Mutsuo Nakaoka

Bio: Mutsuo Nakaoka is an academic researcher from Kyungnam University. The author has contributed to research in topics: Pulse-width modulation & Inverter. The author has an hindex of 36, co-authored 766 publications receiving 6670 citations. Previous affiliations of Mutsuo Nakaoka include Yamaguchi University & Kobe University.

Induction-heated cooking appliance using new quasi-resonant ZVS-PWM inverter with power factor correction

Abstract: This paper presents a new prototype of a voltage-fed quasi-load resonant inverter with a constant-frequency variable-power (CFVP) regulation scheme, which is developed for the next-generation high-frequency high-power induction-heated (IH) cooking appliances in household applications. This application-specific high-frequency single-ended push-pull inverter using new-generation specially designed insulated gate bipolar transistors (IGBTs) can efficiently operate under a principle of zero-voltage switching pulsewidth modulation (ZVS-PWM) strategy. This low-cost soft-switching inverter using reverse-conducting and reverse-blocking IGBTs is more suitable for multiple-burner-type induction-heating cooking appliances. The operating principle and unique features of a new resonant ZVS-PWM inverter circuit topology is originally described, together with its steady-state power regulation characteristics, which are illustrated on the basis of its computer-aided simulation and experimental results. The ZVS operation condition on power regulation, loss analysis of new IGBTs incorporated into this inverter, and its active filtering performance are discussed for IH cooking appliances.

A novel pulse-density-modulated high-frequency inverter for silent-discharge-type ozonizer

Abstract: This paper presents a novel prototype of a voltage-source load resonant inverter using insulated gate bipolar transistors for driving a silent-discharge-type ozone-generation tube. Ozone-generation technology has a history of more than 100 years and ozonization has been recognized as one of the best methods for water treatment, desinfection, industrial wastes utilization, and so on. However, some technological difficulties related to efficient ozone production and high cost of the ozone-generating equipment have been significant problems restricting ozone usage in the industrial plants. Introduced in this paper is a pulse-density-modulated high-frequency inverter for a silent-discharge-type ozonizer, which is developed with the aim to improve power conversion and control characteristics of the ozone generation by using advances in power electronic technology. The developed system implements the feedforward control-based pulse-density-modulation control scheme with pulsewidth-modulation feedback control strategy to compensate temperature and other environmental influences on ozone gas output.

Commercial Frequency AC to High Frequency AC Converter With Boost-Active Clamp Bridge Single Stage ZVS-PWM Inverter

Abstract: This paper presents a novel soft-switching pulsewidth modulation (PWM) utility frequency ac to high frequency (HF) ac power conversion circuit incorporating boost-active clamp single stage inverter topology. This power converter is more suitable and acceptable for cost effective HF consumer induction heating applications. Its operating principle is presented using the switching mode equivalent circuits in addition to the operating voltage and current waveforms. The operating performances of this high frequency inverter using the latest insulated gate bipolar transistors are illustrated, which includes HFAC power regulation ranges and actual efficiency characteristics based on zero voltage soft switching operation ranges and the power dissipation loss analysis as compared with those of the previously developed high frequency inverter. In addition, a dual mode selected control scheme of this high frequency inverter based on a constant frequency asymmetrical PWM and pulse density modulation control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The practical effectiveness of this power frequency converter is substantially proved on the basis of experimental results from practical design example.

Time-sharing boost chopper cascaded dual mode single-phase sinewave inverter for solar photovoltaic power generation system

Abstract: This paper presents a novel prototype circuit topology and control scheme of a high efficiency time-sharing dual mode single-phase sinewave PWM inverter for small scale solar PV power generation system, which is composed of partially controlled sinewave absolute PWM boost chopper in the first power processing stage as well as partially controlled sinewave PWM inverter in the second power processing stage. Its unique operating principle of two power processing stage with time-sharing dual mode sinewave modulation strategy is described in addition to a design example. Finally, this new conceptual single-phase sinewave PWM inverter related to solar PV power generation system suitable for residential application is evaluated and discussed on the basis of computer simulation and experimental results. The effectiveness of proposed inverter is proved from a practical point of view.

Cost effective phase shifted pulse modulation soft switching high frequency inverter for induction heating applications

Abstract: A cost-effective high-efficiency high-frequency inverter with a PSM (phase-shifted pulse modulation) scheme is proposed for medium power (5–30 kW) induction heating applications. This inverter topology can achieve soft switching commutation in a wide range of power regulation, without an auxiliary active resonant snubber circuit. The high-frequency PSM control scheme presented can provide not only effective power regulation of the proposed inverter using IGBTs, but also soft switching commutation. Theoretical equations for the soft switching operation region are derived from the practical consideration of the gate pulse control strategy, in which the soft switching operation is limited only by the duration of dead time. Through experimental comparison of switching losses in the two-in-one IGBT power module, consideration is given to how much the effect of soft switching can improve actual efficiency. In this discussion, the cost effective high-efficiency inverter circuit topology is realised. The proposed inverter accomplishes soft switching operation over a wide power regulation range. The actual power conversion efficiency reached was 96.7%.

A review of single-phase improved power quality AC-DC converters

Abstract: Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input AC mains and precisely regulated DC output in buck, boost, buck-boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode AC-DC converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference.

Design considerations for a contactless electric vehicle battery charger

Abstract: This paper overviews theoretical and practical design issues related to inductive power transfer systems and verifies the developed theory using a practical electric vehicle battery charger. The design focuses on the necessary approaches to ensure power transfer over the complete operating range of the system. As such, a new approach to the design of the primary resonant circuit is proposed, whereby deviations from design expectations due to phase or frequency shift are minimized. Of particular interest are systems that are neither loosely nor tightly coupled. The developed solution depends on the selected primary and secondary resonant topologies, the magnetic coupling coefficient, and the secondary quality factor.

Step-Up DC–DC Converters: A Comprehensive Review of Voltage-Boosting Techniques, Topologies, and Applications

Abstract: DC–DC converters with voltage boost capability are widely used in a large number of power conversion applications, from fraction-of-volt to tens of thousands of volts at power levels from milliwatts to megawatts. The literature has reported on various voltage-boosting techniques, in which fundamental energy storing elements (inductors and capacitors) and/or transformers in conjunction with switch(es) and diode(s) are utilized in the circuit. These techniques include switched capacitor (charge pump), voltage multiplier, switched inductor/voltage lift, magnetic coupling, and multistage/-level, and each has its own merits and demerits depending on application, in terms of cost, complexity, power density, reliability, and efficiency. To meet the growing demand for such applications, new power converter topologies that use the above voltage-boosting techniques, as well as some active and passive components, are continuously being proposed. The permutations and combinations of the various voltage-boosting techniques with additional components in a circuit allow for numerous new topologies and configurations, which are often confusing and difficult to follow. Therefore, to present a clear picture on the general law and framework of the development of next-generation step-up dc–dc converters, this paper aims to comprehensively review and classify various step-up dc–dc converters based on their characteristics and voltage-boosting techniques. In addition, the advantages and disadvantages of these voltage-boosting techniques and associated converters are discussed in detail. Finally, broad applications of dc–dc converters are presented and summarized with comparative study of different voltage-boosting techniques.

Review of Nonisolated High-Step-Up DC/DC Converters in Photovoltaic Grid-Connected Applications

Abstract: The photovoltaic (PV) grid-connected power system in the residential applications is becoming a fast growing segment in the PV market due to the shortage of the fossil fuel energy and the great environmental pollution. A new research trend in the residential generation system is to employ the PV parallel-connected configuration rather than the series-connected configuration to satisfy the safety requirements and to make full use of the PV generated power. How to achieve high-step-up, low-cost, and high-efficiency dc/dc conversion is the major consideration due to the low PV output voltage with the parallel-connected structure. The limitations of the conventional boost converters in these applications are analyzed. Then, most of the topologies with high-step-up, low-cost, and high-efficiency performance are covered and classified into several categories. The advantages and disadvantages of these converters are discussed. Furthermore, a general conceptual circuit for high-step-up, low-cost, and high-efficiency dc/dc conversion is proposed to derive the next-generation topologies for the PV grid-connected power system. Finally, the major challenges of high-step-up, low-cost, and high-efficiency dc/dc converters are summarized. This paper would like to make a clear picture on the general law and framework for the next-generation nonisolated high-step-up dc/dc converters.

Inductive power transfer

Abstract: A detection method for use in a primary unit of an inductive power transfer system, the primary unit being operable to transmit power wirelessly by electromagnetic induction to at least one secondary unit of the system located in proximity to the primary unit and/or to a foreign object located in said proximity, the method comprising: driving the primary unit so that in a driven state the magnitude of an electrical drive signal supplied to one or more primary coils of the primary unit changes from a first value to a second value; assessing the effect of such driving on an electrical characteristic of the primary unit; and detecting in dependence upon the assessed effect the presence of a said secondary unit and/or a foreign object located in proximity to said primary unit.