• Transactions on Electrical and Electronic Materials
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• 제18권4호
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• pp.190-194
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• 2017

Present-day solar panels incorporate inverters as their core components. Switching devices driven by specialized power controllers are operated in a transformerless inverter topology. However, some challenges associated with this configuration include the absence of isolation, causing leakage currents to flow through various components toward ground. This inevitably causes power losses, often being also the primary reason for the power inverters' analog equipment failure. In this paper, various aspects of the leakage currents are studied using different circuit analysis methods. The primary objective is to convert the leakage current energy into a usable DC voltage source. The research is focused on harvesting the leakage currents for producing circa 1.1 V, derived from recently developed rectifier circuits, and driving a $200{\Omega}$ load with a power in the milliwatt range. Even though the output voltage level is low, the harvested power could be used for charging small batteries or capacitors, even driving light loads.

• Journal of Power Electronics
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• 제10권4호
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• pp.374-381
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• 2010

Typical power electronic converters employ only pulse width modulation (PWM) to generate specific switching patterns. In this paper, a novel control strategy combining both pulse-width and amplitude modulation strategies (PWAM) has been proposed for power converters. The Pulse Amplitude Modulation (PAM), used in communication systems, has been applied to power electronic converters. This increases the degrees of freedom in eliminating or mitigating harmonics when compared to the conventional PWM strategies. The role of PAM in the novel PWAM strategy is based on the control of the converter's dc sources values. Software implementation of the conventional PWM and the PWAM control strategies has been applied to a five-level inverter for mitigating selective harmonics. Results show the superiority of the proposed strategy from the THD point of view along with a reduction in the inverter power dissipation.

• Proceedings of the KIPE Conference
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.593-597
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• 2003

Multilevel power conversion technology has received increasing attention recently for high power applications. The converters with the technology are suitable for high voltage and high power applications due to their ability to synthesize waveforms with better harmonic spectrum and apply for the high voltage equipment with a limited voltage rating of device. In the family of multilevel inverters, the topologies based on cascaded H-bridges are particularly attractive because of their modularity and simplicity of control. This paper presents multilevel inverter with cascaded H-bridge for large-power motor drives. The main features of this drive 1) reduce harmonic injection 2) can generate near-sinusoidal voltages, 3) have almost no common-mode voltage; 4) are low dv/dt at output voltage; 5)do not generate significant over-voltage on motor terminal; The topology of the developed product is presented and the feasibility study of the inverter on 3300v 1MVA 7-level H-bridge type was tarried out with experiments.

• Journal of Power Electronics
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• 제16권2호
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• pp.654-665
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• 2016

The pumping of electric power from photovoltaic (PV) farms is normally carried out using transformers, which require heavy mounting structures and are thus costly, less efficient, and bulky. Therefore, transformerless schemes are developed for the injection of power into the grid. Compared with the H4 inverter topology, the H6 topology is a better choice for pumping PV power into the grid because of the reduced common mode current. This paper presents how the perturb and observe (P&O) algorithm for maximum power point tracking (MPPT) can be implemented in the H6 inverter topology along with the improved sinusoidal current injected to the grid at unity power factor with the average current mode control technique. On the basis of the P&O MPPT algorithm, a power reference for the present insolation level is first calculated. Maintaining this power reference and referring to the AC sine wave of bus bars, a sinusoidal current at unity power factor is injected to the grid. The proportional integral (PI) controller and fuzzy logic controller (FLC) are designed and implemented. The FLC outperforms the PI controller in terms of conversion efficiency and injected power quality. A simulation in the MATLAB/SIMULINK environment is carried out. An experimental prototype is built to validate the proposed idea. The dynamic and steady-state performances of the FLC controller are found to be better than those of the PI controller. The results are presented in this paper.

• The Transactions of the Korean Institute of Power Electronics
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• 제3권4호
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• pp.365-374
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• 1998

The SHE(Selected Harmonic Elimination) PWM scheme which eliminates specific lower order harmonics can generate h high quality output waveforms in 3-level PWM inverters. However. its application has limited since SHE switching a angles cannot be calculated on-line by a microprocessor-implemented control system. Based on off-line optimization. in which multiple SHE solutions were found and analysed for 2 to 5 switching angles per quarter in the 3-level SHE PWM pattern. this paper presents an algebraic algorithm for an ordinary microprocessor to calculate approximate SHE S switching angles on-line with such high resolution that it makes no practical difference between the accurate and the a approximate SHE switching angles. By employing the variable of the dc-link voltage Vdc' the proposed SHE PWM p pattern can ideally compensate the dc input fluctuation together with selected harmonics eliminated.

• Proceedings of the KIEE Conference
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.962-964
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• 2001

In this paper, the RC filter for mitigating the output overvoltage of the 3-level 3300V 4MW inverter is described. The descriptions on power circuit and overvoltage phenomena are presented. The output transformer which may be used to obtain the higher output voltage, makes the filter design difficult because the parameter measurements are not easy and the accuracy may be poor. So, this paper presents several preliminary results on the output overvoltage with or without transformer to investigate the overall system characteristics. Some experimental results are also provided when the designed filter is applied.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.17.2-17.2
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• 2010

Printed electronics is an emerging technology to realize various microelectronic devices via a cost-effective method. Here we demonstrated a high performance of p-channel and n-channel top-gate/bottom contact polymer field-effect transistors (FETs), and applications to elementary organic complementary inverter and ring oscillator circuits by inkjet processing. We could obtained high field-effect mobility more than $0.4\;cm^2/Vs$ for both of p-channel and n-channel FETs, and successfully measured inkjet-printed polymer inverters. The performance of devices highly depends on the selection of dielectrics, printing condition and device architecture. Optimized CMOS ring oscillators with p-type and n-type polymer transistors showed as high as 50 kHz operation frequency. This research was financially supported by development of next generation RFID technology for item level applications (2008-F052-01) funded by the ministry of knowledge economy (MKE).

• KIEE International Transactions on Power Engineering
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• 제4A권2호
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• pp.51-57
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• 2004

This paper describes the dynamic performance of a variable speed wind turbine system responding to a wide variety of wind variations. Modeling of the wind generation using power electronics interface is proposed for dynamic simulation analysis. Component models and equations are addressed and their incorporations into a transient analysis program, PSCAD/EMTDC are provided. A wind model of four components is described, which enables observing dynamic behaviors of the wind turbine resulting from wind variations. Controllable power inverter strategies are intended for capturing the maximum power under variable speed operation and maintaining reactive power generation at a pre-determined level for constant power factor control or voltage regulation control. The components and control schemes are modeled by user-defined functions. Simulation case studies provide variable speed wind generator dynamic performance for changes in wind speed

• Proceedings of the KIPE Conference
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.476-477
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• 2012

단상 풀브릿지 인버터는 직류전원에서 가변 주파수 전압을 발생시키는 전력변환기다. 또한 이를 근본으로 많은 곳의 산업현장에 응용되며 실제 가정생활이나 신재생 에너지의 변환 장치로 많이 사용된다. 또한 많은 MCU의 발달로 인해 PWM변조 방식의 인버터가 개발되는 상황이다. 이러한 경우 기존의 단상 풀 브릿지 인버터의 THD는 3-LEVEL로 THD의 특성 개선의 한계가 있는 것이 현재의 상황이다. 본 논문에서는 단상 풀브릿지의 인버터를 기본으로 개선된 토폴로지를 구현하여 THD의 특성을 한 단계 높인 방법을 제안하고자 한다.

• Journal of Power Electronics
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• 제18권4호
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• pp.1051-1066
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• 2018

This study presents a novel step-up switched capacitor multilevel inverter (SCMLI) structure. The proposed structure comprises 2 unequal DC voltage sources, 4 capacitors, and 14 unidirectional power switches. It can synthesize 21 output voltage levels. The important features of the proposed topology are its self-voltage boosting and inherent capacitor voltage balancing capabilities. Furthermore, a cascaded structure of the proposed SCMLI with an asymmetric DC voltage source configuration is presented. The proposed topology and its cascaded structure are compared with conventional and other recently developed topologies in terms of different aspects, such as the required components to produce a specific number of output voltage levels, the total standing voltage (TSV) and peak inverse voltage of the structure, and the maximum number of switches in the conducting path. Furthermore, a cost function is developed to verify the cost-effectiveness of the proposed topology with respect to other topologies. The TSV of the proposed topology is significantly lower than those of other topologies. Moreover, the developed topology is cost-effective compared with other topologies. A detailed operating principle, power loss analysis, and selection procedure for switched capacitors are presented for the proposed SCMLI structure. Extensive simulation and experimental studies of a 21-level inverter structure prove the effectiveness and merits of the proposed SCMLI.