Chin-Sien Moo

Harmonic analysis for industrial customers

A power flow program is developed to analyze the harmonic distortion of a power system with various types of harmonic loads. The proposed program can be applied to solve the harmonic current flow, voltage harmonic distortion factor, resonance frequency, and current amplification factor at every bus in the system. In this study, a large metal factory is selected for the harmonic power flow analysis. The current waveforms at every bus are measured and analyzed to determine various orders of harmonic components. These harmonic currents are used in the computer simulation to determine the harmonic voltage distortion factor at the buses of the system, and the variations of resonance, impedance, and amplification factor with frequencies are investigated. The program is used to calculate the harmonic load flow when the metal factor is expanded by including a new plant in the power system, and proper filters are designed to alleviate the harmonic problems.<<ETX>>

Charge equalization of battery power modules in series

Battery power modules (BPMs) with associated power converters are connected in series to comply with a high load voltage. With bidirectional power converters, BPMs can perform buck conversion for the charging operation. The continuous conduction mode (CCM) and the discontinuous conduction mode (DCM) of buck converters in series are analyzed. According to the analyzed results, an equalization strategy is proposed to solve the charge imbalance problem by scheduling the individual battery current. Experiments are carried out to demonstrate the effectiveness of the balance charging method.

A Novel Single-Stage High-Power-Factor Electronic Ballast with Boost Topology for Multiple Fluorescent Lamps

A novel single-stage high-power-factor electronic ballast with boost topology for multiple fluorescent lamps is presented in this paper. A high power factor at the input terminal is achieved by operating the boost converter in discontinuous conduction mode. With carefully designed circuit parameters, soft switching on the power switches of the resonant inverter can be retained to attain high circuit efficiency. A prototype electronic ballast designed for four 20 W fluorescent lamps is built and tested to verify the analytical predictions. Satisfactory performance is obtained from the experimental results.

High-power-factor electronic ballast with self-excited series resonant inverter

This paper presents a simple configuration of a high power factor electronic ballast. The proposed approach makes an integration of two power processing stages, a boost power converter and a self-excited series resonant inverter. The self-excitation mechanism makes a merit of self-adjustment on the inverter duty-ratio resulting in an almost unity power factor at the input line. Experimental tests are carried out an the circuit designed for a 36-W compact fluorescent lamp.

Balanced discharging for serial battery power modules with boost converters

A group of boost-type battery power modules (BPMs) are connected in series to cope with a higher output voltage. The operations of BPMs in series are mutually interactive. However, all batteries in the BPMs can substantially be discharged individually so that they can realize the balanced discharging control strategy, by which the battery currents are scheduled in accordance with their state-of-charges (SOCs). A battery power source formed by 10 boost-type BPMs is built and tested. Each BPM employs an associated micro controller for detecting the load voltage, estimating the SOCs, and controlling the duty ratios of the power converters. Experimental results demonstrate the balanced discharging capability of the serial BPMs.

Detection of acoustic resonance in metal halide lamps

To understand the occurrence of acoustic resonance in metal halide lamps is essential for an engineer to design a high-frequency electronic ballast. This paper proposes a simple method by measuring the lamp voltage for detecting the acoustic instability instead of observing the lamp arc by human eyes. The standard deviation in the lamp voltage is used as an index to determine the occurrence of acoustic resonance. With the index, the degree of the lamp arc instability can easily be specified. Experiments are carried out on various 70 W lamps to inspect the influence of the lamp type, the used hours, and the operating power on the frequency spectra of acoustic resonance.

An efficient driver for dimmable LED lighting

An efficient driver circuit is proposed for light-emitting-diode (LED) lamps with a dimming feature. The driver consists of a flyback converter in series with the dc-link. By processing partial power of the driver circuit for current regulation, the loss produced by power conversion can be diminished. The dimming feature is accomplished by means of current amplitude modulation (AM) or double pulse-width modulation (DPWM). The detailed circuit operation stages and analysis are provided. A laboratory circuit is designed for a 45 W LED lamp. Experimental results demonstrate that a high efficiency can be achieved, even at dimmed lamp power.

Designing an ignitor for short-arc xenon lamps

A compact ignitor is designed for short-arc xenon lamps which require high ignition voltage and fast transition. The ignitor employs two stages of step-up circuits with two small sized transformers. A capacitor with an intermediate voltage is used for storing the energy converted from the DC power supply by the first-stage step-up circuit. The impact voltage necessary for igniting the xenon lamp is generated by the second-stage step-up circuit which is connected in series with the lamp and the DC power supply. The design of the ignitor for a short-arc xenon lamp of 350 W is discussed as an illustrative example.

A new power-factor-correction circuit for electronic ballasts with series-load resonant inverter

This paper presents an efficient, small-sized and cost-effective power factor correction (PFC) scheme for high-frequency series-resonant electronic ballasts. The proposed scheme introduces additional small energy tanks processing partial power and thus can perform the function of input current shaping. Theoretical and experimental results prove that the electronic ballast incorporating with only few reactive components can achieve nearly unity power factor and very low harmonic distortion.

Operation of battery power modules with bidirectional DC/DC converters

A battery power system can be assembled by a number of battery power modules (BPMs) to higher voltage and current in addition to provide a higher sustainable energy. In which, the battery sets are equipped with associated power electronic converters to regulate the conversion power as well as the output voltage and current. When a bidirectional power converter is adopted in a BPM the battery set is charged and discharged through the same port. Three bidirectional dc-to-dc converters used for BPMs are analyzed. The charging and discharging operations are illustrated by an exemplar battery power source with four serial boost/buck type BPMs.