• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.451-462
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• 2016

Photovoltaic energy conversion becomes main focus of many researches due to its promising potential as source for future electricity and has many advantages than the other alternative energy sources like wind, solar, ocean, biomass, geothermal etc. In Photovoltaic power generation multilevel inverters play a vital role in power conversion. The three different topologies, diode-clamped (neutral-point clamped) inverter, capacitor-clamped (flying capacitor) inverter and cascaded h-bridge multilevel inverter are widely used in these multilevel inverters. Among the three topologies, cascaded h-bridge multilevel inverter is more suitable for photovoltaic applications since each pv array can act as a separate dc source for each h-bridge module. This paper presents a single phase Cascaded H-bridge five level inverter for grid-connected photovoltaic application using sinusoidal pulse width modulation technique. This inverter output voltage waveform reduces the harmonics in the generated current and the filtering effort at the input. The control strategy allows the independent control of each dc-link voltages and tracks the maximum power point of PV strings. This topology can inject to the grid sinusoidal input currents with unity power factor and achieves low harmonic distortion. A PID control algorithm is implemented in Arm Processor LPC2148. The validity of the proposed inverter is verified through simulation and is implemented in a single phase 100W prototype. The results of hardware are compared with simulation results. The proposed system offers improved performance over conventional three level inverter in terms of THD.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.134-139
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• 2005

This paper presents a cost effective quasi-resonant soft-switching PWM high frequency inverter with minimum circuit components. This inverter can achieve wider soft commutation, simpler power circuit configuration, smaller volumetric size, lower cost and wider power regulation range, higher-efficiency as compared with single ended quasi-resonant ZVS-PFM inverter and active voltage clamped quasi-resonant ZVS-PWM inverter. The operation principle of the proposed inverter is described on the basis of the simulation and experimental results, together with its operating performances in steady state. The operating performances of this unique proposed high frequency inverter based on ZVS and ZCS arms-related soft commutation principle is evaluated and discussed as compared with the active voltage-clamped ZVS-PWM inverter and a conventional single-ended ZVS-PFM inverter. The practical effectiveness of a novel type quasi-resonant soft-switching PWM high frequency inverter using IGBT is actually proved for consumer induction heated appliances as rice cooker, hot water producer, steamer and super heated steamer. The extended bidirectional circuit topology of quasi-resonant PWM high frequency inverter with minimum circuit components is demonstrated, which operate as the direct frequency changer.

• Journal of IKEEE
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• v.23 no.1
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• pp.53-57
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• 2019

In this paper, we propose a new Z-source inverter structure to reduce switching elements and PWM pulse control method. Z-network is connected between the inverter backplane and ground, rather than between the DC voltage and the inverter in an improved Z-source inverter. And the improved Z-source inverter has the advantages of limiting the capacitor inrush current and reducing the capacitor voltage stress. We have proposed a topology of a new type of switch-reduced improved Z-source inverter that reduces the number of switches from six to four in an improved Z-source inverter and developed a PWM control method suitable for the proposed topology. The characteristics and the performance of the proposed method were verified by using PSIM simulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1071-1079
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• 2007

In this paper, a novel space vector control method for isolated multi-level inverter using 3-phase low frequency transformers is proposed. This method is based on the simplification of the space-vector diagram of a five-level inverter using calculated table into fully programming method. The execution time of the proposed method is about same as that of the method using calculated table. Also, the proposed method is easily applied to other case level inverter. We applied this method into the 3-phase IHCML inverter using common arm. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformers could be reduced compare with an exiting 3-phase multi-level inverter using single phase transformer. In addition, this method generates very low harmonic distortion operation with nearly fundamental switching frequency. Finally, We tested multi-level inverter to clarify electric circuit and reasonableness through Matlab simulation and experiment by using prototype inverter.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.4_1
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• pp.559-567
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• 2020

As the renewable energy market grows, grid-connected inverters have been improving and expanding in several fields in recent years because energy conversion devices are the main components of solar systems. In this paper, a high-precision new grid-connected three-phase inverter system is proposed. The proposed system consists of a main inverter, a sub inverter and a transformer. The main inverter operates at a low switching frequency and high power and transmits power to the grid. A sub-inverter connected in series with the transmission line through a matching transformer operates at lower power than the main inverter to provide input values to the transformer. The transformer acts as a power supply according to the voltage compensation value. This study is based on the principle of operation of the UPFC(Unified Power Flow Controller) structure used to regulate power flow in AC transmission lines. The grid-connected inverter system proposed in this paper is implemented with high precision and high resolution. The proposed system was verified through its ability to enhance and ensure the safety of the proposed system through simulation and experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.5
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• pp.437-442
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• 2013

For open-end permanent magnet synchronous machine(PMSM) with dual inverter system, where one inverter is connected to the source and the other is flying, the dc link voltage of the flying inverter can be boosted through the machine. For this reason, when compared with single inverter drive system, higher voltage can be applied to PMSM, and higher torque can be generated in the flux weakening region. In this case, however, active and reactive powers are separately supplied by each inverter to maintain the dc link voltage of flying inverter. Therefore, the required flux weakening control is different from the conventional method for a single inverter drive system. This paper proposes the novel flux weakening control method which maximizes the active voltage component in a dual inverter PMSM drive system. The proposed method was demonstrated and verified through experimental results.

• Journal of Power Electronics
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• v.17 no.3
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• pp.777-787
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• 2017

A new single phase half-bridge cascaded multilevel inverter based series active power filter (SAPF) is proposed. The main parts of the inverter are presented in detail. With the proposed inverter topology, any compensation voltage reference can be easily obtained. Therefore, the inverter acts as a harmonic source when the reference is a non-sinusoidal signal. A 31-level inverter based SAPF with the proposed topology, is manufactured and the voltage harmonics of the load connected to the point of common coupling (PCC) are compensated. There is no need for a parallel passive filter (PPF) since the main purpose of the paper is to represent the compensation capability of the SAPF without a PPF. It is aimed to compensate the voltage harmonics of the load fed by a non-sinusoidal supply using the proposed inverter. The validity of the proposed inverter based SAPF is verified by simulation as well as experimental study. The system efficiency is also measured in this study. Both simulation and experimental results show that the proposed multilevel inverter is suitable for SAPF applications.

• Journal of Power Electronics
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• v.18 no.1
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• pp.277-288
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• 2018

Wireless inductive power transfer (IPT) technology is used in many applications today. A compact and high-frequency primary side inverter is one of the most important parts of a WPT system. In this study, a modified class EF-type voltage-fed multi-resonant inverter has been proposed for WPT application at a frequency range of 85-100 kHz. Instead of an infinite input choke inductor, a resonant inductor is used to reduce loss and power density. The peak voltage stress across the MOSFET has been reduced to almost 60% from a class-E inverter using a passive clamping circuit. A simple yet effective design procedure has been presented to calculate the various component values of the proposed inverter. The overall system is simulated using MATLAB/SimPowerSystem to verify the theoretical concepts. A 500-W prototype was built and tested to validate the simulated results. The inverter exhibited 90% efficiency at nearly perfect alignment condition, and efficiency reduced gradually with the misalignment of WPT coils. The proposed inverter maintains zero-voltage switching (ZVS) during considerable load changes and possesses all the inherent advantages of class E-type inverters.

• Journal of Korea Multimedia Society
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• v.25 no.10
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• pp.1448-1456
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• 2022

This paper studies a model to diagnose efficiency reduction of inverter using Multilayer Perceptron(MLP). In this study, two inverter data which started operation at different day was used. A Multilayer Perceptron model was made to predict photovoltaic power data of the latest inverter. As a result of the model's performance test, the Mean Absolute Percentage Error(MAPE) was 4.1034. The verified model was applied to one-year-old and two-year-old data after old inverter starting operation. The predictive power of one-year-old inverter was larger than the observed power by 724.9243 on average. And two-year-old inverter's predictive value was larger than the observed power by 836.4616 on average. The prediction error of two-year-old inverter rose 111.5572 on a year. This error is 0.4% of the total capacity. It was proved that the error is meaningful difference by t-test. The error is predicted value minus actual value. Which means that PV system actually generated less than prediction. Therefore, increasing error is decreasing conversion efficiency of inverter. Finally, conversion efficiency of the inverter decreased by 0.4% over a year using this model.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.330-334
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• 2000

This paper proposes a new double-connected 3-phase voltage source inverter with improved output voltage waveform. An auxiliary single-phase inverter injects a ripple voltage into the double- connected inverter to convert 12-step operation to 36-step operation. The KVA rating of the output phase-shifting transformer is reduced by employing a harmonic canceling reactor. The whole rectifier-inverter system including the proposed technique is introduced and the experimental results are provided.