Applied Mechanics and Materials Vols. 347-350

Abstract: The dynamic circuit technology can decrease the whole power consumption, and the Floating-gate technology can simplify the circuit structure, which will also decrease the area and power consumption of IC. Taking the advantages of both ,we propose a new dynamic binary circuit based on floating-gate technology. The HSPICE simulation results using TSMC 0.35μm double-polysilicon CMOS technology validate the correctness of the proposed approach, and the proposed circuits also have considerable simpler structures.

Abstract: The signal processing circuit based on FPGA was proposed in the paper, carrying out the function such as programmable signal amplification, adaptive filtering and so on. Among them, the programmable amplifier module was achieved with the programmable gain amplifier in series; Adaptive filter module was implemented with the Butterworth second-order active filter, to change the cutoff frequency of the filter by changing the potentiometer resistance. Experimental results show that the signal processing circuit was applied in the infrared optical system improving the signal to noise ratio of the image effectively.

Abstract: Harmonic transfer between different levels of ac systems increases the difficulty in harmonic identification and governance. From the view of harmonic transfer coefficients, the paper firstly establishes a harmonic infiltration equivalent model of different voltage levels, and then analyzes the formula of harmonic transfer coefficients. Finally, the computational and simulation analysis are carried out in MATLAB software to study the factors that affect the harmonic transfer coefficients between different voltage levels.

Abstract: Capacitive commutation technology is favorable in improving the stability of weak receiving end ac systems, and our Qinghai-Xizhang HVDC interconnection project is exactly belonging to this kind. In order to study the effect of capacitor commutation technology to ac and dc systems, basing on the Qinghai-Xizhang HVDC interconnection project, the paper focuses on analyzing the building of the HVDC simulation model with capacitor commuted converters (CCC-HVDC model) in PACAD/EMTDC simulation program, and then the optimization selection of commutation capacitance parameter is described. Finally, capacitor commutated converters effect in improving the stability of weak receiving end ac system is simulated and analyzed.

Abstract: As the development of high voltage direct current (HVDC) transmission, the problems of harmonic instability become more prevalent. Besides, harmonic instability in exceedingly weak HVDC systems is particularly serious. The modulation of the DC converter based on switching function is deduced. By considering the whole process of harmonic transferring at the AC and DC side through converters from the perspective of circuit, the generation conditions of harmonic instability are analyzed. Then an exceedingly weak HVDC system model is established and simulated in PSCAD/EMTDC software to verify the theoretical analysis. The study results provide theoretical basis and computational methods to solve the problems of harmonic instability in HVDC systems.

Abstract: Therere two main methods for ultra-long distance transmission: half-wave length alternating current transmission and ultra high voltage direct current transmission. Its described in this paper that the working principle, and operational performance of both technology. In addition a comparison is made in areas of technology and performance including transmission capacity, reactive power compensation, stability and over-voltage. The parameters from the running project and theoretical prediction is used to make an economical comparison among the 1000kV half-wave length alternating current transmission and ±1000kV, ±800kV ultra high voltage direct current transmission.

Abstract: It is important to choose suitable insulator strings that matching the voltage level when trying to change an AC transmission line into a DC one. Historically based, most published works discuss the way of determining the number or the length of insulators for overhead transmission lines, which mainly consider about voltage levels, pollution classes, insulator types and their pollution performances. It calls for too much work for a line restructuring project. In order to simplify the work, a comparison of the choosing of insulator strings between AC and DC overhead transmission line is made in this paper. Two main results are obtained. One is that the ratio, which defined as α, of the number of insulator on DC transmission line and that on AC transmission line ranges from 1 to 2.5 with the decreasing of voltage level under the same pollution class, the other is that the value α remains substantially constant under the same voltage level, and it will decrease slightly as the pollution class increases. The results provide theoretical basis for the choosing of insulator strings in line restructuring projects.

Abstract: The purpose in this paper is the design of the control to switching power supply for small perturbations. By the theoretical analysis and calculation, with the output filter inductor current and filter capacitor voltage switching power supply as two state variables, the conclusion is that control of the output filter inductor current sampling do well in the anti-jamming. The simulation is made for verification. And comparing the results, the current control mode shows a very strong anti-interference ability.

Abstract: There are some traditional methods to increase AC transmission lines capacity, such as: improve voltage level, increase wire cross section area, use compact transmission line, add FACTS equipment and improve the temperature of the wire. A new method with converting ac line to dc line to increase the power capacity of AC transmission lines was put out in recent years. The fundamental principal and working characteristics of the method mentioned above are described in this paper together with the comparative analysis based on the existing experimental results and real data on technical level and economic level.

Abstract: Limitations exist when individual indexes of power quality are adopted to reflect the comprehensive level of power quality in practice. In this paper, a comprehensive analysis of the individual indexes is made to get the only parameter that can show the overall specific characterization of the power quality level. The weight values of the indexes can be calculated by combining the subjective and objective weighting methods. Combined with the principal component projection method, the projection values of the border data and the data waiting for evaluating to the ideal evaluation vector can be easily obtained. Then with the projection values, it is easy to determine the grade range where the power quality data set locates. Simulation results show that this method is effective.