• Journal of Power Electronics
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• v.14 no.2
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• pp.324-340
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• 2014

Recent developments in power electronics technology have spurred interest in the use of renewable energy sources as distributed generation (DG) generators. The key component in DG generators is a grid-connected inverter that serves as an effective interface between the renewable energy source and the utility grid. The multifunctional inverter (MFI) is special type of grid-connected inverter that has elicited much attention in recent years. MFIs not only generate power for DGs but also provide increased functionality through improved power quality and voltage and reactive power support; thus, the capability of the auxiliary service for the utility grid is improved. This paper presents a comprehensive review of the various MFI system configurations for single-phase (two-wire) and three-phase (three- or four-wire) systems and control strategies for the compensation of different power quality problems. The advances in practical applications and recent research on MFIs are presented through a review of nearly 200 papers.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.2
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• pp.80-86
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• 2003

In this paper, a new three-phase voltage-source inverter topology for high voltage and high Power applications is proposed to improve the quality of output voltage waveform. A chain converter which is used as an auxiliary circuit generates a ripple voltage and injects it to the conventional 12-step inverter. Thus, the injection of the ripple voltage results in 36-step operation with a link and 60-step operation with two links. The proposed inverter is compared to the conventional multilevel inverter in the viewpoint of ratings of phase- shifting transformers, switching devices and capacitors employed. The proposed scheme is simple to control capacitor voltages compared to the conventional schems and is cost effective for high voltage and high power application over several tens of MVA. The proposed approach is validated through simulation, and the experimental results are provided from a 2KVA laboratory prototype.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2284-2293
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• 2016

With the rapid development of clean energy, photovoltaic (PV) generation has been utilized in the harmonic compensation of power systems. This paper presents a novel multi-function PV micro-inverter with three stages (pseudo-two-stage). It can inject active power and compensate harmonic currents in the power grid at the same time. In order to keep the micro-inverter working under the maximum allowable output power, an optimized capacity limitation strategy is presented. Moreover, the harmonic compensation can be adjusted according to the customized requirements of power quality. Additionally, a phase shedding strategy in the DC/DC stage is introduced to improve the efficiency of parallel Boost converters in a wide range. Compared with existing capacity limitation methods, the proposed strategy shows better performance and energy efficiency. Simulations and experiments verify the feasibility of the micro-inverter and the effectiveness of the strategy.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.220-226
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• 2010

In this paper, the static overmodulation is proposed for the 2-phase full bridge inverter. The overmodulation strategy increases a fundamental output voltage and improves a voltage utilization up to the maximum in the overmodulation range. The linear modulation range and static overmodulation range are defined in the 2-phase full bridge inverter. The overmodulation strategies which increase a voltage utilization until the 4-step mode by linearization of the output voltage in overmodulation range are proposed. To maintain a linearity of the relation between a reference voltage and a fundamental output voltage, this paper suggests a compensation voltage, whose magnitude or phase is modified to the proposed control scheme. Simulation and experimentation results demonstrate the effectiveness of the proposed algorithms.

• Journal of Power Electronics
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• v.14 no.1
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• pp.115-124
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• 2014

This paper presents the implementation of two-arm modulation (TAM) technique for the independent control of a two-induction motor drive fed by a five-leg inverter (FLI). A carrier-based space vector pulse width modulation technique for TAM is proposed to generate switching signals for FLI. Two independent three-phase space vector modulators are utilized to control two motors. The motor drive system applies two separate indirect field-oriented control methods. The stationary voltage outputs from the vector control are synthesized in the three-phase space vector modulator to generate switching signals for FLI. The performance of the independent control of the motors and the voltage utilization factor are likewise analyzed. Simulation and experimental results verify the effectiveness of the proposed method for the independent control of the two-motor drive system. The proposed technique is successfully validated by dSPACE DS1103 experimental work.

• Journal of Power Electronics
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• v.14 no.3
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• pp.507-518
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• 2014

This paper presents a new cascaded asymmetrical single phase multilevel converter with a lower number of power semiconductor switches and isolated DC sources. Therefore, the number of power electronic devices, converter losses, size, and cost are reduced. The proposed multilevel converter topology consists of two H-bridges connected in cascaded configuration. One H-bridge operates at a high frequency (high frequency inverter) and is capable of developing a two level output while the other H-bridge operates at the fundamental frequency (low frequency inverter) and is capable of developing a multilevel output. The addition of each power electronic switch to the low frequency inverter increases the number of levels by four. This paper also introduces a hybrid switching algorithm which uses very simple arithmetic and logical operations. The simplified hybrid switching algorithm is generalized for any number of levels. The proposed simplified switching algorithm is developed using a TMS320F2812 DSP board. The operation and performance of the proposed multilevel converter are verified by simulations using MATLAB/SIMULINK and experimental results.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.538-545
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• 2012

In this paper a novel cascaded transformer multilevel inverter is proposed. Each basic unit of the inverter includes two DC sources, single phase transformers and semiconductor switches. This inverter, which operates as symmetric and asymmetric, can output more number of voltage levels in the same number of the switching devices. Besides, the number of gate driving circuits is reduced, which leads to circuit size reduction and lower power consumption in the driving circuits. Moreover, several methods to determination of transformers turn ratio in proposed inverter are presented. Theoretical analysis, simulation results using MATLAB/SIMULINK and experimental results are provided to verify the operation of the suggested inverter.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1582-1590
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• 2019

A new method for reducing the common-mode current generated by the voltage variations in a two-inverter air conditioner system by applying a synchronized pulse-width modulation (PWM) strategy is proposed. The PWM signals of the master-mode inverter are generated based on the reference voltage, while those of the slave-mode inverter are output in the opposite direction when the master-mode inverter changes its switching state. However, the slave-mode control results in a mismatch between the reference voltage and the actual output voltage that is modified by synchronized control operation. The proposed method is capable of reducing and controlling this voltage error by performing signal selection in the vector space of the slave-mode inverter, which mitigates the distortion of the phase current. The efficacy of this method in reducing conducted emissions has been validated both theoretically and experimentally.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.3
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• pp.145-150
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• 2013

A novel AC to DC PWM converters with unity input power factor are proposed to overcome the above shortcoming. The main function of these converters is to shape the input line current to force it exactly in phase with the input AC voltage. Therefore, the input power factor can be improved to near unity and the input current harmonics can be eliminated. In this paper, half-bridge converter with two active switches and two diodes are utilized for low-cost type UPS configuration. By having only two semiconductors in the current path at any time, losses can be reduced over the conventional boost topology. Also, this converter provides controllable dc-link voltage, high power factor, and low cost type converter by simple power circuits. Simulation results show that the proposed half-bridge converter/inverter control technique can be applied to single-phase low-cost type UPS systems successfully.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1477-1485
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• 2019

This paper proposes an effective model predictive current control (MPCC) that involves using 10 virtual voltage vectors to reduce the current harmonics and common-mode voltage (CMV) for a two-level five-phase voltage source inverter (VSI). In the proposed scheme, 10 virtual voltage vectors are included to reduce the CMV and low-order current harmonics. These virtual voltage vectors are employed as the input control set for the MPCC. Among the 10 virtual voltage vectors, two are applied throughout the whole sampling period to reduce current ripples. The two selected virtual voltage vectors are based on location information of the reference voltage vector, and their duration times are calculated using a simple algorithm. This significantly reduces the computational burden. Simulation and experimental results are provided to verify the effectiveness of the proposed scheme.