13 results on '"Forsyth, Andrew J."'
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2. High-performance multipulse rectifier with single-transistor active injection
- Author
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Araujo-Vargas, Ismael, Forsyth, Andrew J., and Chivite-Zabalza, F. Javier
- Subjects
Electric current rectifiers -- Design and construction ,Rectifier instruments -- Design and construction ,Metal oxide semiconductor field effect transistors -- Design and construction ,Pulse-duration modulation -- Methods ,Waveforms -- Evaluation ,Power electronics -- Research ,Business ,Electronics ,Electronics and electrical industries - Abstract
A three-phase, multilevel rectifier using active voltage injection with one MOSFET device is presented. The injector consists of a bidirectional switch that modifies the behavior of a 12-pulse rectifier resulting in either 24-pulse or multilevel pulsewidth-modulated (PWM) operation. The resultant input currents are almost sinusoidal, the line current THD being 2.36% for 24-pulse operation and 1.06% for PWM operation. The MOSFET current is 2.9% of the load current. The circuit operation, idealized waveforms and modulation strategy are explained and experimental results are presented. Index Terms--High-power factor rectification, three-phase multipulse rectifier.
- Published
- 2008
3. A passive 36-pulse ac-dc converter with inherent load balancing using combined harmonic voltage and current injection
- Author
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Chivite-Zabalza, Fco. Javier and Forsyth, Andrew J.
- Subjects
Electric current converters -- Design and construction ,Load balancing (Computers) -- Analysis ,Harmonic analysis ,Electric current converter ,Load balancing ,Business ,Electronics ,Electronics and electrical industries - Abstract
A combination of two, simple, passive injection circuits is used to eliminate virtually all the low-order harmonics from the line currents of a standard 12-pulse rectifier, transforming its performance into that of a 36-pulse system. A line current total harmonic distortion of 1.51% is achieved in a 15-kW, 400-Hz prototype. The basic 12-pulse rectifier comprises two 6-pulse bridges that are series connected on both the ac and dc sides along with a 50 %-rated, delta-star, phase-shifting transformer, while each injection circuit principally consists of a small transformer that operates at six times the supply frequency and carries around 1% of the total power throughput. The injection techniques are also valid for a fully isolated transformer arrangement. Full details of the circuit operation and design are reported. Index Terms--Total harmonic distortion (THD).
- Published
- 2007
4. A simple, passive 24-pulse ac-dc converter with inherent load balancing
- Author
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Chivite-Zabalza, F. Javier, Forsyth, Andrew J., and Trainer, David R.
- Subjects
Electric current converters -- Design and construction ,Electric current converters -- Mechanical properties ,Electric current converters -- Analysis ,Electric circuits -- Analysis ,Electric current converter ,Business ,Electronics ,Electronics and electrical industries - Abstract
A new converter topology for a three-phase multi-pulse rectifier circuit is described. This converter draws almost sinusoidal currents from the ac system with very low harmonic content and typically less than 3% total harmonic distortion. The topology uses only passive components and has a lower component count than other rectifier circuits with similar performance. Two six-pulse rectifier bridges are connected in series, fed by a series connection of transformers, to form a 12-pulse system. An additional low power harmonic injection circuit enhances the performance of the circuit to obtain low harmonic current pollution levels that are comparable with those achieved from a 24-pulse rectifier. The circuit operation is explained and experimental results are presented. Index Terms--Autotransformers, rectifier bridges, sinusoidal currents, three-phase multipulse rectifier circuit.
- Published
- 2006
5. Extended fundamental frequency analysis of the LCC resonant converter
- Author
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Forsyth, Andrew J., Ward, Gillian A., and Mollov, Stefan V.
- Subjects
Capacitors -- Research ,Electric current converters -- Research ,Electric current converter ,Business ,Electronics ,Electronics and electrical industries - Abstract
Fundamental frequency techniques are used to analyze the series-parallel resonant converter under heavy load conditions, both with a continuous, but distorted parallel capacitor voltage waveform, and with a discontinuous capacitor voltage waveform. The analysis is validated with results from an experimental prototype. The application of the technique to the parallel-loaded L-C resonant converter is also considered. Index Terms--Converter, dc-dc converters, parallel capacitor, series-parallel, voltage waveform.
- Published
- 2003
6. A high-power-factor, three-phase isolated ac-dc converter using high-frequency current injection
- Author
-
Cross, Andrew M. and Forsyth, Andrew J.
- Subjects
Electric current converters -- Research ,Electric current converter ,Business ,Electronics ,Electronics and electrical industries - Abstract
A single-stage, three-phase ac-to-dc converter topology is proposed for high-frequency power supply applications. The principal features of the circuit include continuous current operation of the three ac input inductors, inherent shaping of the input currents, resulting in high power factor, a transformer isolated output, and only two active devices are required, both soft-switched. Resonant conversion techniques are used, and a high power factor is achieved by injecting high-frequency currents into the three-phase rectifier, producing a high frequency modulation of the rectifier input voltages. The current injection principle is explained and the system operation is confirmed by a combination of simulation and experimental results. Index Terms--AC-DC power conversion, harmonic analysis, harmonic distortion, power electronics, resonant power conversion.
- Published
- 2003
7. An Analysis of the Thermal Interaction Between Components in Power Converter Applications.
- Author
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Shahjalal, Mohammad, Ahmed, Md Rishad, Lu, Hua, Bailey, Chris, and Forsyth, Andrew J.
- Subjects
THERMAL analysis ,POWER electronics ,CONVERTERS (Electronics) ,SEMICONDUCTOR devices ,ELECTRIC current rectifiers ,COOLING systems - Abstract
Accurately predicting the temperature of semiconductor devices is very important in the initial design of the power electronics converter. RC thermal models derived from the well-known methods have some ability to predict the temperature. However, the accuracy is boundary condition specific; hence, these methods cannot be used in the reliability analysis. To make the thermal model more accurate and robust, the factors contributing to discrepancies need to be analyzed carefully. These are power-module-materials’ nonlinear properties, thermal grease layer, and the cooling system (i.e., liquid-cooled cold plate). In this article, the estimation of accurate RC parameters from the FEA thermal model is demonstrated in COMSOL. The electrical model having temperature-dependent power loss model is coupled to a refined thermal model and solved in a circuit simulator, PLECS. The proposed method is applied in two applications: assessing thermal interaction between IGBTs and antiparallel diodes in a half-bridge power module and assessing thermal interaction among the discrete switches in an interleaved bidirectional dc–dc converter. Results show that the impact of material nonlinearity, thermal grease layer, and cooling boundary conditions are significant for accurate prediction of IGBT and diode temperatures. The proposed model is consistent with FEA results and differs by 2%–6.5% compared with the experimental results. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
8. Mitigation of Gap Losses in Nanocrystalline Tape-Wound Cores.
- Author
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Calderon-Lopez, Gerardo, Wang, Yiren, and Forsyth, Andrew J.
- Subjects
FINITE element method ,ADHESIVE tape ,POWER electronics ,POWER density - Abstract
A split-core technique is proposed to mitigate the gap losses in high-frequency nanocrystalline cores, which enables significant size reductions in thermally limited designs. Finite element analysis is used to examine the gap loss dependence on core width D revealing a nonlinear relationship of the form loss ∝ $D^{\alpha }$. α is approximately constant for frequencies of 10–200 kHz over the range of core widths typically used in power electronics, but α increases with gap length. Splitting the core into a number of subcores can therefore provide significant reductions in gap loss, especially with larger gap lengths. The results from a 300-A (peak), 200-A (continuous) inductor show that with three subcores and a gap length of 4 mm, the gap losses are reduced by 50%, and the hot-spot temperature is reduced by 24.5 °C. Using the technique it is estimated that the original inductor weight could be reduced by 40% with four split cores, making a significant impact on converter power density. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
9. A Design Optimization Tool for Maximizing the Power Density of 3-Phase DC?AC Converters Using Silicon Carbide (SiC) Devices.
- Author
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Laird, Ian, Yuan, Xibo, Scoltock, James, and Forsyth, Andrew J.
- Subjects
POWER density ,SILICON carbide ,DC-AC converters ,PROCESS optimization ,POWER tools ,PASSIVE components ,ELECTROMAGNETIC interference - Abstract
The emergence of wide-bandgap devices, e.g., silicon carbide (SiC), has the potential to enable very high-density power converter design with high-switching frequency operation capability. A comprehensive design tool with a holistic design approach is critical to maximize the overall system power density, e.g, by identifying the optimal switching frequency. This paper presents a system level design tool that optimizes the power density (volume or mass) of a three-phase, two-level dc–ac converter. The design tool optimizes the selection of the devices, heatsink and passive components (including the design of the line, electromagnetic interference (EMI), and dc-link filters) to maximize the power density. The structure of the optimization algorithm has been organized to reduce the number of potential design combinations by over 99%, and thus, produces fast simulation times. The design tool predicts that when SiC devices are used instead of Si ones, the power density is increased by 159.4%. A 5 kW, 600-V dc-link, three-phase, two-level dc–ac converter was experimentally evaluated in order to confirm the accuracy of the design tool. [ABSTRACT FROM PUBLISHER]
- Published
- 2018
- Full Text
- View/download PDF
10. All-GaN-Integrated Cascode Heterojunction Field Effect Transistors.
- Author
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Jiang, Sheng, Lee, Kean Boon, Guiney, Ivor, Miaja, Pablo F., Zaidi, Zaffar H., Qian, Hongtu, Wallis, David J., Forsyth, Andrew J., Humphreys, Colin J., and Houston, Peter A.
- Subjects
ELECTRIC properties of gallium nitride ,CASCADE converters ,HETEROJUNCTION field effect transistors ,ELECTRIC switchgear ,METAL oxide semiconductor field-effect transistors - Abstract
All-GaN-integrated cascode heterojunction field effect transistors were designed and fabricated for power switching applications. A threshold voltage of +2 V was achieved using a fluorine treatment and a metal–insulator–semiconductor gate structure on the enhancement mode part. The cascode device exhibited an output current of 300 mA/mm by matching the current drivability of both enhancement and depletion mode parts. The optimization was achieved by shifting the threshold voltage of the depletion mode section to a more negative value with the addition of a dielectric layer under the gate. The switching performance of the cascode was compared to the equivalent GaN enhancement-mode-only device by measuring the hard switching speed at 200 V under an inductive load in a double pulse tester. For the first time, we demonstrate the switching speed advantage of the cascode over equivalent GaN enhancement-mode-only devices, due to the reduced Miller-effect and the unique switching mechanisms. These observations suggest that practical power switches at high power and high switching frequency will benefit as part of an integrated cascode configuration. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
11. High-Frequency Gap Losses in Nanocrystalline Cores.
- Author
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Wang, Yiren, Calderon-Lopez, Gerardo, and Forsyth, Andrew J.
- Subjects
NANOCRYSTALS ,ELECTRIC inductors ,FINITE element method ,ELECTRIC windings ,POWER electronics - Abstract
Finite element analysis is used to examine the gap losses that occur in finely laminated nanocrystalline inductor cores under high-frequency operation. The losses are seen to be concentrated in the region of the air gap and the dependence of the losses on key design parameters and operating conditions is explored. The results show that gap losses can be significant in this type of core, creating hot spots around the gap, and the losses are not accurately predicted by established design equations for low-frequency laminated cores. A modified loss equation is proposed. Validation is provided by measurements on a 300-A, 60 kHz inductor. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
12. Enhanced Average-Value Modeling of Interleaved DC?DC Converters Using Sampler Decomposition.
- Author
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Villarruel-Parra, Alejandro and Forsyth, Andrew J.
- Subjects
- *
CONVERTERS (Electronics) , *PREDICTION models , *TRANSFER functions , *NUCLEAR counters , *SWITCHING circuits - Abstract
To provide a basis for controller design in interleaved dc–dc converters, an improved small-signal averaged model is presented. Sampler decomposition techniques are used to represent the interleaved operation of the individual control loops within the converter. The resultant model reveals interaction effects and instability phenomena that are not predicted by a simple noninterleaved model, and which impose significant restrictions on the selection of control parameters. The model is validated by detailed simulations and experimental results from a digitally controlled dual-interleaved boost converter. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
13. Evaluation of SiC BJTs for High-Power DC–DC Converters.
- Author
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Calderon-Lopez, Gerardo, Forsyth, Andrew J., Gordon, David L., and McIntosh, Jim R.
- Subjects
- *
DC-to-DC converters , *SILICON carbide , *POWER electronics , *BIPOLAR transistors , *ELECTRIC vehicles , *POWER semiconductors - Abstract
The design of a 200-A, all-SiC power-module-based on bipolar junction transistor devices is described, and the impact of the module is assessed on the performance of a 50-kW dc-dc converter for electric vehicle applications, particularly the overall weight and efficiency. Using a hard-switching dual-interleaved topology, which has proven high efficiency and high-power density capability, the operation of a 50-kW, 75-kHz all-SiC converter is compared with that of an insulated-gate bipolar transistor-based silicon converter, switching at 25 kHz, each providing 600-V output. The results show that the total losses are reduced by almost 40%, whilst the overall weight is reduced by 27%, achieving a power density of 10.5 kW/kg. Experimental results of the SiC converter operating at 220-600 V, 52.8 kW are provided, showing an efficiency of 97%. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
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