Yi-Hwa Liu

Search for an optimal rapid charging pattern for lithium-ion batteries using ant colony system algorithm

Commercial lithium-ion batteries are playing important roles as supplies for mobile phones, laptop computers, and other electronics. In order to maximize the performance of lithium-ion batteries, an advanced rapid charging pattern is required. In this paper, an Ant-Colony-System (ACS)-based algorithm is presented. The proposed ACS-based algorithm can be integrated into a commercially available battery tester to search for the optimal rapid charging pattern. Experimental results show that the obtained rapid charging pattern is capable of charging the lithium-ion batteries to 70% capacity in 30 min. The obtained pattern also provides 25% more cycle life than the conventional constant current-constant voltage method.

Search for an Optimal Rapid-Charging Pattern for Li-Ion Batteries Using the Taguchi Approach

Lithium-ion batteries are playing important roles as energy storage solutions for portable devices, automotive electronics, and renewable energy systems. In order to maximize the performance of lithium-ion batteries, an advanced rapid-charging pattern is required. In this paper, a Taguchi-based algorithm is presented. Orthogonal arrays are implemented to determine the optimal rapid-charging pattern for multistage constant-current (CC)-charging method. Experimental results show that the obtained rapid-charging pattern is capable of charging lithium-ion batteries to 75% capacity in 40 min. The obtained pattern also provides 60% more cycle life than the conventional CC-constant-voltage method.

A Modified PI-Like Fuzzy Logic Controller for Switched Reluctance Motor Drives

Based on the redevelopment of control rule base, two modified PI-like fuzzy logic controllers with output scaling factor (SF) self-tuning mechanism are proposed and verified in this paper for application in the switched reluctance motor (SRM) drive system. The motivation of this paper is to simplify the program complexity of the controller by reducing the number of fuzzy sets of the membership functions (MFs) without losing the system performance and stability via the adjustable controller gain. For both types of controllers, the output SF of the controller can be tuned continuously by a gain updating factor, whose value is derived from the fuzzy logic reasoning, with the plant error and the error change ratio as the input variables. The rule bases are created based on the knowledge of the SRMs dynamic behavior and practical experience. Various aspects of the design considerations about the MF, rule base, and gain tuning strategy are described in detail. Experimental results, carried out on a four-phase 8/6-pole SRM based on the dSPACE DS1104 platform, are given to show the feasibility and effectiveness of the devised methods. A performance comparison of the proposed controllers with their conventional counterpart is also included.

Software-Reconfigurable e-Learning Platform for Power Electronics Courses

An effective course in power electronics should ideally contain hands-on design and experimental work as well as theory explanation and simulations. In this paper, a software- reconfigurable e-learning platform for power electronics courses is proposed. The aim of the proposed system is to realize a platform capable of constructing a wide range of circuit topologies and control techniques, thus enabling students to gain a better understanding of power electronics converters through practical experiments. The proposed platform consists of a reconfigurable power electronics testbed, a Web-based distance laboratory, and a user interactive e-learning platform. The reconfigurable power electronics testbed can be configured by the students via a Web- based interface to construct a wide variety of converters and inverters. The Internet accessible distance laboratory system permits the instructors and students to remotely conduct experiments over the Internet. The integrated interactive multimedia material can support the educational environment of power electronics courses and can be executed on any modern personal computer (PC) without additional hardware. The advantages of the proposed platform include flexibility, friendly user interface, allow for distance waveform measurements, and removal of laboratory time and space constraints. The positive response from students indicates that the proposed platform is extremely useful for power electronics courses.

Design and Implementation of an FPGA-Based CCFL Driving System With Digital Dimming Capability

The proliferation of liquid-crystal display (LCD) monitors and notebook computers places an ever-increasing demand on display technology. The LCD with cold cathode fluorescent lamp (CCFL) best satisfies display performance, size, and efficiency. To operate the CCFL, a driving circuit is needed to light the lamp with a relatively high voltage and then stabilize the arc current. For minimizing the component count and size, a high-frequency zero-voltage switching (ZVS) resonant converter is preferred. In this paper, a field-programmable-gate-array-based ZVS resonant converter for driving CCFL with digital dimming capability is presented. The proposed digital controller utilizes the pulse density modulation technique to adjust the output power. A 3-W prototyping system is built and tested; experimental results show that the proposed system can reduce the voltage spike by more than 15%, compared to the low-frequency dimming methods. The overall system power efficiency is approximately 85%. The advantages of the proposed system include high efficiency, low output voltage and current spike, wide dimming range, flexibility, and compactness.

High-Power-Factor Electronic Ballast With Intelligent Energy-Saving Control for Ultraviolet Drinking-Water Treatment Systems

Over the past few decades, ultraviolet (UV) water treatment has become widely recognized and accepted by regulatory agencies as a proven disinfection process. With the increased awareness of health concerns and water quality, UV disinfection is quickly gaining popularity in the consumer market as a safe, effective, and economical approach to disinfection. In order to disinfect properly, conventional UV water-treatment systems keep their light intensity at maximum level regardless of the operating condition; this results in unnecessary energy waste along with lamp-life-span reduction. In this paper, a new design of high-power-factor low-cost electronic ballast with intelligent control for UV water-treatment system is proposed. For the purposes of energy saving, an intelligent-control algorithm is proposed to dim the luminance of the UV lamp according to the measured water flow rate and UV light intensity. Accurate knowledge of the characteristics of the UV lamps is essential for the ballast design. Therefore, an automatic identification system is also proposed in this paper to obtain the characteristic parameters, which are the dynamic and steady-state profiles of the UV lamps. Systematic design procedures are then presented accordingly. The proposed UV water-treatment system boasts the advantages, such as compactness, low cost, and energy saving, and is suitable for residential users. According to the experimental results, the energy-saving capability of the proposed system is better than 50%.

An FPGA-based lithium-ion battery charger system

Nowadays, the number of portable electronics products such as mobile telephones and laptop computers has grown explosively. These developments have resulted in massive demand for secondary batteries. The advantages of lithium-ion batteries include no memory effect, high operation voltage, and high energy density. Therefore, it is the most popular secondary battery for consumer electronics. In this paper, a FPGA (field programmable gate array)-based lithium-ion battery charger system is developed. The concerned charger system consists of an FPGA-based controller, a data acquisition system and a programmable power source. The proposed system can achieve the goals such as digital programmability, user-friendly interface, data monitoring ability and stable voltage/current source. According to the experimental results, the proposed charger system is capable of charging the lithium-ion batteries with less than 1.5 % current ripple.

Digital dimming control of CCFL drive system using pulse density modulation technique

In this paper, a digital dimming controller for the CCFL drive system is presented. The proposed digital controller utilizes pulse density modulation (PDM) technique to adjust the output power. In order to verify the correctness of the proposed method, a FPGA (Field Programmable Gate Array)-based CCFL drive system is also built and tested. The overall system power efficiency is approximately 85%. Comparing to low frequency dimming (LFD) methods, the proposed system can reduce the voltage spike by over 15%.

Novel Modulation Strategies for Class-D Amplifier

Recent advances in semiconductor technology have renewed interest in class-D audio amplifiers, especially for portable devices and consumer electronics. In addition to higher efficiency, class-D amplifiers are smaller, lighter, streamlined, cool and quiet with extended battery life compared to the conventional linear amplifiers. A typical class-D amplifier increases the efficiency of amplifiers in consumer and professional applications from the industry norm of approximately 50 percent to 90 percents or better. In this paper, two zero voltage switching (ZVS) modulation strategies are proposed to achieve the goals of high fidelity and high efficiency. Field programmable gate array (FPGA) implementations of the proposed modulation strategies are also provided in this paper. In order to verify the correctness of the proposed methods, a FPGA-based class-D audio amplifier prototype is developed and realized. Experimental results are then presented to validate the proposed modulation strategies. According to the experimental results, the proposed test system is able to deliver more than 15 W into a 4 Omega load with an efficiency of 80% and total harmonic distortion (THD) less than 2 %.

Application of the ant colony system for optimum switch adjustment

In this paper, a co-operative agent algorithm, the ant colony system, for optimum switch adjustments is proposed. Switch adjustment is one of the most important tools for distribution automation, since it can improve the system reliability and reduce the interruption costs without additional capital investments. The formulation of switch adjustment is a combinatorial optimization problem with nonlinear and nondifferential objective function. In this paper we choose the ant colony system to solve the problem since the ant colony system has the characteristics of positive feedback, distributed computation and the use of a constructive greedy heuristic. One of the main goals of the paper is to investigate the applicability of the ant-colony-system-based algorithm in the power system optimizations. Test results show that the proposed ant-colony-system-based algorithm can offer an optimum solution for switch adjustment.