• IEIE Transactions on Smart Processing and Computing
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• v.5 no.1
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• pp.35-42
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• 2016

Developments in power electronics have enabled the widespread application of Pulse Width Modulation (PWM) inverters, notably for connecting renewable systems to the grid. This study demonstrates that a high-quality power can be achieved using a stand-alone inverter, whereby the comparison between the power quality of the stand-alone inverter with battery storage (off-grid) and the power quality of the utility network is presented. Multi-loop control techniques for a single phase stand-alone inverter are used. A capacitor current control is used to give active damping and enhance the transient and steady state inverter performance. A capacitor current control is cheaper than the inductor current control, where a small current sensing resistor is used. The output voltage control is used to improve the system performance and also control the output voltage. The inner control loop uses a proportional gain current controller and the outer loop is implemented using internal model control proportional-integral-derivative to ensure stability. The optimal controls are achieved by using the Sisotool tool in MATLAB/Simulink. The outcome of the control scheme of the numerical model of the stand-alone inverter has a smooth and good dynamic performance, but also a strong robustness to load variations. The numerical model of the stand-alone inverter and its power quality are presented, and the power quality is shown to meet the IEEE 519-2014. Furthermore, the power quality of the off-grid system is measured experimentally and compared with the grid power, showing power quality of off-grid system to be better than that of the utility network.

• Journal of Power Electronics
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• v.7 no.3
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• pp.246-256
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• 2007

In this paper, a novel type auxiliary active edge resonant snubber assisted zero current soft switching pulse modulation Single-Ended Push Pull (SEPP) series load resonant inverter using IGBT power modules is proposed for cost effective consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each switching mode's equivalent operating circuits. The new multi resonant high-frequency inverter with series load resonance and edge resonance can regulate its high frequency output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of the asymmetrical pulse width modulation (PWM) control scheme. Brand-new consumer IH products using the proposed ZCS-PWM series load resonant SEPP high-frequency inverter using IGBTs is evaluated and discussed as compared with conventional high-frequency inverters on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM as well as to improve efficiency, the high frequency pulse density modulation (PDM) strategy is demonstrated for high frequency multi-resonant inverters. Its practical effectiveness is substantially proved from an application point of view.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1235-1244
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• 2018

The application of shunt capacitor banks and underground cables typically induces resonance in power distribution systems. In this study, the propagation of resonance in a microgrid (MG) with inverter-based distributed generators (IBDGs) is investigated. If resonances are not properly damped, then the output current of the inverters may experience distortion via resonance propagation due to the adverse effect of resonances on MG power quality. This study presents a conceptual method for identifying resonances and related issues in multi-inverter systems. For this purpose, existing resonances are identified using modal impedance analysis. However, some resonances may be undetectable when this method is used. Thus, the resonances are investigated using the proposed method based on the frequency response of a closed-loop MG equivalent circuit. After analyzing resonance propagation in the MG, an effective virtual impedance damping method is used in the IBDG control system to damp the resonances. Results demonstrate the effectiveness of the proposed method in compensating for existing resonances.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.1
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• pp.36-41
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• 2004

In this paper a large scale STATCOM using double-connected multi-step inverter is proposed and operating principle along with control method is detailed. A simple auxiliary circuit including an interphase transformer is employed to improve output voltage waveform of 12-step into 36-step. The proposed scheme could be a cost effective approach in high power applications such as 10MVar to 30MVar STATCOM. Experimental results from a 2KVA laboratory prototype show validity of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.797-806
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• 2000

In this paper, the torque characteristics and the bar loss distribution are analyzed when a general cage induction motor with skewed slots is fed by a 6-step inverter. For the electromagnetic analysis, time-stepping finite element method is used. And the multi-slice technique and sliding surface technique are respectively utilized to consider the skew effect and the rotation of the rotor. As a result, the effects of skewed rotor bar and the inverter output voltage on the characteristics of the torque and bar loss in the rotor are investigated. The simulation results are verified by measurement of flux density distribution axially in the stator teeth.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.6 no.6
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• pp.32-41
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• 1992

In this paper, an advanced Pulse Width Modulation Inverter strategy for driving a variable-speed induction motor is introduced. A switching pattern making use of the near-proportionality of voltage and frequency in AC machines operating with constant flux was computed. At low magnitudes and ow frequencies of the fundamental, many more harmonics are eliminated than at high magnitudes and frequencies. In order to keep the inverter switching frequency constant over the output frequency range, the chopping frequency is diminished as the frequency of the fundamental increases. Using these modulation strategy, the harmonics components of PWM inverter are efficiently eliminated.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.1
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• pp.59-65
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• 2021

This study proposes a dead-time implementation method suitable for cell voltage control of a cascaded H-bridge (CHB) inverter. The PWM module of an existing microcontroller cannot generate a maximum voltage due to the dead-time effect when used as the cell controller of the CHB inverter. In the proposed method, the operation method of the PWM module was changed without using the dead time module included in the existing microcontroller, so that the cell output voltage can be increased to the maximum voltage without voltage discontinuity. During the maximum voltage generation period, the full turn-on state can be maintained without unnecessary switching. The validity of the proposed method is confirmed through an experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.6
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• pp.429-436
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• 2021

The design of a gate driver power supply for a three-phase inverter using a silicon carbide (SiC) MOSFET. The requirements for the power supply circuit of the gate driver for the SiC MOSFET are investigated, and a flyback converter using multiple transformers is used to make the four isolated power supplies. The proposed method has the advantage of easily constructing the power supply circuit in a limited space as compared with a multi-output flyback converter using a single core. The power supply circuit for the three-phase SiC MOSFET inverter for driving an AC motor is designed and implemented. The operation and validity of the implemented circuit are verified through simulations and experiments.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1821-1834
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• 2017

Medium voltage control applications due to obtain better output voltage and reduced electro-magnetic interference multi level inverter is used. In closed loop control with inverter, the PI controller does not operate satisfactorily when the operating point changes. This paper presents the performance of Co-Efficient diagram PI controller based indirect vector controlled induction motor drive fed from three-level inverter under different operating conditions (dynamic and steady state). The proposed Co-Efficient diagram PI controller based three level inverter significantly reduces the torque ripple compared to that of conventional PI controller. The performance of the indirect vector controlled induction motor drive has been simulated at different operating conditions. For three-level inverter control, a simplified space vector modulation technique is implemented, which reduces the coordinate transformations complications in the algorithms. The performance parameters, torque ripple contents and THD of induction motor drive with three-level inverter is compared under different operating conditions using CDM-PI and conventional PI controllers.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.54-60
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• 2005

In a $CO_2$ inverter welding machine, stable arcs can be generated and a welding performance that is a goal of welding can be improved when stable electric power with a low voltage and a high current is supplied to a electrode that is the secondary part (output load terminal) and the base metal. For such a stable power supply, therefore, the AC arc welding machine, the thyristor welder, and the inverter welder have been developed in order according to development of the power electronics techniques. Up to now, the thyristor welding machine is still broadly used but the application volume is gradually reduced by development of the inverter welder. Because the welding performance of the inverter welder is very good and the weight and size of the welder is remarkably light and small. The final goal of this research is to develop the voltage loss compensator that is a drawback of the inverter welder and improve the welding performance using the developed compensator.