure based on solenoid coil is proposed. Compared with traditional bulk optical structure, this structure simplifies the optical structure significantly. Results of simulation and field operation indicate that this structure can not only enhance the magnetic field created by the measured current significantly, but also improve the long-term operation stability of OCT.

Abstract: Controlled partitioning strategy is one of the effective measures taken for the situation when system out-of-step occurs. The complete splitting model, mostly solved by approximate decomposition algorithms, is a large-scale nonlinear mixed integer programming problem. A new alternate optimization method based on master-slave problem to search for optimal splitting strategy is proposed hereby. The complete model was converted into master-slave problems based on CGKP (Connected Graph Constrained Knapsack Problem). The coupling between master problem and slave problem is achieved through load adjustment. A better splitting strategy can be obtained through the alternating iteration between the master problem and the salve problem. The results of the examples show that the method can obtain better splitting strategy with less shed load than other approximate algorithms, which verifies the feasibility and effectiveness of the new approach presented.

Abstract: This paper studies network security of the multi-microgrid distribution system (MMDS) composing of a large number of distributed power-islands. First, a hierarchical communication model for MMDS is designed . Then we analyze the security vulnerabilities. Finally, proposes an efficient secure key management protocol by combining Iolus framework and logical key hierarchy (LKH).

Abstract: With the continuous improvement of wind power penetration, the impact of the random fluctuation characteristics of wind power on the frequency control of the power system is growing. Currently, researchers began to study the methods of wind farms participation in frequency control to reduce the frequency adjustment pressure of other power plants and increase the wind power penetration. However, the existing simulation software for the short and long term frequency control of the power system is not so good. So in order to analyze the impact of load fluctuations or wind farm power fluctuations on system frequency control, this paper propose a frequency fluctuation simulation method based on the quasi-steady-state method.

Abstract: In recent years, there was a rapid development of wind power. The impact of large amount of wind power integration into power system on the voltage and power quality could not be ignored. The characteristic of internal dynamics of wind turbine was complicated, as a result, it could not be simulated by electromechanical transient simulation soft (BPA). It was necessary for transformation from BPA to PSCAD which was electromagnetic transient simulation program. However, the modeling work for the external power grid was enormous and meaningless. In this paper, external network was equivalent based on the BPA data of actual grid combined with PSCAD. This method not only could simulate the influence both simple and effective, but also could establish the detailed model of the regional power grid and wind power. At the same time it has been effectively used in the analysis of wind power integration into actual wind projects of Fujian power grid which achieved very good results.

Abstract: As the voltage class and transmission capacity of power grid is increasing, the operating environment of JiuAn substation, which is one of the power supply sources of Ultra-High Voltage (UHV) transmission line, becomes more complex. A model of JiuAn substation and its complicated power supply environment is built using the power system software PSCAD/EMTDC, the parameters under typical kinds of fault are simulated, and MATLAB software is used to acquire relay protection feature from the simulation results. Based on the work above, relay protection security of JiuAn Substation under complex power transmission environment is analyzed, which will provide guidance for the substation operation.