Applied Mechanics and Materials Vols. 644-650

Abstract: The LCL filter is easy to resonate, especially in the new energy power system with multiple inverters. The LCL filter resonant formulas are derived in this paper and a novel double closed loop control strategy combing with the structure of the LCL filter was proposed at the base on feedback of capacitor current as a result. In the control system, the inner loop feedback the first differential voltage of filter inductor at the grid side to damp the resonance and nature of first differential voltage of filter inductor is explained; the grid current outer loop achieves direct control of the grid current for high power factor and utilization efficiency. The simulation results show that the grid-side inductor voltage differential feedback control have a better current control effect both in the condition of the normal power grid voltage and distorted grid voltage, and the fluctuations of power and dc voltage are reduced.

Abstract: There are many kinds of mobile power supply, in this paper, aiming at the existing mobile power cannot be automatically continued charging problem, an automatic charging and discharging circuit design, and put forward the improvement circuit corresponding to the common lithium battery over-voltage and over-current protection, battery monitoring problem. The widespread use of application of STC15W401AS, SX2105, DS2762 chip as the core device, with the corresponding peripheral circuit, provides a reference for the application of charge power supply protection circuit of lithium ion batteries based on SCM system.

Abstract: Making assessment of risk factors of power transformer life cycle cost modeling is an important mean of improving the scientificity of transformer life cycle cost management. Considering the risk factors of transformer life cycle cost, this paper presents risk assessment index system of transformer life cycle cost, applying matter-element model and extension analysis theory to quantify the qualitative indexes in order to assess the risk. Combined with an example, the paper quantifies the uncertain factors of power transformer life cycle cost management in order to build the life cycle cost risk assessment system. It realizes the risk rating of the transformer cost assessment, getting the key risk factors which affect transformer cost so that we can put forward targeted control strategies according to various risk factors in practical engineering.

Abstract: The problem of transient stability of power system is one of the most actively studied nowadays. Classifiers have been applied to the transient stability assessment (TSA) and shown great potential. This paper proposed an adaptive combined classifier based on back-propagation neural network (BPNN) and support vector machine (SVM). In this method, gray area with low accuracy was found by output of BPNN, but it can be improved in SVM. Experiment results on New England system demonstrate the accuracy and speed of proposed classifier.

Abstract: Moisture has a detrimental effect on oil-paper insulation life by lowering electrical breakdown strength. How does the space charge behavior of the oil-paper insulation system consisted by oil gap and oil immersed insulation pressboard with different moisture content The space charge characteristics of the mixed insulation consisted of oil gap and pressboard with three moisture content were investigated using the PEA measurement system. The space charge accumulation behaviors at the interface between oil gap and pressboard were analyzed. The distortion of the electrical field in the oil gap and pressboard was also analyzed. Results show that there are many charges injected into the oil and the pressboard. The charges accumulated at the interface between oil gap and pressboard. The charges accumulated in the mixed insulation system become less with the moisture content increased. The difference of the electric field strength in the oil gap and pressboard become smaller with the moisture content increased.

Abstract: Resistivity is an important parameter to determine the electrical properties of semiconductor materials, which can be obtained from four-probe measurement to get the doping concentration and other important information. This paper gives an introduction of an intelligent DC four-probe meter based on Micro-Controller Unit (MCU), including the principle, the overall framework and the function of each module. The design of hardware and software of the system are described. This instrument has the advantages of miniature size, modular structure, strong anti-interference ability and low power consumption.

Abstract: Wide-area protection is extensively used in power system. The fundamental of this protection scheme is the communication system and its routing selection. The wide-area communication network requires not only high reliability, but also rigid latency limit. To solve this problem, a routing selection method is proposed, considering availability and latency. A backup path is also taken into account to rebuild connection in case of communication path failure. With the case study, the method is proved to be simple and accurate. It can provide the join with the most reliability, on the premise of proper latency.

Abstract: A single resonance frequency is the main factor of limiting vibration energy collector efficiency. In this paper, the multi degree of freedom oscillation adjusting bandwidth scheme is reported, designing a kind of new broadband vibration energy harvester, which has multi-mode energy acquisition, multi freedom vibration and broadband characteristics. Firstly, Broadband energy collector structure design. Secondly, Combining with the main vibration form, using the ANSYS carried out a detailed analysis of its working model. Finally, designing the prototype and doing some experimental verification, the results show that the designed energy collector with low frequency and wideband energy acquisition performance, the frequency domain of energy collection is 57.6 to 69.45HZ ,which break through the bottleneck of traditional single resonance frequency of energy acquisition, has a high value of theory and engineering application.

Abstract: In this paper, application of planar transformers in TWTA (Travelling-wave Tube Amplifier) is investigated and a method of equivalent circuit is used to study performance of planar transformers. The lumped parameters of planar transformers are extracted by FEM (Finite Element Method).

Abstract: A reconfigurable radix-r FFT structure design is proposed, to reduce the memory and time consumption caused by zero-paddling in traditional radix-2/4 methods. The radix-r FFT computing flow is divided into three iterative steps: rotate factors computation; memory access schedule; butterfly coefficients matrix multiplication. The hardware structure is depicted, in which the memory accessing schedule is implemented by a finite state machine, the rotate factors and butterfly coefficients are calculated by the Taylor series expansion. The time consumption of the proposed structure is analyzed, and with the arbitrary data points, an optimized radix can be used to minimize the computing time. Compared with traditional methods, the proposed design has the advantage of generality, less time consumption and hardware costs.