Ping-Lin Fan

A fault detection and faulted-phase selection approach for transmission lines with Haar wavelet transform

Wavelet transform is a novel signal processing technique and has been widely used in many applications, including power system disturbance analysis. Many published works introduce the wavelet transform as a tool to analyze power system disturbances. In this work, a dyadic wavelet transform based approach, which is used to detect transmission line faults, is proposed. The coefficient of discrete approximation of the dyadic wavelet transform with Haar wavelet is used to be an index for transmission line fault detection and faulted-phase selection. Basic ideas and the proposed algorithm are described in this paper. MATLAB/Simulink is used to generate fault signals and verify the correctness of the algorithm. Simulation results reveal that the performance of the proposed fault detection indicator is promising and easy to implement for computer relaying application.

Mechatronic experiments course design: a myoelectric controlled partial-hand prosthesis project

This paper describes a proposed laboratory project involving the design of a myoelectric-controlled partial-hand prosthesis to reinforce mechatronic education. The proposal focuses mainly on extract electromyogram (EMG) signals generated during contraction of the biceps. The EMG signals are first amplified and filtered by a laboratory-designed electronic circuit and then reprocessed using a microcontroller to drive the servomotor so that the designed prosthesis can be properly controlled. The project introduces students to component-level and system-level design and exposes them to the integration of a microcontroller, electronic circuits, sensors, and prosthesis mechanisms. Moreover, since the project results in a working prosthesis, student enthusiasm for mechatronic education increases, and they see its relevance to the field in applied engineering. Implementation of the laboratory project within the curriculum has been demonstrated to be highly motivational and educational and has even helped to attract more students to study mechatronic applications.

A composite index to adaptively perform fault detection, classification, and direction discrimination for transmission lines

This paper presents an adaptive protection scheme for transmission lines based on synchronized phasor measurements. The work includes: fault detection, fault classification, and fault direction discrimination. Using two-terminal synchronized measurements incorporated with distributed line model and Clarke transformation theory, fault detection index is derived. We can classify the faults by the proposed modal fault detection index and the circuit breaker can achieve single-pole tripping. The fault detection index is composed of two complex phasors. The fault events can be found according to the angle difference between these two phasors as in internal and external fault situation. The proposed method also combines on-line parameter estimation to assure protection scheme performance and to achieve adaptive protection. After a lot of EMTP simulations and verifications show that the method provides a fast and accurate protection scheme for transmission lines. The tripping decision time of the protective relay is within 1/2 cycle.

Electroluminescence Phenomena in InGaN/GaN Multiple Quantum Well Light-Emitting Diodes with Electron Tunneling Layer

The phenomena of electroluminescence in InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) with an n-AlGaN layer and a superlattice of 10 periods of InGaN (10 A)/GaN (15 A) serving as the electron tunneling layer (ETL) have been investigated in detail over a broad temperature range from 20 to 300 K at various injection currents. Compared with conventional LEDs with a well-designed ETL, quantum efficiency and temperature insensitivity are found to be improved when an n-AlGaN layer is inserted. This is attributed to the localization effect of the n-AlGaN layer being stronger than that of the ETL layer, as analyzed using the Varshini formula and band-tail model. Nevertheless, the inserted ETL layer with the purpose of improving the carrier injection into the active layer not only increases the carrier recombination quantity, which leads to a marked increase in output light emission intensity, but also reduces the light emission intensity compared with sample with the n-AlGaN layer. Consequently, inserting a blocking layer between an active layer and a p-GaN layer may increase the output light emission intensity of the sample with an ETL.

Focal length measurement by the analysis of moiré fringes using the wavelet transformation

Abstract A novel method, where moiré patterns, produced by the images of reference gratings, and a CCD pixel array are used to measure the focal length of a lens is presented. The tested lens could magnify the images of straight‐line gratings onto the CCD camera. The positions of the lens being tested were moved so as to arrange that the pitch values between the reference grating images and the lattices of the CCD camera were similar. This generates moiré fringe images. Due to the structure of the lens system, it is always hard to identify the pitch value of the CCD lattice gratings accurately or what would be the distance between the gratings and the CCD arrays where moiré fringe images formed. Our method, in which micro‐stages were used to precisely measure the displacement of the tested lens, and a one dimensional wavelet transform algorithm was applied to estimate the pitch values of the moiré patterns, could avoid these obstacles. Compared to those systems also based on moiré effects but using coherent light sources, our optical setup is less expensive, easier to implement and has an acceptable accuracy.

Thickness-dependent renormalization of strain effects on self-organized InAs quantum dots grown on GaAs

The thickness-dependent renormalization of strain effects on self-organized InAs quantum dots has been systematically investigated. The photoluminescence-emission energy shift for the smaller quantum dots reveals both the hydrostatic and shear strain effects. However, the characteristics of the larger quantum dots are attributed predominantly to the hydrostatic effect. Furthermore, due to the elastic stiffness constant difference, the GaAs matrix-dependent characteristics were prevailed in the smaller quantum dots, while InAs-like properties were observed in the larger ones. All results indicate that the strain effect plays a major role in the emission energy of InAs quantum-dot heterosystems.