• Journal of Power Electronics
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• v.16 no.2
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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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• v.23 no.5
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• pp.328-335
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• 2018

An energy management method of DC microgrids using voltage compensation term is proposed in this study. Droop control is often implemented to operate the DC microgrid. However, the droop control necessarily generates voltage variation. Energy flow is also difficult to control because the droop control mainly focuses on proportional load sharing. To solve these problems, the voltage compensation term based on the low-bandwidth communication is used to determine the operating band of the converter. Energy management and voltage variation minimization can be achieved by judging the operating band according to the magnitude of voltage compensation term. The validity of the proposed method is verified by simulation and experiments.

• Journal of the Korea Society of Computer and Information
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• v.5 no.4
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• pp.62-68
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• 2000

It was designed a high-speed analog input card that is a important device of ultrasonic testing flaw detector in the middle of non-destructive testing in this Paper. The A/D Board is inquired high-speed sampling rate and fast data acquisition system. This pater shows a design that has a function of Peak- Detection for ultrasonic testing by ISA Bus type and a 50MHz of A/D converter in order to do sampling more than quadruple frequency of transducer frequency.

• Journal of Power Electronics
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• v.18 no.1
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• pp.56-69
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• 2018

In this paper, an improved Space Vector Modulation (SVM) based fault tolerant operation on a nine-level Cascaded H-Bridge (CHB) inverter with an additional backup circuit is proposed. Any type of fault in a power converter may result in a power interruption and productivity loss. Three different faults on H-bridge modules in all three phases based on the SVM approach are investigated with diagrams. Any fault in an inverter phase creates an unbalanced output voltage, which can lead to instability in the system. An additional auxiliary unit is connected in series to the three phase cascaded H-bridge circuit. With the help of this and the redundant switching states in SVM, the CHB inverter produces a balanced output with low harmonic distortion. This ensures high DC bus utilization under numerous fault conditions in three phases, which improves the system reliability. Simulation results are presented on three phase nine-level inverter with the automatic fault detection algorithm in the MATLAB/SIMULINK software tool, and experimental results are presented with DSP on five-level inverter to validate the practicality of the proposed SVM fault tolerance strategy on a CHB inverter with an auxiliary circuit.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.916-922
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• 2014

Diode rectifiers have been widely used for an AC to DC converter. But a big problem is that they include large harmonics components in the input currents. A 12-pulse configuration with phase shifting transformer is useful for reducing them. however, it still includes the ($12{\pm}1$)th (m; integer) harmonics in the input currents. In this paper, we propose a single-phase square wave auxiliary voltage supply which is inserted in the middle DC bus. It reduces harmonics especially the 11th and 13th and the harmonic characteristic becomes almost equivalent to a 24-pulse rectifier. Theoretical analysis of the combined 12-pulse diode rectifier with the auxiliary supply is presented and a control method of the auxiliary supply is proposed. The reduction in the input current harmonics is verified by simulation using software PSIM.

• The KIPS Transactions:PartA
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• v.15A no.6
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• pp.317-324
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• 2008

In this paper, we propose a system which easily controls the existing serially connected multi-channel speakers in a general personal computer by using a USB(Universal Serial Bus) interface. The personal computer as a host of the USB interface analyzes a sound source and sends audio data in a real-time fashion by the use of the isochronous transmission, one of four transmission methods provided by the USB interface. In addition, a channel is assigned by means of the bulk transmission, one of four transmission methods provided by the USB interface. Transmitted data from the USB host are sent to each speaker through compression and packet generation process. Each speaker detects corresponding digital data and regenerates audio signals through DAC(Digital-to-Analog Converter). A user can easily select a sound source file and a channel by the use of a GUI environment in a personal computer.