担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Condition monitoring plays an important role in improving reliability of power electronic converters including their dc-link capacitors because it contributes to predicting converter failures. This paper proposes a current-sensor-less con-dition monitoring method of a dc-link capacitor used in a three-phase PWM inverter with a front-end six-pulse diode rectifier and a dc inductor. The method measures both the capacitance and equivalent-series resistance (ESR) of the capacitor without any current sensor. Theoretical analysis reveals that the capacitor current is calculated by the three-phase ac source voltage and the dc inductor. Experimental results obtained from a 200-V laboratory system confirmed that both the ESR and capacitance changes were observed without any current sensors.

DOI： 10.23919/IPEC-Himeji2022-ECCE53331.2022.9807247

Scopus

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The shoot-through fault in inverters results from a gate noise voltage of power semiconductor switches including IGBTs. Testing the gate voltage under the high-speed switching event is important to evaluate immunity to the fault as well as to analyze the mechanism of the fault. This paper presents a testing method of shoot-through immunity in a PWM inverter consisting of IGBTs because the conventional double-pulse test can miss the shoot-through fault in the inverter. Theoretical analysis reveals that the N-base charge has influence on the gate-emitter voltage in the IGBT, which disturbs evaluating the shoot-through immunity in the inverter. This implies that IGBTs have a different characteristic from MOSFETs when the double-pulse test is carried out. The testing method introduces an additional pulse into the off-state IGBT to release the N-base charge, the circuit operation of which is the same as the inverter. Experimental results confirmed that the method did not affected by the N-base voltage, so that it is applicable to testing the shoot-through immunity of IGBTs in an inverter.

DOI： 10.1016/j.microrel.2021.114289

Scopus

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担当区分：筆頭著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）

<p>1．はじめに</p><p>アルミニウム電解コンデンサ（以下，Al電解コンデンサ）は安価・大容量という特長を有し，小容量のスイッチング電源から低圧のインバータまで広く利用されている^（1）。他の種類のコンデンサに比べ低寿命で損失も大きいと指摘されることがあるが，近年の技術開発によりこれら</p>

DOI： 10.1541/ieejjournal.141.630

CiNii Article

CiNii Research

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Attention has been paid to the next-generation IGBT toward CMOS compatible wafer processes, which can be driven by a 5-V logic level due to its low threshold gate voltage. This low threshold voltage makes the so-called shoot-through fault severer. Even though the switching speed of the IGBT is intentionally reduced, the shoot-through fault can happen. This paper presents shoot-through protection for an inverter consisting of the next-generation IGBTs with gate impedance reduction. Theoretical analysis reveals the criterion of the gate impedance with taking parasitic parameters of the inverter into account.

DOI： 10.1016/j.microrel.2020.113765

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2019 IEEE. Inverters used in motor-drive and grid-connected applications usually employ current sensors at the output terminal because they have to control the output current. Existing current sensors like the Hall sensor and the current transformer are a constraint to reduce the volume and cost of the inverter. This paper proposes an output-current measurement method of a PWM inverter using a tiny PCB sensor that is based on the so-called Rogowski coil and can be integrated into an IGBT module. The method utilizes the switching current of the low-side switch for reproducing the output current, which allows using the PCB sensor because the switching current consists of high-frequency components. The method uses a single PCB sensor per leg and takes the polarity of the output current into account. Experimental results using a half-bridge sinusoidal PWM inverter verify that the proposed method measures the output current including its fundamental frequency component, switching ripple one, and polarity.

DOI： 10.1109/ECCE.2019.8912662

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2019 IEEE. This paper proposes a practical current sensor integration in the intelligent power modules (IPMs) using simple PCB Rogowski coil sensors. The PCB sensors produce signals that proportional to the high frequency switching current from high and low side IGBTs. Then with only general-purpose Op-Amps and photo-couplers based integrator and sample and hold (S/H) circuits reproduce output current of the inverter. Specifically, the "envelop tracking" method has successfully proved on an experimental inverter setup. A significant accomplishment of an improved new analog circuit is the measurement during narrow pulse width around unity modulation index that leads to higher inverter output power.

DOI： 10.1109/ISPSD.2019.8757580

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2019 IEEE. Parasitic inductances in power semiconductor packages affect the device switching speeds. The self-inductance of the source terminal has been considered to be the main factor that limits the switching speed, but mutual inductances among the three terminals also influence the speed. This paper proposes a method to measure the source self-inductance and the mutual inductances in the package using time-domain reflectometry (TDR) and time-domain transmissometry (TDT) that reveals the limitation of the switching speed. The measurement results agreed well with those of Q3D simulation.

DOI： 10.1109/ISPSD.2019.8757658

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2019 IEEE. Negative biasing of the gate voltage in a scaled insulated gate bipolar transistor (IGBT) during the off-state was modeled and found to be effective against self-turn-on failures. The required self-turn-on-free criteria were verified experimentally.

DOI： 10.1109/ISPSD.2019.8757665

Scopus

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>This paper presents a condition-monitoring method of dc-link capacitors used in a high-power three-phase PWM inverter with an evaluation circuit intended for ageing tests. Although its power rating is 1/25 of the inverter, the evaluation circuit provides the equivalent ripple current waveform and dc-bias voltage to the high-power inverter. The monitoring method independently extracts the capacitance and ESR of the dc-link capacitor, where the fast Fourier transform is introduced to the ripple current waveform and the dc-link voltage of the evaluation circuit. Experimental results verify that the monitoring method obtains both the ESR and capacitance changes of a capacitor under test.</p>

DOI： 10.1541/ieejjia.8.480

Scopus

CiNii Article

CiNii Research

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2018 IEEE. This paper proposes a calorimetric power-loss measurement method suitable for a high-power film capacitor used in the dc link of a high-power three-phase PWM inverter. The measurement method is characterized by using a thermally-insulated container and an evaluation circuit for dc-link capacitors. Introduction of the thermally-insulated container achieves an accurate power loss measurement that is of the order of 1 W. The evaluation circuit provides the equivalent ripple current waveform and dc-bias voltage to those of the high-power three-phase PWM inverter although its power rating is 1/24 of the high-power inverter. This combination makes it possible to measure the power loss of the capacitor under actual voltage/current condition at low cost. Experimental results obtained from a 1200-V 210-kVA system verify the viability and effectiveness of the proposed method.

DOI： 10.1109/ECCE.2018.8557709

Scopus

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2018 IEEJ Industry Application Society. This paper presents a condition monitoring method of dc-link capacitors used in a high-power three-phase PWM inverter intended for load life testing with an evaluation circuit consisting a low-voltage inverter. The evaluation circuit provides the equivalent ripple current waveform and dc-bias voltage to those of the high-power inverter. Hence, the monitoring method allows the load life testing with the equivalent condition to the high-power inverter at low cost. Experimental results verify that the monitoring method extracts both the ESR and capacitance changes of a capacitor under test.

DOI： 10.23919/IPEC.2018.8507885

Scopus

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Elsevier Ltd Condition monitoring plays an important role in estimating health condition of capacitors because the ageing of the capacitors is usually accompanied by an increase in equivalent series resistance (ESR) and a decrease in capacitance. Either capacitance or ESR cannot be a unique indicator of the lifetime of capacitors in some cases. This paper presents a condition monitoring method of a dc-link capacitor used in a three-phase PWM inverter with a front-end diode rectifier intended for motor drives. The monitoring method extracts both the ESR and capacitance of a capacitor under test from the actual ripple current and voltage without disconnecting the capacitor nor injecting an additional current. The monitoring method, therefore, can be implemented online. Experimental results verify that the monitoring method independently obtains the ESR and capacitance changes of the capacitor under test. This contributes to accurate lifetime estimation of dc-link capacitors.

DOI： 10.1016/j.microrel.2018.07.023

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Elsevier Ltd In this paper, we propose the criteria of bias voltage from parasitic capacitance and demonstrate the criteria in an experiment with the present IGBT. The bias voltage criteria are theoretically predicted for the new generation IGBT based on the scaling principle. For safe switching, the required gate voltage bias is predicted to be −1.2 V or less for the present IGBTs and − 6 V or less is required to completely cancel the gate noise voltage. From the IGBT design, the bias voltage of scaling IGBT requires −2 V to completely cancel the gate noise voltage.

DOI： 10.1016/j.microrel.2018.06.026

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Elsevier Ltd Health monitoring of the power conversion system is very important. Therefore, we developed a new method for measuring IGBT currents and reproducing average load current to monitor IGBTs. This method was successfully tested on an experimental setup which showed that the tiny PCB sensors can be integrated into intelligent power modules. We proposed an inexpensive analogue circuit which is suitable for capturing current information from a tiny PCB Rogowski coil. The sensors and corresponding circuit can be embedded into an Intelligent Power Module. The method was named “Envelop tracking” as it simultaneously measures the currents of the high and low side switches of a power converter and reproduces the upper and lower edges of the load current which can be averaged by further digital processing.

DOI： 10.1016/j.microrel.2018.06.028

Scopus

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Elsevier Ltd Attention has been paid to reliability-related issues for dc-link capacitors such as monitoring methods, power-loss estimation, and ageing tests. The degradation of the capacitors depends on their operating condition including temperature, ripple current, and dc-bias voltage, which has a strong influence on failures as well. In design stages of power converters, it is desirable to know the relation between the degradation and electrolytic parameters. This paper makes an intensive discussion on the voltage dependence of the degradation of a small aluminum electrolytic capacitor with an ageing test and a leakage-current measurement. The ageing test reveals that a higher dc-bias voltage brings a faster increase in ESR but results in a slower drop in capacitance in a range within the rated voltage. This result implies that either capacitance or ESR cannot be a unique indicator of the lifetime. Attention should be paid both to the ESR and to the capacitance when one monitors the capacitor condition. On the other hand, more than the rated voltage leads a rapid degradation of the capacitor, which can be confirmed by a leakage-current measurement instead of the ageing test.

DOI： 10.1016/j.microrel.2018.02.012

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017 Elsevier Ltd The shoot-through phenomenon has not been fully discussed for high-power inverters with IGBTs. This is because a negative gate voltage is applied to IGBTs during off states. Recently, attention is paid to an improved gate driver with only a positive gate voltage in order to meet demands for simplification, integration, and reduction in power consumption as well as in cost of the gate driver. Moreover, the threshold voltage of the next-generation IGBT will decrease with microfabrication techniques of the gate structure. This will make the shoot-through phenomenon severer and degrade the inverter reliability with the next-generation IGBTs. The influence of the parasitic parameters in both the IGBT and circuit on the shoot-through mechanism has not been investigated so far. This paper clarifies the shoot-through mechanism and investigates the impact of the next generation IGBTs on the inverter reliability. The influence of the internal capacitance of IGBT including stray inductance on inverter reliability is experimentally confirmed.

DOI： 10.1016/j.microrel.2017.06.087

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017 Elsevier Ltd High reliability is required for power modules because they are increasingly demanded as key devices in an energy-saving society. However, commercially available current sensors like current transformers and Rogowski coils are still of large size. Therefore, it is impossible to measure the current in small parts. In addition, long wiring with large sensors reduces the performance of power modules. In previous studies, we proposed a current sensor of PCB Rogowski coil with a fishbone pattern. The sensor is sufficiently small and thin with high accuracy for power module application. The PCB current sensor can be used as a built-in current sensor in power modules from the viewpoint of size. However, the sensor requires further improvement to be attached to bonding wire from a usability perspective. We propose a new pattern for the clamp-type PCB sensor and fabricate the PCB sensor as a built-in sensor in a power module. With the new pattern, it is possible to move and widen the gap for clamping. The signal error is small even though the sensor is inclinedly attached to the bonding wire. The accuracy is confirmed by a comparison between the clamp-type PCB sensor in the module and a commercially available current sensor outside the module. The clamp-type PCB sensor can be applied for intelligent power modules as well as current measurement for power electronic converters.

DOI： 10.1016/j.microrel.2017.06.026

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 1986-2012 IEEE. This paper proposes a new output current measuring method using tiny printed-circuit-board (PCB) current sensors. The method will make it possible to install the PCB current sensors in an insulated-gate bipolar transistor (IGBT) module. The PCB sensor picks up a switching current flowing through an IGBT chip, and then a combination of a digital circuit based on field-programmable gate array and an integrator circuit reproduces the output current of an inverter from the switching current. A proof-of-concept experimental verification is carried out using a buck converter, which verifies that the proposed method detects a dc component of the output current as well as a ripple component although the PCB sensor is based on the so-called Rogowski coil.

DOI： 10.1109/TPEL.2016.2606111

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2017 IEEJ. This paper proposes a new power module concept that integrates output current measurement function to make inverters compact. The current measurement function is realized by tiny printed-circuit-board (PCB) Rogowski coils. The PCB Rogowski coil picks up a switching current flowing through an IGBT chip, and then a combination of a digital circuit based on a field-programmable-gate-array (FPGA) and an integrator circuit reproduces the output current of the inverter from the switching current. A major concern of the new power module is the effect of reverse recovery current of free-wheeling diodes because the reverse recovery current is superimposed on the switching current. This paper proposes a mitigating method of the reverse recovery current.

DOI： 10.23919/ISPSD.2017.7988911

Scopus

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© VDE VERLAG GMBH · Berlin · Offenbach. High-power conversion systems are based not only on three-phase inverters but also on singlephase inverters because modular multilevel cascade converters (MMCC) consist of half- or fullbridge single-phase converters. Their DC-link capacitors are a major constraint on the improvement of power density as well as of reliability. Evaluation of dc-link capacitors in terms of power loss, ageing, and failure rate will play an important role in the next-generation power converters. This paper presents an evaluation circuit for dc-link capacitors used in a high-power single-phase PWM inverter. The evaluation circuit produces a practical ripple current waveform and a dc bias voltage into a capacitor under test with a downscaled voltage-rating inverter, which is equivalent to those of the full-scale inverter. Theoretical analysis and experimental results verify the effectiveness of the evaluation circuit.

DOI： 10.1109/SBMicro.2017.7990846

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2016 Elsevier Ltd DC-link capacitors are a major factor of degrading reliability of power electric converters because they usually have a shorter lifetime and higher failure rate than those of semiconductor devices or magnetic devices. Characteristics of the capacitors are usually evaluated by a single sinusoidal current waveform. However, actual current flowing out of the converter into the capacitor is a modulated square current waveform. This paper provides experimental comparison of the power loss dissipated in an aluminum electrolytic capacitor between sinusoidal and square-wave current injections. Power loss is estimated by temperature rise of the capacitor. Experimental results confirm that power losses of the square-wave current injection were always lower than those of the sinusoidal current injection by 10–20%. Moreover, the power losses of the square-wave current injection can be estimated by a synthesis of fundamental and harmonic currents based on the Fourier series expansion, which brings a high accuracy less than 1% when more than fifth harmonic current is introduced. This comparison will be useful for estimating power loss and life time of electrolytic capacitors.

DOI： 10.1016/j.microrel.2016.07.049

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2016 IEEE. Stray inductance inside power device package will be a constraint on improvement of power density as well as switching frequency in power converters because the converters will suffer from electromagnetic interference (EMI)-related problems. This paper proposes a measurement method of mutual inductance for power device packages using time domain reflectometry. The method is characterized by introducing four-terminal measurement that distinguishes self and mutual inductances among collector, emitter, and gate terminals. A measurement fixture for a discrete IGBT is designed, constructed, and tested to ensure repeatability of the proposed method. Experimental results verifies the viability of the proposed method.

DOI： 10.1109/ECCE.2016.7855285

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

This paper presents a five-level diode-clamped pulse width-modulated (PWM) inverter intended for a medium-voltage motor drive with a constant-torque load but no regenerative braking. It is applicable to drilling rigs, extruders, and rubber mixers. The power conversion system consists of a three-phase six-pulse diode rectifier, a five-level diode-clamped PWM inverter, and a dc-voltage-balancing circuit including a single coupled inductor. The five-level inverter is characterized by injecting a common ninth-harmonic zero-sequence voltage on each of the three-phase reference voltages in a low-modulation-index region. This injection contributes not only to mitigating magnetic-flux fluctuation of the coupled inductor but also to making uniform the power losses produced by eight insulated-gate bipolar transistor modules per leg. In addition, the dc-voltage-balancing circuit introduces a control method capable of reducing an amplitude of magnetic flux of the coupled inductor. The combination of this control method and the ninth-harmonic zero-sequence voltage injection keeps the peak value of the magnetic flux within its designed value. © 2012 IEEE.

DOI： 10.1109/TPEL.2012.2185068

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

This paper focuses on a medium-voltage motor drive requiring no regenerative braking. It is operated not only in a high-speed region but also in a low-speed region with the rated torque, intended for an application to drilling rigs. The power conversion system consists of a front-end diode rectifier, a five-level diode-clamped PWM inverter, and a dc-voltage-balancing circuit including a single coupled inductor. The five-level diode-clamped inverter is characterized by injecting a common ninth-harmonic zero-sequence voltage on each of the three-phase reference voltages for mitigating magnetic-flux fluctuation of the coupled inductor of the dc-voltage-balancing circuit. Moreover, the voltage injection can make the power-loss distribution of eight insulated gate bipolar transistors (IGBTs) per leg close to an even profile. Experimental results obtained from a 200-V 5.5-kW downscaled model confirm the viability and effectiveness of the power conversion system, indicating that the ninth-harmonic zero-sequence voltage injection mitigates the magnetic-flux fluctuation. © 2011 IEEE.

DOI： 10.1109/ICPE.2011.5944415

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記述言語：英語   掲載種別：研究論文（学術雑誌）

This paper proposes a new dc-voltage-balancing circuit for a five-level diode-clamped inverter intended for a medium-voltage motor drive with a three-phase diode rectifier used as the front end. This circuit consists of two unidirectional choppers and a single coupled inductor with two galvanically isolated windings. The inductor produces no net dc magnetic flux because the individual dc magnetic fluxes generated by the two windings are canceled out with each other. This makes the inductor compact by a factor of six, compared with the balancing circuit including two noncoupled inductors. Moreover, introducing phase-shift control to the new balancing circuit makes it possible to adjust the midpoint voltage. As a result, the dc mean voltages of all the four split dc capacitors can be balanced, independent of inverter control. Experimental results obtained from a 200-V 5.5-kW downscaled model verify the effectiveness of the new balancing circuit. © 2010 IEEE.

DOI： 10.1109/TIA.2010.2102327

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

This paper describes voltage balancing of all the four split dc capacitors for a five-level diode-clamped PWM inverter intended for a transformerless mediumvoltage motor drive with a three-phase diode rectifier used as the front end. A dc-voltage-balancing circuit is installed on the dc link, and introduces a new midpoint-voltage-balancing method based on phase-shift control. As a result, the dc mean voltages of the four split dc capacitors can be balanced, independent of the inverter control. Experimental results obtained from the 200-V 5.5-kW downscale model verify that the dc mean voltage of the four split capacitors are balanced well under all the operating conditions. © 2010 IEEE.

DOI： 10.1109/IPEC.2010.5543254

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

This paper proposes a new dc-voltage-balancing circuit for a five-level diode-clamped inverter intended for a medium-voltage motor drive. This circuit consists of two unidirectional choppers and a single coupled inductor with two galvanically-isolated windings. The dc magnetic fluxes in the magnetic core, which are generated by the two windings, cancel out each other. Therefore, the inductor does not generate any dc-magnetic flux in the magnetic core. This makes the inductor compact by a factor of six compared to previously used balancing circuits containing two noncoupled inductors. Experimental results obtained from a 200-V 5.5-kW downscaled model verify that the dc mean voltages of the four split dc capacitors are balanced well under all operating conditions. © 2010 the Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejias.130.677

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