Yu-Lung Ke

High-Efficiency and Low-Stress ZVT–PWM DC-to-DC Converter for Battery Charger

This work presents a novel highly efficient and low-stress battery charger with a resonant switch converter - based on resonance and zero-voltage-transition soft-switching theory - that reduces defects associated with high voltage and high current stresses caused by the resonance of traditional resonant circuits. The novel battery charger meets the requirement that all circuit components must operate with zero-voltage switching. Experimental test results indicate that the proposed battery charger reduces the temperature of an active power switch, and switching losses are less than those obtained using a traditional pulsewidth-modulation converter as a battery charger.

A Novel High-Efficiency Battery Charger With a Buck Zero-Voltage-Switching Resonant Converter

The high-frequency resonant converter has numerous well-known advantages over the traditional hard-switching converters. The most important advantage is that it offers a lower switching loss and a higher power density. Additionally, the soft-switching current waveform characterizes a lower electromagnetic interference (EMI). This study presents the circuit configuration with the least components to realize a highly efficient solar energy battery charger with a zero-voltage-switching resonant converter. The optimal values of the resonant components are determined by applying the characteristic curve and the electric functions derived from the circuit configuration. The experiment demonstrates the switching on and off of the main switches in a solar energy battery charger with a zero-voltage-switching resonant converter, wherein the switches are all operated using zero-voltage switching. The circuit efficiency in the overall charging process exceeds 80%.

Single-Stage Power-Factor-Correction Circuit with Flyback Converter to Drive LEDs for Lighting Applications

White light emitting diode (LED) with high brightness has attracted a lot of attention from both industry and academia for its high efficiency, ease to drive, environmental friendliness, and long lifespan. They become possible applications to replace the incandescent bulbs and fluorescent lamps in residential, industrial and commercial lighting. The realization of this new lighting source requires both tight LED voltage regulation and high power factor as well. This paper proposed a single-stage flyback converter for the LED lighting applications and input power factor correction. A type-II compensator has been inserted in the voltage loop providing sufficient bandwidth and stable phase margin. The flyback converter is controlled with voltage mode pulse width modulation (PWM) and run in discontinuous conduction mode (DCM) so that the inductor current follows the rectified input voltage, resulting in high power factor. A prototype topology of closed-loop, single-stage flyback converter for LED driver circuit designed for an 18W LED lighting source is constructed and tested to verify the theoretical predictions. The measured performance of the LED lighting fixture can achieve a high power factor greater than 0.998 and a low total harmonic distortion less than 5.0%. Experimental results show the functionality of the overall system and prove it to be an effective solution for the new lighting applications.

Implementation and Analysis of an Improved Series-Loaded Resonant DC–DC Converter Operating Above Resonance for Battery Chargers

The well-established advantages of resonant converters, including simplicity of circuit configuration, ease of the control scheme, low switching losses, and low electromagnetic interference, among others, have led to their attracting more interest. This work develops a highly efficient battery charger with an improved series-loaded resonant converter for renewable energy applications to improve the performance of traditional switching-mode charger circuits. The switching frequency of the improved series-loaded resonant battery charger was at continuous conduction mode. Circuit operation modes are determined from the conduction profiles. Operating equations and operating theory are also developed. This study utilizes the fundamental wave approximation and a battery equivalent circuit to simplify the circuit analyses. The mean charging efficiency of the proposed topology is as high as 87.5%.

Analysis and implementation of half-bridge series-parallel resonant converter for battery chargers

This paper presents a novel application of half-bridge series-parallel resonant converter (HBSPRC) for dc source and secondary battery interface. The converter practically eliminates both low- and high-frequency current ripple on the battery, thus maximizing battery life without penalizing the volume of the charger circuit. Moreover, operation above resonance is preferred because the power switches turn on at zero current and zero voltage; thus, the freewheeling diodes do not need to have very fast reverse-recovery characteristics. The proposed battery charger circuit has few components and low energy conversion loss, which enhance the systems overall efficiency. Circuit operation modes are determined from the conduction profiles. Operating equations and operating theory are also developed. Experimental results based on a 12V 48Ah battery charger are proposed to validate the analysis and to demonstrate the performance of the proposed approach. The maximum charging efficiency of the proposed topology during the overall charging period is 93.98%. Satisfactory performance is obtained from the measured results.

Implementation and analysis of an improved series-loaded resonant dc-dc converter operating above resonance for battery chargers

The well established advantages of resonant converters, including simplicity of circuit configuration, easy of the control scheme, low switching losses, and low electromagnetic interference (EMI), among others, have led to their attracting more interest. This work develops a highly efficient battery charger with an improved series-loaded resonant converter for renewable energy applications to improve the performance of traditional switching-mode charger circuits. The switching frequency of the improved series-loaded resonant battery charger was at continuous conduction mode (CCM). Circuit operation modes are determined from the conduction profiles. Operating equations and operating theory are also developed. This study utilizes the fundamental wave approximation and a battery equivalent circuit to simplify the circuit analyses. The mean charging efficiency of the proposed topology is as high as 87.5%.

Analysis of commutation torque ripple using different PWM modes in BLDC motors

Torque ripple generated in the commutation interval is one of the main drawbacks of Brushless DC (BLDC) motors. This paper presents an comprehensive analysis on the generated torque ripples of trapezoidal back-EMF due to phase commutation in the six switch, three-phase inverter brushless dc motor drives. Experimental results verify the amplitude of the torque ripple under 4 kinds of PWM pattern, respectively.

Power distribution system switching operation scheduling for load balancing by using colored Petri nets

This study attempts to determine the daily load patterns of service zones, line switches, distribution feeders, and main transformers by using customer information in a customer information system (CIS) and information about distribution transformers in the outage management information system (OMIS) in Taiwan Power Company (Taipower). When a power distribution system is operating under normal conditions, the reconfiguration of feeders for balancing loads among distribution feeders is obtained by the colored Petri nets (CPN) inference mechanism, which improves the operating performance of distribution systems. A practical Taiwan power distribution system, with daily load patterns derived by a load survey, is used for a computer simulation and, thus, determines the effectiveness of the proposed methodology to improve the balancing of the feeder load for distribution systems by considering the load characteristics of the service customers.

A novel single-switch resonant power converter for renewable energy generation applications

This paper develops a novel single-switch resonant power converter for renewable energy generation applications. This circuit topology integrates a novel single-switch resonant inverter with zero-voltage switching (ZVS) with an energy-blocking diode with zero-current switching (ZCS). The energy-blocking diode with a direct-current output filter filters the output stage of the novel single-switch resonant inverter. Only one active power switch is used for power energy conversion to reduce the cost of active power switches and control circuits. The active power switch is controlled by pulsewidth modulation at a fixed switching frequency and a constant duty cycle. When the resonant converter is operated at discontinuous conduction mode, the inductor current through the resonant tank could achieve ZCS of the energy-blocking diode. Accordingly, a high energy conversion efficiency is ensured. Operating principles are derived, and analyses are carried out based on the equivalent circuits for the proposed power converter under different operating modes. The operating principles of the converter were verified using a 32.4-W 70-kHz experimental photovoltaic-powered load system. Given appropriately chosen circuit parameters, the active power switch can be operated with ZVS, and a measured energy conversion efficiency of the proposed topology of 97.3% can be achieved. Experimental results demonstrate a satisfactory performance of the proposed topology, which is particularly suited to the energy conversion applications in renewable energy generation systems.

Load profile synthesis and wind power generation prediction for an isolated power system

This paper investigates the power load composition of an isolated power system using a load survey study and estimates wind power generation with a probabilistic network. The typical load pattern of various customer classes is derived, which are then used to derive the total power consumption of all customers within each class. A probabilistic neural network is used to solve the wind power generation based on the wind speed for an offshore island in Taiwan. With the hourly wind speed and load composition, the power generation of diesel generators was obtained. Results of this paper demonstrate that wind power generation can economically and effectively replace the power generation of the islands diesel power plant and provide partial power-supply capability for the net peak load requirement.