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Your search keyword '"Akagi, Hirofumi"' showing total 88 results
Start Over Author "Akagi, Hirofumi" Publisher institute of electrical and electronics engineers (ieee)
88 results on '"Akagi, Hirofumi"'

5. A Medium-Voltage Large Wind Turbine Generation System Using an AC/AC Modular Multilevel Cascade Converter

Author

THITICHAIWORAKORN, N, THITICHAIWORAKORN, NUNTAWAT, Hagiwara, Makoto, and Akagi, Hirofumi

Subjects
Engineering, business.industry, 020209 energy, 020208 electrical & electronic engineering, Electrical engineering, Energy Engineering and Power Technology, 02 engineering and technology, Permanent magnet synchronous generator, Voltage regulator, AC power, Voltage optimisation, AC/AC converter, Cascade converter, 0202 electrical engineering, electronic engineering, information engineering, Electronic engineering, Power semiconductor device, Electrical and Electronic Engineering, business, Voltage
Abstract

The generator voltage of a cutting-edge wind turbine generation system (WTGS) is expected to increase from the conventional low-voltage level of 690 V to a medium-voltage level of 6.6 kV with a power level up to 10 MW without the application of a parallel connection of multiple power units. On the other hand, it is difficult to use a conventional two-level or three-level converter in a WTGS with a dc-link voltage of 10–13 kV owing to the limitations on the voltage ratings of power devices. This paper presents a 10-MW WTGS consisting of a three-phase open-winding synchronous generator equipped with six lead terminals and a modular multilevel cascade converter (MMCC) formed by three identical subconverters. The MMCC carries out direct ac/ac power conversion from three single-phase voltages with a time-varying frequency (from the generator) to a three-phase voltage with a line frequency of 50 Hz. This paper discusses the operating principles and control methods for the WTGS, followed by simulations using the software package PSCAD/EMTDC. The experimental result obtained from a 200 V 6-kW downscaled system confirms the reliability of simulation results of the complete three-phase system.

Published
2016

6. Theory and Experiment on an Optimal Carrier Frequency of a Modular Multilevel Cascade Converter With Phase-Shifted PWM

Author

SASONGKO, FIRMAN, Sasongko, Firman, Sekiguchi, Kei, Oguma, Kouta, Hagiwara, Makoto, and Akagi, Hirofumi

Subjects
Engineering, business.industry, 020209 energy, 020208 electrical & electronic engineering, 02 engineering and technology, Converters, Modular design, Harmonic analysis, Cascade converter, Cascade, Modulation, Control theory, 0202 electrical engineering, electronic engineering, information engineering, Transient (oscillation), Electrical and Electronic Engineering, business, Pulse-width modulation
Abstract

This paper provides theoretical and experimental discussions on an optimal carrier frequency for a phase-shifted pulsewidth modulation modular multilevel cascade converter for grid connections. The theoretical discussion concludes that a ratio of the optimal carrier frequency with respect to the supply (ac) frequency is 5/2. A three-phase downscaled front-to-front system is designed, constructed, and tested to confirm validity of the theoretical discussion. It consists of a pair of three-phase modular multilevel cascade converters rated at 400 Vdc and 10 kW, where the carrier frequency is set to 450 Hz and the ac frequency to 180 Hz, that is, their ratio is equal to 5/2. Moreover, simulated waveforms are compared to experimental ones under the same operating conditions. Both experimental and simulated waveforms agree well with each other not only in steady states but also in transient states.

Published
2016

10. A Grid-Level High-Power BTB (Back-To-Back) System Using Modular Multilevel Cascade Converters WithoutCommon DC-Link Capacitor

Author

Sekiguchi, Kei, KHAMPHAKDI, PRACHA, Hagiwara, Makoto, and Akagi, Hirofumi

Subjects
Computer science, Converters, Inductor, Industrial and Manufacturing Engineering, law.invention, Chopper, Capacitor, Control and Systems Engineering, law, Electronic engineering, Transient (oscillation), Electrical and Electronic Engineering, Low voltage, Pulse-width modulation, Voltage
Abstract

This paper provides an intensive discussion on analysis, simulation, and experiment of a back-to-back (BTB) system unifying two modular multilevel cascade converters based on double-star chopper cells (MMCCs-DSCCs). Each of the two DSCCs connected back-to-back consists of multiple cascaded chopper cells and a center-tapped inductor per leg. Low voltage steps bring significant reductions in harmonic voltage and current to the BTB system. Neither dc-link capacitor nor voltage sensor is required for regulating the dc-link voltage and controlling the dc-link current. A three-phase 200-V, 10-kW, 50-Hz downscaled BTB system with phase-shifted PWM is designed, constructed, and tested to verify its operating principles and performance. Analytical, simulated, and experimental results agree well with each other in steady and transient states. Experimental waveforms confirm the effectiveness of a self-starting/restarting procedure.

Published
2014

30. Pulse-density-modulated power control of a 4 kW, 450 kHz voltage-source inverter for induction melting applications

Author

Fujita, Hideaki, Akagi, Hirofumi, Sano, K., and Leonard, R. H.

Subjects
Engineering, melting, Induction heating, business.industry, Electrical engineering, Induction furnace, DC-AC power convertors, pulse modulation, induction heating, power control, Industrial and Manufacturing Engineering, resonant power convertors, Control and Systems Engineering, Modulation, Electronic engineering, Inverter, RLC circuit, Electrical and Electronic Engineering, business, Pulse-density modulation, Pulse-width modulation, Power control
Abstract

This paper presents a 4 kW, 450 kHz voltage-source inverter with a series resonant circuit for induction melting applications, which is characterized by the power control based on pulse density modulation (PDM). The pulse-density-modulated inverter makes an induction melting system simple and compact, thus leading to higher efficiency. A modulation strategy is proposed to realize the induction melting system capable of operation at the frequency and power level of interest. Some interesting experimental results are shown to verify the validity of the concept

Published
1996

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