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In this paper, we propose the control method of a peak shaving system for an electric injection molding machine (EIMM). The peak power shaver consists of a multiphase bidirectional dc–dc converter and supercapacitors (SCs), and is connected to a dc link of the inverter fed injection motor drive system of the EIMM. In the proposed control method, electric power is stored in the SCs through the multiphase bidirectional dc–dc converter with a pulsewidth-modulation rectifier while the injection motor is at rest. When the injection motor is accelerating, the stored power in the SCs together with the power from the distribution feeders is supplied to the injection motor. Thus, the peak power can be shaved. The basic principle of the proposed control method is discussed in detail, then confirmed by digital computer simulation and experimental setup. The simulation and experimental results demonstrate that the peak power is shaved by 70% using the peak power shaving system. [ABSTRACT FROM PUBLISHER]

Gallium-nitride-field-effect transistors (GaN-FETs) are promising switching devices with fast switching capability. However, they commonly have low gate threshold voltage, suffering from susceptibility to the false triggering. Particularly, the oscillatory false triggering, i.e., a self-sustaining repetitive false triggering, can occur after a fast switching, which is a severe obstacle for industrial applications. The purpose of this paper is to elucidate the design instruction for preventing this phenomenon. The oscillatory false triggering is known to be caused by the parasitic oscillator circuit formed of a GaN-FET, its parasitic capacitance and the parasitic inductance of the wiring. This paper analyzed the nonoscillatory condition of this oscillator. The result revealed an appropriate ratio between the gate-drain capacitance and the common-source inductance is a key to prevent the oscillatory false triggering. Experiment successfully verified this analysis result, supporting the effectiveness of the appropriate design of this ratio for preventing the oscillatory false triggering. [ABSTRACT FROM AUTHOR]

Switched reluctance motors (SRMs) have recently attracted researchers’ attention owing to their robust mechanical construction, high thermal tolerance, and strong cost-effectiveness, which are promising for vehicle propulsion. However, they tend to generate large ripples in the torque and input currents to the inverter; this deteriorates the driving comfort, and damages the battery lifetime. Preceding articles have investigated using the phase currents of SRMs to eliminate these ripples. However, these articles had difficulties in sufficiently eliminating these ripples in operations under magnetic saturation. This article further evolves one of these preceding articles, and proposes a derivation method for the phase-current waveform for improving the elimination of the torque and input-current ripples in operation under magnetic saturation. The proposed method analytically determines the phase-current waveform based on a nonlinear behavior model of the SRM while considering the magnetic saturation. A finite-element-method-based simulation and experiment are performed to evaluate the proposed method. These results reveal the successful reduction of the torque and input-current ripples under the magnetic saturation relative to a preceding study, supporting the appropriateness of the proposed method. [ABSTRACT FROM AUTHOR]

Wide-bandgap semiconductors such as silicon carbide (SiC) and gallium nitride (GaN) are promising materials for next-generation power devices. We have fabricated a normally on GaN-based high-electron-mobility transistor (GaN HEMT) for power electronic converters. In this paper, the current collapse phenomena, which are distinctive characteristics of GaN devices, are evaluated in detail for several voltages with two switching frequencies. We also evaluate a gate drive circuit that we previously proposed for the normally on GaN HEMT with a single positive voltage source. We construct and test prototype circuits for a boost-type dc–dc converter and a single-phase full-bridge inverter with a gate drive circuit. The problems to be solved for the normally on GaN HEMT, which has a (static) voltage rating of over 600 V, are clarified on the basis of the experimental results. [ABSTRACT FROM AUTHOR]

In this paper, the practical impedance approach steady-state analysis in the frequency domain for the three-phase self-excited induction generator (SEIG) with squirrel-cage rotor is presented along with its operating performance evaluations. The three-phase SEIG is driven by a variable-speed prime mover(VSPM) in addition to a constant-speed prime mover (CSPM) such as a wind turbine and a micro gas turbine for clean alternative renewable energy in rural areas. The basic steady-state characteristics of the VSPM are considered in the three-phase SEIG approximate equivalent circuit and the operating performance of the three-phase SEIG coupled with a VSPM and/or a CSPM are evaluated and discussed online under the conditions related to the speed changes of the prime mover and the electrical inductive load power variations with simple computation processing procedures. A three-phase SEIG prototype setup with a VSPM is implemented for small-scale clean renewable and alter- native energy utilizations. The experimental performance results give good agreement with those obtained from the simulation results. Furthermore, a proportional-integral (P1) closed-loop feedback voltage regulation of the three-phase SEIG driven by the VSPM on the basis of the static var compensator (SVC) composed of the thyristor phase-controlled reactor in parallel with the thyristor switched capacitor and the fixed-excitation capacitor bank is designed and considered for the wind generation as a renewable power conditioner. The simulation analysis and experimental results obtained from the three-phase SEIG with SVC for its voltage regulation prove the practical effectiveness of the additional SVC with the P1-controller-based feedback loop in steady-state operation in terms of high performance with low cost. [ABSTRACT FROM AUTHOR]

Litz wire has been widely utilized in power transformers and inductors as a wire with low copper loss at high-frequency operation. The Litz wire is commonly made of many thin isolated strands twisted in multiple levels. Due to its complicated structure, the copper loss prediction of the Litz wire has been difficult, hindering the design optimization of the Litz wire structure. To overcome this difficulty, preceding studies have investigated the analytical copper loss models of the constituting elements of the Litz wire, i.e., the strands and the bundles of strands. The purpose of this article is to propose an analytical copper loss model of the Litz wire by utilizing these preceding knowledge. The proposed model is formulated only with parameters that can be measured by basic testing instruments. Besides, the proposed model considers the bundle structure of the Litz wire, which affects the local ac current distribution, and the twisting pitch, which causes the inclination of the Litz wire strands. The proposed model was tested by comparing the analytical prediction and experimental measurements of the ac resistance of commercially available Litz wires. As a result, the predicted ac resistance showed good agreement with the measured ac resistance, suggesting the appropriateness of the proposed model. [ABSTRACT FROM AUTHOR]

Switched reluctance motor (SRM) is recently emerging as a cost-effective but mechanically and thermally robust motor for vehicle propulsion. However, the conventional driving method of the SRM causes a large input current and torque ripples, both of which are scarcely acceptable for vehicle application. Recently, a promising driving method has been proposed that tunes the phase current to eliminate the input current and torque ripples simultaneously, although this method suffers from large copper loss when applied to the normal SRMs. To solve this problem, this article proposes simultaneous tuning of the rotor shape in combination with the recently proposed driving method, which includes only tuning of the phase current. Tuning of the rotor shape is targeted at minimizing the copper loss. Meanwhile, the stator structure is the same as the normal SRM design. The proposed approach was revealed to reduce the effective value of the phase current by 18% in simulation and by 23% in experiment compared with the recently proposed driving method, without increasing the input current and torque ripples. This result suggests the effectiveness of tuning both the rotor shape and the phase current for applying SRMs to vehicle propulsion. [ABSTRACT FROM AUTHOR]

This paper proposes a novel simple reactive power control strategy for the active load balancer (ALB) in three-phase four-wire distribution systems. The proposed reactive power control strategy may be applicable for adjustment of the source-side power factor under the balanced load condition. Only dc capacitor voltage control is used in the proposed control strategy. Therefore, the calculation blocks of the active and reactive components of the load currents are not necessary. The authors, thus, offer the simplest control strategy to control reactive power under the balanced load condition on three-phase four-wire distribution feeders. The basic principle of dc-capacitor-voltage-control-based reactive power control strategy is discussed in detail and then confirmed by digital computer simulation. A prototype experimental system was constructed and tested. Experimental results demonstrate that balanced source currents with reactive power control are achieved on three-phase four-wire distribution feeders. These experimental results also demonstrate that controlling the reactive power reduces the required power rating of the ALB compared with that of the conventional unity power factor control strategy. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a new control algorithm to reduce the capacity of a previously proposed smart charger for electric vehicles (EVs) on single-phase three-wire distribution feeders with reactive power control. The basic principle of the proposed control algorithm is discussed in detail. It is shown that controlling the reactive power on the source side reduces the capacity of the previously proposed smart charger. A digital computer simulation is implemented to confirm the validity of the proposed control algorithm using PSIM software. A prototype experimental model is also constructed and tested. Experimental results demonstrate that balanced source currents with a power factor of 0.9, which is acceptable for Japanese home appliances, are obtained on the secondary side of the pole-mounted distribution transformer during both the battery charging and discharging operations in EVs. The capacity of dc capacitor CDC is also reduced by 37% with the proposed reactive power control algorithm. [ABSTRACT FROM AUTHOR]

In this paper, we propose a smart charger for electric vehicles with a power-quality compensator. The proposed smart charger consists of four-leg insulated-gate bipolar transistors (IGBTs). Three legs are used for a single-phase full-bridge-based pulsewidth-modulated (PWM) rectifier, which converts power from ac to dc during the battery-charging operation or from dc to ac during the battery-discharging operation. This PWM rectifier can compensate reactive and unbalanced active currents on single-phase three-wire distribution systems because the third leg is connected to the neutral line of single-phase three-wire distribution feeders. The fourth leg is used as a bidirectional dc–dc converter for battery-charging and battery-discharging operations. The three-leg PWM rectifier uses only constant dc-capacitor voltage control, which is commonly used in active power line conditioners. Thus, the authors have developed the simplest possible control method for a single-phase power-quality compensator. The basic principle of the proposed smart charger is discussed in detail and then confirmed by digital computer simulation using PSIM software. A prototype experimental model is constructed and tested. Experimental results demonstrate that balanced source currents are obtained on the secondary side of the pole-mounted distribution transformer for battery-charging and battery-discharging operations. [ABSTRACT FROM PUBLISHER]

Proposes a precise tracking servo control system using the compact traveling-wave-type ultrasonic motor. Problems of the speed servo control system incorporating the ultrasonic motor developed in Japan; Composition of the algorithm of the proposed control scheme; Experiments that demonstrate and evaluate the proposed control system.