Tạp chí Phát triển Khoa học & Công nghệ: Kỹ thuật & Công nghệ

Nghiên cứu phương pháp phát hiện, định vị, cô lập sự cố và khôi phục cung cấp điện cho lưới điện phân phối thông minh

Lê Duy Phúc, Bùi Minh Dương, , Đoàn Ngọc Minh, Huỳnh Công Phúc, , Đỗ Minh Hải — Mon, 13 Jul 2020 00:00:00 +0700

The smart grid model has been determined in recent years, which is included the smart distribution network field. The application of self-healing technology in the smart distribution network is one of the most important problems needed to be solved to enhance the reliability indexes of implemented areas. When a fault occurs, FLISR tool will quickly detect and locate the fault segments accurately before implementing calculation, analysis and proposing isolation and service restoration plans which minimize the amount of lost power or outaged customers at power supply interrupted areas. This research proposes a method based on fault indicated signals from FTU, FI that can help FLISR tool quickly detect and locate the fault segments within a short-time process. Then, the FLISR tool will analyzes, evaluates and ranks the isolation and service restoration plans based on two main constraints included: restoring the possible maximum number of out-of-service loads; and (ii) limiting the minimum number of switching operation. An experimental result is used to validate the FLISR approach proposed for a real 22kV distribution network.

Tối ưu hóa vị trí nhiều thiết bị D-Statcom nhằm cải thiện chỉ tiêu SARFIX trong lưới phân phối

Bạch Quốc Khánh — Mon, 13 Jul 2020 00:00:00 +0700

While the users only consider solutions for power quality improvement at a single site, utilities concern about solutions for power quality improvement for not only an individual location, but also for the whole system. Therefore, the paper deals with an utilities' systematic solution for power quality mitigation by using simultaneously a number of custom power devices in distribution system. In the paper, a new method is introduced for optimizing the placement of a multiple of Distribution Synchronous Compensation Devices - D-Statcoms for globally mitigating the voltage sags due to faults in distribution systems according to the ``central improvement'' approach. D-Statcom's placement is optimally selected in a distribution system basing on a problem of optimization where the objective function is to minimize the system average rms voltage variation frequency index – SARFIx of the system of interest. The effectiveness for global voltage sag mitigation in a distribution system by the presence of a number of D-Statcoms is newly modeled basing on the method of Thevenin's superimposition in the problem of short-circuit calculation in the distribution system. The presence of D-Statcoms is simulated as the matrix of additionally injected currents to buses for increasing the voltage of all buses throughout the system of interest. The paper considers the case of using a multiple of D-Statcoms with a proposed voltage compensating principle that can be practical for large-size distribution systems. In the paper, the IEEE 33-buses distribution feeder is used as the test system for global voltage sag simulation in the events of short-circuit in the system and various influential parameters to the outcomes of the problem of optimization such as rms voltage threshold and D-Statcom's limited current are considered and discussed.

Giải pháp mới nâng cao hệ số công suất và giảm tổng độ méo dạng sóng hài trong bộ nguồn hai tầng cho đèn Led

Mon, 13 Jul 2020 00:00:00 +0700

Nowadays, the incadescent, florescent, and high-pressure mercury lamps was replaced by the LED (Light-Emitting-diode) …due to the high efficiency, enviromenttally friendly and long life-time. This paper presents an analysis and experimentation on 250W LED Driver with high power factor and improving the toral harmonic distortion. The presented topology in this paper is designed based on two-stage LED Driver which is included: the boost power factor correction circuit operating in discontinuous mode and an isolated DC/DC LLC resonant circuit with soft-switching characteristics. The function of the boost power factor correction stage is to ensure the high input power factor and to generate 400VDC from variable AC power supply: 140VAC to 260VAC. The target of the DC/DC stage is to control the DC current for supplying LED load. The guideline for design is in detail described. A LED Driver prototype was built in laboratory for supplying 250W/54V from single phase AC power supply 220V/50Hz. The experimental results are shown to verify the performance of the LED Driver comply with the EN 61000-3-2 standard.

Phương pháp mới bôi keo đế dép cao su với bề mặt phức tạp

Lưu Thanh Tùng — Mon, 13 Jul 2020 11:39:34 +0700

Nowadays, people often wear shoes or slippers when going outside. Rubber slippers are very popular in the world, especially in tourist area. Rubber slippers can be easily seen at tropical countries such as Vietnam. A slipper consists of many layers, and they are glued and then pressed to ensure them not to be separated during retention period. In the past, the layers of slippers is glued by rollers because the surfaces of layers are flat and simple. However, the slippers are now improved and then the surfaces of layers become complicated and difficult to spread the glue. The surface is produced by curved faces matching with the foot. Therefore, the workers have to use a brush to spread the glue on the surfaces, especially the line of intersection of surfaces. The rollers are tried but the result is so bad because the glue cannot reach the intersection of two faces on the surface of the slipper. The places without the glue will make the slipper become failure after used. In this paper, although the rollers are also applied, the rotational speed of these rollers are different. The different speed helps the glue spread to be same as glued by hand. The number of rollers is determined by experiment. The ratio of rotational speed and the gap between two rollers are also showed by experiment to obtain a best result of the glue spread. All of the experimental data will be shown by graphs helping the readers to understand more clearly about the best parameters for machine operation. Results from this paper are foundation for designing a real gluing machine which helps shoe manufacturing industry to develop.

Hệ thống định vị trong nhà trên nền tảng BLE sử dụng phương pháp định vị MiRingLA

Lê Văn Hoàng Phương, Trương Quang Vinh — Mon, 13 Jul 2020 11:44:24 +0700

Over the past decades, locating and navigating to the departments and wards in a large hospital have never ceased to draw public attention. A large number of human-based efforts and solutions have been given to deal with the difficulty in location and navigation in a large hospital. However, the problem is still existing, which urges human to take technology into account seriously. In this context, an indoor positioning system comes into play, it can not only tackle the trouble but also act as a prospective platform to build other applications on top of it. Nonetheless, the ever-changing environment and the heavy dependence on installation stage have precluded many state-of-theart methodologies from practice. In this paper, we present an indoor positioning system based on Bluetooth Low Energy and applied to hospitals, which is easy-deployed, robust in the noise-rich, obstacle-rich environment. The system provides 3 principal functions like new medical examination registration, patient's in-app schedule management, and navigation. We implemented a web application to realize the first function. Besides, an Android application was developed to put ability up for patients to manage schedules and find ways. Moreover, we proposed a positioning method that is a modification to inter Ring Localization Algorithm (iRingLA), called MiRingLA. It utilizes 3 rings and Least Squares Estimation to deal with the drawback of the iRingLA. In addition, we applied a Kalman filter to reduce noises from received signals. The proposed method was experimented in a practical environment and achieved the mean localization accuracy of 0.91 m. Moreover, we performed comparisons between our proposed method and some of the others. Our proposed scenarios were experimented and proved to be feasible and suitable for a real application.