717 publications from this institution
This paper presents a specially designed third-order resonant circuit intended to achieve fast switching operation for a voltage-source series-resonant inverter using four MOSFETs. The third-order resonant current superimposed on a sinusoidal load current helps to quickly charge or discharge the output capacitance of each MOSFET. This results not only in a reduction of the commutation period which is required to turn the MOSFET on and off, but also in an improvement of the displacement factor at the output of the inverter. Moreover, the third-order resonant circuit acts as a low-pass filter to suppress the parasitic oscillation between line inductance and stray capacitance. The viability and effectiveness of the third-order resonant circuit is verified by a 2 MHz 2 kW prototype inverter developed for a low-temperature plasma generator.
Corona discharge treaters have been used to treat surface of polyethylene films and to improve affinity for inks. The features of a resonant inverter system using IGBT's for corona discharge treaters developed in this paper are as follows. (1) No external reactors or capacitors are necessary because a series resonant circuit is composed of a leakage inductor of a step-up transformer and a capacitor between discharge electrodes of the treater. (2) A three-phase diode rectifier can be used because the output power is controlled by adjusting output power factor of the inverter. (3) A capacitor is connected between a collector and emitter of IGBT's to reduce switching losses.An optimal design of the capacitor is done by utilizing an analog circuit simulator. The authors propose an equivalent circuit of the IGBT because there may be no exact IGBT model for analog circuit simulators. The validity of the equivalent circuit is verified by comparing experimental results with simulated ones. As a result, it is shown experimentally that the optimal capacitor, which is determined by the simulation developed in this papaer, leading to higher efficiency.
This paper deals with a hybrid shunt active filter for harmonic compensation of a three-phase diode rectifier in a 480-V adjustable-speed drive system. The hybrid filter is formed by a three-phase single-tuned current LC filter for the 7-th harmonic frequency and a small-rated three-phase voltage-source PWM inverter. Computer simulation is carried out to compare the hybrid filter with a pure shunt active filter in terms of circuit configuration and filtering performance. The simulation results indicate effectiveness and viability of the hybrid filter. In addition, theoretical analysis confirms the validity of the simulation results.
This paper proposes a small-sized passive electromagnetic interference (EMI) filter for the purpose of eliminating high-frequency shaft voltage and ground leakage current from an ac motor driven by a voltage-source pulsewidth-modulation inverter. The filter requires access to the neutral point of the motor. A common-mode inductor is connected between the inverter and the motor. The neutral point of the motor is connected to the dc-bus midpoint via a resistor. The dc-bus midpoint is created by using two capacitors in series across the dc positive and negative buses. This unique circuit configuration makes the common-mode inductor effective in reducing the common-mode voltage appearing at the motor terminals. The validity and effectiveness of the EMI filter is verified by experimental results obtained from a 5-kVA laboratory system.
The superconducting magnetic leviation railway system (MAGLEV) under development in Japan uses pulse‐width‐modulation (PWM) inverter for driving a linear synchronous motor (LSM). The inverter output voltage contains nonnegligible harmonics which cause harmonic resonances in the LSM system, and therefore harmonics of the output voltage have been analyzed in order to control such harmonic resonances. This paper applies a third‐harmonic injection method to the inverter for the purpose of enhancing the output voltage without changing the circuit configuration. It performs harmonic analysis of the output voltage of the inverter based on the third‐harmonic injection. Validity of the harmonic analysis is verified by computer simulation. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 71–78, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ).
This paper starts with a historical review of the family of modular multilevel cascade converters, and the topology and terminology of the family. Then, it answers the following question: ‘What motivated the author to apply phase‐shifted‐carrier pulse‐width modulation (PSC PWM) to the family?’ The success in academic research on this application owes to integrating inter‐cluster balancing or inter‐arm balancing control into the middle layer of a hierarchical control system consisting of three layers. This integration makes it easy to expand the PSC PWM to any bridge‐cell or chopper‐cell count per cluster or arm. Finally, this paper ends with future scenarios of a few promising family members and their practical applications, from the personal experience and view of the author. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.
This paper focuses on fault-tolerant control for a battery energy storage system based on a three-phase multilevel cascade PWM (pulse-width-modulation) converter with star configuration. It enables continuous operation and maintains SOC (state-of-charge) balancing of operating battery units even during the occurrence of a converter-cell or battery-unit failure. This enhances both system reliability and availability. A 200-V, 10-kW, 3.6-kWh laboratory system combining a three-phase cascade PWM converter with nine NiMH (Nickel-metal-hydride) battery units is designed, constructed, and tested to verify the validity and effectiveness of the proposed fault-tolerant control.
This paper provides a multiple motor drive using modular multilevel cascade converters (MMCCs) with galvanic isolation achieved by medium-frequency transformers. The motor drive is suitable for large-capacity pump and conveyor applications where multiple motors are required. A mitigating control method designed for the motor drive can reduce inherent capacitor-voltage fluctuation in each floating dc capacitor. As a result, the capacitance values can be dramatically reduced, compared to the already-existing MMCCs. Simulated waveforms verify the effectiveness of the multiple motor drives and its mitigating control method. These results are obtained from two 6-kV 2.5-MW loads fed by a converter system consisting of a single supply-side MMCC, two load-side MMCCs, and two 450-Hz single-phase transformers.
A modular multilevel converter (MMC) is one of the next-generation multilevel PWM converters intended for high- or medium-voltage power conversion without transformers. The MMC consists of cascade connection of multiple bidirectional PWM chopper-cells, thus requiring voltage-balancing control of their chopper-cells. However, no paper or article has been presented or published on the voltage-balancing control with theoretical and experimental verifications. This paper deals with two types of modular multilevel PWM converters with focus on their circuit configurations and voltage-balancing control. Combination of averaging and balancing controls enables the MMCs to achieve voltage balancing without any external circuit. The viability of the MMCs as well as the effectiveness of the PWM control method is confirmed by simulation and experiment.
This paper proposes an “active common-mode noise canceler” that is capable of eliminating the common-mode voltage produced by a voltage source PWM (pulsewidth modulated) inverter. It generates a compensating voltage which has the same amplitude as, but the opposite phase to, the common-mode voltage produced by the PWM inverter. The compensating voltage is superimposed on the inverter output by a common-mode transformer. As a result, the common-mode voltage applied to the load is canceled completely. The design method of the active common-mode noise canceler is also presented in detail. A prototype has been constructed and tested to verify the effectiveness for an induction motor drive system of 3.7 kW using an IGBT (insulated gate bipolar transistor) inverter. Some experimental results show that the proposed active common-mode noise canceler makes a significant contribution to eliminating the common-mode current or the ground current, and it prevents an electric shock from being received by anyone handling it. © 1998 Scripta Technica, Electr Eng Jpn, 124(3): 64–72, 1998
Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. These motors are characterized by integration of switched reluctance motors and magnetic bearings. It is essential for a control system to consider magnetic saturation in real time in order to realize stable operation at a full torque load. Thus, this paper proposes a method for fast calculation of radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation. It is shown experimentally that the proposed method is effective in calculating the radial force and the torque under conditions of magnetic saturation.
The emergence of power semiconductor devices such as insulated-gate bipolar transistors (IGBTs) or injection-enhanced gate transistors (IEGTs) and gate-commutated turn-off (GCT) thyristors or integrated gate-commutated thyristors (IGCTs) enables power conversion systems to expand into utility and industry applications. This paper describes the present status of power electronics, and its future prospects and directions in the 21st century.
This paper deals with a harmonic current-free AC/DC power conversion system which is characterized by the integration of a small-rated series active filter with a large-rated double-series diode rectifier. The stability of the active filter based on feedback control is discussed theoretically, taking into account delay time in the control circuit. As a result, it is revealed that the delay time may produce a bad effect on stability, especially when the power conversion system is installed on a stiff power system with low system inductance. The authors propose a viable way of reducing the effect of delay time on the system stability. Analysis in the frequency domain enables us to know how much the system stability is improved in terms of gain and phase margins. A switching-ripple filter is designed to obtain good filtering performance without affecting the system stability. Experimental results obtained from a 20-kW laboratory system verify the validity of the developed theory, and confirm the viability and effectiveness of the proposed control circuit.
A novel approach to compensate for harmonics in power systems is proposed. The approach differs from conventional passive and active filters in its compensation principle. A practical system configuration to implement the approach is presented. It consists of a small-VA-rating PWM (pulsewidth-modulated) converter and a passive filter. The compensation principle is described, and compensation characteristics are examined theoretically and experimentally. The practicability and validity of the approach are experimentally demonstrated. >
This paper discusses “the p – q theory” and “the cross‐vector theory” in three‐phase four‐wire systems, with the focus on similarities and differences between the two theories. They are perfectly identical if no zero‐sequence voltage is included in a three‐phase three‐wire system. However, they are different in definition of the instantaneous active power and instantaneous reactive power in each phase if a zero‐sequence voltage or current is included in a three‐phase four‐wire system. Based on both theory and computer simulation, this paper leads to the following conclusions: An instantaneous reactive‐power compensator without energy storage components can fully compensate for the neutral current even in a three‐phase four‐wire system including a zero‐sequence voltage or current, when a proposed control strategy based on the p – q theory is applied: However, the compensator cannot compensate for the neutral current fully, when a conventional control strategy based on the cross‐vector theory is applied. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 74–86, 2001
