Advanced Materials Research Vols. 960-961

Abstract: The power equipments made of high-temperature superconductor (HTS) widely applied in power system in the recent years. A HTS adjustable reactor (HTS-AR) is a novel controllable reactor with the controllable windings made of HTS tapes. Shunt HTS-AR can regulate the reactive power of power and reduce the transmission loss. However, the leakage magnetic flux of the superconducting windings is relatively large, which may restrict the application of the HTS-AR in high-voltage transmission line. Basing on the research of the structure design for HTS winding, the characteristic analysis of magnetic and AC loss of HTS-AR with considering the structure of superconducting winding is shown in this study. The results show that the HTS winding with the ladder-like structure has a better performance compares with HTS winding with the solenoid structure.

Abstract: This paper aims at the problem that how to elimination the DC component of the MEMS geophone in the acquisition and processing of Seismic signal. Put forward to design a new circuit in the signal handing system. Design a new type of DC elimination circuit to eliminate the DC component through low-pass filter, reverse and other modules. The experiment result shows that, this new DC elimination circuit is easier to realize and has a large advantage than other existing DC elimination circuits.

Abstract: The combined AC+DC distribution network in this study provides a coupling and decoupling strategy of renewable energy in DC mode by using zig-zag transformer, which makes each line transmit AC electrical power and DC power simultaneously. The proposed scheme is digitally simulated with the help of Simulink software package. Simulation results indicate lower line voltage drop and less active and reactive power loss in steady state; almost similar or even better transient effects in transient state, which demonstrates the feasibility of combined AC+DC distribution network of single line interconnected with renewable energy.

Abstract: With the rapid development of smart grids, the interconnection between the grid and distributed renewable energy is the inevitable trend of future study. Because of the existence of the DC source in the combined AC-DC distribution network, the transformer iron core is easily saturated generating lots of harmonics and increasing the loss of the transformer. This paper presents a novel method based on inductive filtering technology of core saturation suppression of the transformer in the combined AC-DC distribution network, this novel method can suppress the harmonics caused by the flux saturation and forbid the harmonics intruding into the ac grid. In the end we build the simulation model to prove the correctness and practicability of this novel method.

Abstract: With the development of high voltage long distance transmission and expansion of the grid, continuous reactive power compensation devices, such as controllable reactor, become more and more important. This paper describes the design and prototype test of a high leakage reactance transformer-based high temperature superconducting controllable reactor (HLRT-HTSCR). Characteristics test results show the excellent impedance regulation characteristic of the prototype. DC critical current test of the superconducting winding shows that attention should be paid to the critical current of superconducting coil, avoiding over-current condition. This paper reveals the characteristics of HLRT-HTSCR by experiment, and will be of important practical significance to promote its development.

Abstract: Electrodes are expensive consumables of electrophysiological experiments. Cheap and homemade microwire electrodes have been widely applied, but their implantation performance is not good. To fabricate low cost and acceptable performance of microwire electrode, first, we analyzed the key factors affecting the long-term recording performance and determined the direction of the enhancement of electrode. We improved the existing fabrication process through electrode fabrication and the electrode tip surface modification, and systematically evaluated its properties, signal acquisition ability and biocompatibility. The result shows that the improved electrode tip surface is smooth and tidy, and its impedance decreased by 56.1% on average; record signal-to-noise ratio is higher; recording longevity reached 45 days; biocompatibility is better. It can meet the use of the general electrophysiological experimental, and electrode fabrication cost is less than 58 yuan.

Abstract: We report nanotesla resolution in a three-phase Metglas/FeNi/PZT-5A multiferroic composite with one end rigidly clamped operating in the first-order bending resonant mode for low-frequency magnetic field detection. Strong bending magnetoelectric (ME) couplings induced by the ununiform strain distribution in the free-clamped magnetostrictive beam are achieved without the benefit of nonmagnetic tip mass, and its natural resonant frequency is much lower than that in operating free-free mode. In addition, high-permeability materials Metgals are attached on the magnetostrictive beam for magnetic flux concentrating and resolution improvement. Experimental results reveal that the three-phase ferromagnetic/magnetostrictive/piezoelectric composite with a cantilever beam structure exhibits a high bending ME coefficient of ~32.17 V/cm·Oe at the resonant bending frequency of 819Hz under Hdc=175Oe. At the resonant excitation, the maximum resolution of 7nT is acquired under Hac=1Oe. The proposed ME cantilever structure with high resolution provideds a promising application in low-frequency magnetic transducer and sensors.

Abstract: In recent years, improved three-ratio is an effective method for transformer fault diagnosis based on Dissolved Gas Analysis (DGA). In this paper, diagonal recurrent neural network (DRNN) is used to resolve the online fault diagnosis problems for oil-filled power transformer based on DGA. To overcome disadvantages of BP algorithm, a new recursive prediction error algorithm (RPE) is used in this paper.In addition, to demonstrate the effectiveness and veracity of the proposed method, some cases are used in the simulation. The simulation results are satisfactory.

Abstract: Flicker envelope tracking is the key of analyzing voltage flicker signal. A novel method, i.e., cubic spline interpolation method is applied in the detection of the voltage flicker envelope. The typical flicker signals, such as one or multi-frequencies and frequency time-varying flicker signal are selected and analyzed by this method. Simulation results indicate that this method is effective in the detection of the envelope of voltage flicker signal. Results of one or multi-frequencies flicker signal simulation show that, when flicker frequency is less than 15Hz , the error of this method is quite tiny. The detection precision of this method is higher, especially in the scope of low frequencies of flicker and this method makes up for the disadvantage of square demodulation. Furthermore, results of frequency time-varying flicker signal simulation show that, the occurrence and recover time of voltage flicker signal can be accurately detected by cubic spline interpolation method.

Abstract: The linear regression method which will be influenced by fluctuations could only calculate constant background harmonic voltage. To make up the limitation, this paper studies partial linear method. The method expands fluctuant background harmonic voltage at a time in accordance with Taylor series. On the basis of least sum of square error, the objective function selected by the method considers the influence of weight and uses bandwidth control each size of weight. This method can calculate fluctuant background harmonic voltage accurately. A case study based on the IEEE 14-bus test system is conducted and the results indicate that fluctuant background harmonic voltage can be obtained effectively and accurately by the proposed method.