• Journal of Power Electronics
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• v.15 no.2
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• pp.555-566
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• 2015

A TRIAC dimming LED driver that can control the brightness of LED arrays for a wide range of source voltage variations is proposed in this paper. Unlike conventional PWM LED drivers, the proposed LED driver adopts a TRIAC switch, which inherently guarantees zero current switching and has been proven to be quite reliable over its long lifetime. Unlike previous TRIAC type LED drivers, the proposed LED driver is composed of an LC input filter and a variable switched capacitance, which is modulated by the TRIAC turn-on timing. Thus, the LED power regulation and dimming control, which are done by a volume resistor in the same way as the conventional TRIAC dimmers, can be simultaneously performed by the TRIAC control circuit. Because the proposed LED driver has high efficiency and a long lifetime with a high power factor (PF) and low total harmonic distortion (THD) characteristics, it is quite adequate for industrial lighting applications such as streets, factories, parking garages, and emergency stairs. A simple step-down capacitive power supply circuit composed of passive components only is also proposed, which is quite useful for providing DC power from an AC source without a bulky and heavy transformer. A prototype 60 W LED driver was implemented by the proposed design procedure and verified by simulation and experimental results, where the efficiency, PF, and THD are 92%, 0.94, and 6.3%, respectively. The LED power variation is well mitigated to below ${\pm}2%$ for 190 V < $V_s$ < 250 V by using the proposed simple control circuit.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1948_1949
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• 2009

All the power generating station require dc auxiliary power systems to operate those dc components that must be available if a loss of ac power occur. Some examples of such components are auxiliary motors, circuit breakers, relays and solenoids. The dc source may be one common battery for both power and control or two separate batteries; one for power and another for control. Typically, a dc auxiliary power system is designed as an ungrounded system, instead of grounded system, so that a low-resistance ground fault on one of its two polarities will not affect the operation of the system, thus increasing system reliability and continuity of service. A ground detector should provide a high polarity-to-ground resistance so that a single ground fault occurring on the system will not affect the operation of that system. Sensitive relays have been known to energize momentarily while the cable and capacitive charge to ground shifts[1]. A power station had experienced this kind of incident and performed root cause analysis based on PC based simulation program known as PSpice. This simulation showed adapted relays on the system energize momentarily and design criteria on this relay should be corrected.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1796-1801
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• 2008

In this paper, a new current based maximum power point tracking (CMPPT) method is proposed for a single phase photovoltaic power conditioning system and the current based MPPT modifies incremental conductance method. The current based MPPT method makes the entire control structure of the power conditioning system simple and uses an inherent current source characteristic of solar cell array. In addition, digital phase locked loop using an all pass filter is introduced to detect phase of grid voltage as well as peak voltage. Controllers about dc/dc boost converter, dc-link voltage, dc/ac inverter is designed for a coordinated operation. Furthermore, PI current control using a pseudo synchronous d-q transformation is employed for grid current control with unity power factor. 3kW prototype photovoltaic power conditioning system is built and its experimental results are given to verify the effectiveness of the proposed control schemes.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1169-1170
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• 2006

Grid connected PV(Photovoltic) generation systems are becoming and actual and general. The power output of PV system is directly affected by the weather conditions. And when AC power supply is needed, power conversion by an inverter and a MPPT control are necessary. The PV power generation system can be treated to a harmonics source for the power distribution system. So, the PV system combined the function of active filter system can be useful applied in power distribution system. AF(Active Filters) intended for harmonic solutions are expending their functions from harmonic compensation of nonlinear loads into harmonic isolation between utilities and consumer. With the test analysis of the proposed control strategy of PV-AF system, the outcome of the test shows the stability and effectiveness of the proposed PV-AF system. The various capability of AF has been proved in previous research and usage. In this paper, authors present a DSP controlled PV-AF system for power conditioning in three-phase industrial or commercial power systems and verify it through experimental results.

• Journal of Power Electronics
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• v.5 no.4
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• pp.289-304
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• 2005

This paper describes a simple control structure and power conditioning system for an indirect vector controlled stand-alone induction generator (IG) used to operate under variable speed. The required reactive power for the IG system is supplied by means of a capacitor bank and a voltage-source PWM converter. Using a capacitor bank to transfer the reactive power to the IG under the rated speed and no-load conditions starts the IG operation and reduces the PWM converter size. The vector control structure for the variable speed IG power conditioning system compensates for changes in the electrical three-phase and DC loads while considering the magnetizing curve of the IG. The vector control structure is developed to regulate the DC link voltage of the PWM converter and the IG output voltage. The experimental and simulated performance results of the IG power conditioning system at various speeds and loads are given and show that this proposed scheme can be used efficiently for a variable speed, wind energy conversion system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.755-761
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• 2017

In railways powered by AC power, the main circuit breaker (MCB) is used for supplying the electric power to the catenary of the vehicle. Generally, the main circuit breaker is located between the pantograph and the main transformer, and the phase of the power applied to the vehicle changes according to the operation timing of the main circuit breaker. The operation of the main circuit breaker should be actively controlled according to the phase of the power source, since the phase of the power causes unintended transient states in the vehicle's electrical system in the form of an inrush current and surge voltage. However, the MCB has a delay time when it operates which is not constant. Therefore, an intelligent controller is needed to predict the operation delay time and control the opening and closing of the MCB.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.13-14
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• 2011

The power conversion converter for driving the wireless power transfer system is can be into the two part of the DC power conversion rectifier and the high frequency dc-ac power conversion inverter. In this paper, The operating characteristics of the Class-${\Phi}_2$ resonant inverter have been investigated through by simulation and by experiment. It can be switched at a high frequency without the switching losses and the harmonics are reduced effectively due to the input LC filter. Its switching frequency is 1MHz and the input voltage is 96V which is the output voltage of LLC resonant converter. And its output peak voltage is 170V. The resonant inverter module operated at the commercial power source of 220V was built. And also the electromagnetic coupled resonance coils were designed for wireless power transfer with a 1MHz operating frequency. As a experimental result, the wireless power transmission was confirmed and it is varified the validity of the experiment.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.234-236
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• 2006

In this paper, APF(Active Power Filter) will be treated in order to improve the output current distortion of the AC source. APF generates the harmonic current which contributes to a source side harmonic reduction. We can extract the compensating current of the parallel APF with phase transformations and the proposed current control method. Therefore, the calculation times is short and the control method is simple compared with conventional hysteresis methods. Experimental results verify that the system using the proposed method appers a good performance.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.426-428
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• 1997

This paper presents the linearized optimal PWM techniques for current source GTO converter. This proposed method is to linearize an optimal PWM modulation strategy so that the turn-on/off-periods of the GTO switches can be computed on-line in real-time for any modulation index. This allows the rapid and continuous regulation of the DC output current while producing the sinusoidal AC input current waveform and unit power factor.

• Journal of the Optical Society of Korea
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• v.3 no.2
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• pp.80-85
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• 1999

We propose and demonstrate a new scheme for suppression of output distortion in an open-loop gyroscope employing an erbium-doped fiber amplifier/source (FAS). In addition to the main modulation for the rotation rate measurement, a small auxiliary modulation at a different frequency is used to extract an error signal, which is necessary for keeping the quasi-dc component of the feedback signal power at a constant level for varying rotation rate. By active tracking of the optimum modulation condition using this two-frequency modulation scheme, we obtain stable gyro output with suppressed distortion as well as stable FAS characteristics. We also calculate the distortion in the gyro response due to the feedback effect, from which we estimate the FAS gyro output distortion due to the residual ac feedback effect when the dc feedback effect is removed by the proposed scheme. The measured residual deviation agrees reasonably with the estimation.