• Journal of Power Electronics
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• v.16 no.6
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• pp.2099-2108
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• 2016

The cascaded multilevel converter is widely adopted to medium/high voltage and high power electronic applications due to the small harmonic components of the output voltage and the facilitation of modularity. In this paper, the operation principle of a T-type H-bridge topology is investigated in detail, and a carrier phase shifted pulse width modulation (CPS-PWM) based control method is proposed for this topology. Taking a virtual five-level waveform achieved by a unipolar double frequency CPS-PWM as the output object, PWM signals of the T-type H-bridge can be obtained by reverse derivation according to its switching modes. In addition, a control method for the T-type H-bridge based cascaded multilevel converter is introduced. Then a single-phase T-type H-bridge cascaded multilevel static var generator (SVG) prototype is built, and a repetitive controller based compound current control strategy is designed with the DC-link voltage balancing control scheme analyzed. Finally, simulation and experimental results validate the correctness and feasibility of the proposed modulation method and control strategy for T-type H-bridge based cascaded multilevel converters.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.5
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• pp.718-725
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• 2015

This paper proposes a novel level-shifted PWM (LS-PWM) strategy for fault tolerant cascaded multilevel inverter. Most proposed fault-tolerant operation methods in many of studies are based on a phase-shifted PWM (PS-PWM) method. To apply these methods to multilevel inverter systems using LS-PWM, two additional steps will be implemented. During the occurrence of a single-inverter-cell fault, the carrier bands scheme is reconfigured and modulation levels of inverter cells are reassigned in this proposed fault-tolerant operation. The proposed strategy performs balanced three-phase line-to-line voltages and line currents when a switching device fault occurs in a cascaded multilevel inverter using LS-PWM. Simulation and experimental results are included in the paper to verify the proposed method.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.278-282
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• 1990

In this paper, two different plusewidth modulation(PWM) for inverter and voltage control technique are described. Inverter output harmonics are harmful in induction motor drive because it lead to ripple torque and induction interference. In order to reduce or minimize losses, various forms of PWM strategy such as PM(Positive Modulation) and NM(Negative Modulation) are discussed.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1197-1207
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• 2014

Common-mode voltage (CMV) causes overvoltage stress to winding insulation and damages AC motors. CMV with high dv/dt causes leakage currents, which create noise problems for equipment installed near the converter. This study proposes a new pulse-width modulation (PWM) strategy for three-level T-type NPC inverters. This strategy substantially eliminates CMV. The principle for selecting suitable triangle carrier signals for the three-level T-type NPC is described. The proposed method can mitigate the peak value of CMV by 50% compared with the phase disposition pulse-width modulation method. Furthermore, the proposed method exhibits better harmonic spectrum and lower root mean square value for the CMV than those of the reduced-CMV method on the basis of the phase opposition disposition PWM scheme with modulation index higher than 0.5. The proposed modulation can easily be implemented using software without any additional hardware modifications. Both simulation and experimental results demonstrate that the proposed carrier phase-shift PWM method has good output waveform performance and reduces CMV.

• Journal of Power Electronics
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• v.16 no.3
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• pp.936-945
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• 2016

Large magnitude common-mode voltage (CMV) and its variation dv/dt have an adverse effect on motor drives that leads to early winding failure and bearing deterioration. For matrix converters, the switch states that connect each output line to a different input phase result in the lowest CMV among all of the valid switch states. To reduce the output CMV for matrix converters, this paper presents a new space vector modulation (SVM) strategy by utilizing these switch states. By this mean, the peak value and the root mean square of the CMV are dramatically decreased. In comparison with the conventional SVM methods this strategy has a similar computation overhead. Experiment results are shown to validate the effectiveness of the proposed modulation method.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1337-1344
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• 2013

This paper presents a simplified modulation strategy for the three-leg VSI fed two-winding induction motor. The strategy provides independent unbalanced voltage control for the main and auxiliary windings. This make the motor can be reversed rotation through the range of motor speed operation without limitation of voltage boost of the auxiliary winding. To study the advantages of the proposed drive, the experimental results such as voltage stresses, hysteresis band of the currents in locus, and also acoustic noise levels of the three-leg VSI are compared with those of the conventional two-leg topology. The results obviously show that the proposed technique achieves superior performance compared with the traditional scheme in case of dramatic increase of DC bus utilization, effective reduction of harmonic voltages content, and also significant enhancement of motor efficiency.

• Journal of Power Electronics
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• v.16 no.2
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• pp.490-497
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• 2016

The analysis of the switch status of each unit module of a cascaded multi-level inverter reveals that the working condition of the switch of a chopper arm causes unnecessary switching under the conventional unipolar sinusoidal pulse width modulation (SPWM). With an increase in the number of cascaded multilevel inverters, the superposition of unnecessary switching gradually occurs. In this work, we propose an improved SPWM strategy to reduce switching in cascaded multilevel inverters. Specifically, we analyze the switch state of the switch tube of a chopper arm of an H-bridge unit. The redundant switch is then removed, thereby reducing the switching frequency. Unlike the conventional unipolar SPWM technique, the improved SPWM method greatly reduces switching without altering the output quality of inverters. The conventional unipolar SPWM technique and the proposed method are applied to a five-level inverter. Simulation results show the superiority of the proposed strategy. Finally, a prototype is built in the laboratory. Experimental results verify the correctness of the proposed modulation strategy.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.283-284
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• 2013

This paper proposes a fault-tolerant strategy for indirect matrix converter (IMC) based on the concept of four-leg matrix converter in case of an open-circuit fault in the inverter stage. The proposed strategy can maintain the same output performance as the healthy condition during the faulty condition. Some simulated results are provided to verify the effectiveness of the proposed strategy.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.280-289
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• 2015

A high-efficiency full-bridge DC-DC converter with a current-doubler rectifier and an asymmetric pulse-width modulation is proposed. Through the asymmetric pulse-width modulation, the proposed converter achieves zero-voltage switching of power switches without the circulating currents. The proposed converter reduces the output current ripple through the current-doubler rectifier. A control strategy is suggested for the proposed converter to charge battery banks. A constant current and constant voltage charging is performed. The proposed converter achieved a higher efficiency compared with the conventional full-bridge DC-DC converter with a phase-shift modulation. The performance of the proposed converter is evaluated by the experimental results for a 1.0 kW prototype circuit.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.200-201
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• 2005

This paper is analyzed a new modulation method of OSW(Optimized Sine-Wave) modulation strategy for cascaded H-bridge multi-level inverter. The inverter structure was modified with the maximum output voltage level, and the switching angle was calculated easily to adjust the requested Vrms of the output. The suggested modulation method could make output waveform very close to the ideal sine wave, and the THD value was improved also remarkably.