• IEIE Transactions on Smart Processing and Computing
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• v.5 no.1
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• pp.35-42
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• 2016

Developments in power electronics have enabled the widespread application of Pulse Width Modulation (PWM) inverters, notably for connecting renewable systems to the grid. This study demonstrates that a high-quality power can be achieved using a stand-alone inverter, whereby the comparison between the power quality of the stand-alone inverter with battery storage (off-grid) and the power quality of the utility network is presented. Multi-loop control techniques for a single phase stand-alone inverter are used. A capacitor current control is used to give active damping and enhance the transient and steady state inverter performance. A capacitor current control is cheaper than the inductor current control, where a small current sensing resistor is used. The output voltage control is used to improve the system performance and also control the output voltage. The inner control loop uses a proportional gain current controller and the outer loop is implemented using internal model control proportional-integral-derivative to ensure stability. The optimal controls are achieved by using the Sisotool tool in MATLAB/Simulink. The outcome of the control scheme of the numerical model of the stand-alone inverter has a smooth and good dynamic performance, but also a strong robustness to load variations. The numerical model of the stand-alone inverter and its power quality are presented, and the power quality is shown to meet the IEEE 519-2014. Furthermore, the power quality of the off-grid system is measured experimentally and compared with the grid power, showing power quality of off-grid system to be better than that of the utility network.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.2
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• pp.241-249
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• 2017

Plasma membrane hyperpolarization associated with activation of $Ca^{2+}$-activated $K^+$ channels plays an important role in sperm capacitation during fertilization. Although Slo3 (slowpoke homologue 3), together with the auxiliary ${\gamma}^2$-subunit, LRRC52 (leucine-rich-repeat-containing 52), is known to mediate the pH-sensitive, sperm-specific $K^+$ current KSper in mice, the molecular identity of this channel in human sperm remains controversial. In this study, we tested the classical $BK_{Ca}$ activators, NS1619 and LDD175, on human Slo3, heterologously expressed in HEK293 cells together with its functional interacting ${\gamma}^2$ subunit, hLRRC52. As previously reported, Slo3 $K^+$ current was unaffected by iberiotoxin or 4-aminopyridine, but was inhibited by ~50% by 20 mM TEA. Extracellular alkalinization potentiated hSlo3 $K^+$ current, and internal alkalinization and $Ca^{2+}$ elevation induced a leftward shift its activation voltage. NS1619, which acts intracellularly to modulate hSlo1 gating, attenuated hSlo3 $K^+$ currents, whereas LDD175 increased this current and induced membrane potential hyperpolarization. LDD175-induced potentiation was not associated with a change in the half-activation voltage at different intracellular pHs (pH 7.3 and pH 8.0) in the absence of intracellular $Ca^{2+}$. In contrast, elevation of intracellular $Ca^{2+}$ dramatically enhanced the LDD175-induced leftward shift in the half-activation potential of hSlo3. Therefore, the mechanism of action does not involve pH-dependent modulation of hSlo3 gating; instead, LDD175 may modulate $Ca^{2+}$-dependent activation of hSlo3. Thus, LDD175 potentially activates native KSper and may induce membrane hyperpolarization-associated hyperactivation in human sperm.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.1
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• pp.57-65
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• 2001

The speed control without a speed sensor is expected strongly to progress reliability, simplicity and cost performance of Induction Motor(I.M) systems. Also, it contributes to expansion of I.M systems into various industrial application fields. This paper investigates a novel speed sensorless control method of I.M considering the secondary resistance identification based on the transientless torque control technique. Especially, this paper aimed at the identification of the secondary resistance simultaneously with speed estimation superposing of sinusoidal flux wave to a constant flux value. Furthermore, the secondary flux with some frequency is controlled independently on torque control. The proposed speed estimation method is derived from a motor circuit equation theoretically and also it can be conducted easily by detecting primary motor currents and primary voltage commands at every sampling time. Some numerical simulations with the assumption of using a pulse width modulation(PWM) voltage source inverter are performed to verify the proposed method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.105-112
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• 2003

Diode rectifier which can't be controlled output voltage and phase control converter as AC/DC converter have low power factor and harmonics of lower order in the line current. In this paper, three phase PWM(Pulse Width Modulation) AC/DC boost converter is studied to solve these problems. The characteristics of a proposed converter are to control the phase of current without current sensor as a very simple control algorithm using circuit parameters only and to apply sinusoidal PWM method with fixed switching frequency due to a difficult design of input filter and switching device. We simulate for the proposed algorithm that high power factor is achieved and DC link voltage has fast dynamic response without ripple in rectifying and regenerating operation. As a result of experiment with circuit parameter(inductor, capacitor) decided in simulation, the proposed converter had high power factor and reduction of low order harmonics as against diode rectifier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.351-358
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• 2013

We propose a correction method of nonlinear frequency sweep in an FMCW(Frequency Modulated Continuous Wave) laser range finder. FMCW laser range finder requires linear frequency sweep for high resolution, and nonlinear frequency sweep makes the system performance degrade. In general, VCO(Voltage Controlled Oscillator) which is a component used for frequency modulation in FMCW method has nonlinear property. To correct the nonlinear frequency sweep, we utilize an auxiliary delay structure for generating trigger signal of ADC(Analog to Digital Converter). Because the trigger signal has same rate of change with the beat signal, the nonlinearity of the beat signal can be corrected. the experimental results show that the proposed method effectively eliminates the nonlinear frequency sweep problem and enhances the system performance.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1540-1551
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• 2015

The detection of position and speed in BLDC motors without using position sensors has meant many efforts for the last decades. The aim of this paper is to develop a sensorless technique for detecting the position and speed of BLDC motors, and to overcome the drawbacks of position sensor-based methods by improving the performance of traditional approaches oriented to motor phase voltage sensing. The position and speed information is obtained by computing the derivative of the terminal phase voltages regarding to a virtual neutral point. For starting-up the motor and implementing the algorithms of the detection technique, a FPGA board with a real-time processor is used. Also, a versatile hardware has been developed for driving BLDC motors through pulse width modulation (PWM) signals. Delta and wye winding motors have been considered for evaluating the performance of the designed hardware and software, and tests with and without load are performed. Experimental results for validating the detection technique were attained in the range 5-1500 rpm and 5-150 rpm under no-load and full-load conditions, respectively. Specifically, speed and position square errors lower than 3 rpm and between 10º-30º were obtained without load. In addition, the speed and position errors after full-load tests were around 1 rpm and between 10º-15º, respectively. These results provide the evidence that the developed technique allows to detect the position and speed of BLDC motors with low accuracy errors at starting-up and over a wide speed range, and reduce the influence of noise in position sensing, which suggest that it can be satisfactorily used as a reliable alternative to position sensors in precision applications.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.38 no.5
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• pp.70-78
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• 2001

We have developed a novel driving system of 5' true color FED using voltage controlled PWM method which has current control effect. The proposed method has the advantage of voltage controlled pulse width modulation method and current control method. Also, we propose a new circuit model of FED subpixel for circuit simulation of FED driving circuits, considering some parasitic effects, i.e., cross talk, line coupling effect and leakage current to the adjacent cathode lines. Output stage of the data driving circuit is optimized using the proposed circuit model. In video data processing, FED controller uses the parallel processing of R.G.B input data, so duty ratio is maximized and brightness of FED increases. With this results, no noise and high quality performance is achieved in display of 5' true color FED.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.6
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• pp.472-480
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• 2009

This paper describes the overmodulative SVPWM technique and harmonics analyses of three phase NPC type three-level inverter to the modulation index. Three phase NPC type three-level inverter adopted SVPWM to extend the linear region to 0.907, moreover, the following voltage compensation using Fourier series was adopted in the region of overmodulation to make it work to six-step level. PD type of multi carrier method is used with the double Fourier series for the analysis of output power harmonics characteristic. Simulation was performed by PSIM, and the harmonics characteristics of 3-level inverter in each region are analyzed. The side band harmonics of carrier frequency are dominant in the linear region, but these harmonic components are decreased as the inveter goes to overmodulation region, and the harmonics due to the fundamental frequency is increased gradually at the same time. The harmonic analyses are verified through the simulation and experimental results under the same condition.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.38-43
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• 2003

Fabrication process of strain-induced channel waveguides in $LiNbO_3$ was developed using strain-optic effect and compressional strain due to ~1.4 $\mu\textrm{m}$ surface Mo/Pt metal film. Characterization of the channel waveguides revealed a single transverse and depth mode in both TE and TM polarizations. Measurements showed total insertion loss of 6.2 and 7.7 ㏈/cm for TM and TE polarizations. respectively. Electro-optic intensity modulators with 11 mm long electrode length and 21 $\mu\textrm{m}$ electrode gap at $\lambda$ = 1.15 ${\mu}{\textrm}{m}$have been produced in $LiNbO_3$ substrates using strain-induced channel waveguides. Modulation depth of 100% at $\pi$-radian voltage of 16.1V has been demonstrated. Also, 1$\times$2 on/off power splitters at $\lambda$ = 0.63 $\mu\textrm{m}$ have been produced using strain-induced channel waveguides. On/off voltage of $\pm$ 25V has been demonstrated.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.386-393
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• 2000

This paper presents an improved ZVS partial series resonant DC/DC converter (PSRC) with low conduction losses, suitable for high power and high frequency applications. The proposed PSRC have advantages of zero-voltage-switching (ZVS) of main switches for entire load ranges low conduction losses of main switches by decreasing current stresses. Also the reduction of the effective duty cycle is not occurred during the resonant period of the main circuit because the auxiliary circuit of the proposed converter is placed out of the main power path. The auxiliary circuit is composed with passive components, which are an inductor, two capacitors, two diodes, and a saturable inductor. An improved ZVS PSRC has so much characteristics with respect to the overall system efficiency and to the reduction of current stresses. The operation principles of the proposed converter are explained in detail and the various simulated and experimental results show the validity of the proposed converter.