• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.8
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• pp.2968-2974
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• 2010

Nowadays, the PV systems have been focused on the grid connection between the power source and the grid. The PV inverter can be considered as the core of the whole system because of an important role in the grid-interfacing operation. An important issue in the inverter control is the load current regulation. In the literature, Proportional Integral (PI) controller, which is normally used in the current-controlled Voltage Source Inverter (VSI), cannot be a satisfactory controller for an AC system because of the steady-sate error and the poor disturbance rejection, especially in high-frequency range. Compared with conventional PI controller, Proportional Resonant (PR) controller can introduce an infinite gain at the fundamental frequency of the AC source; hence it can achieve the zero steady-state error without requiring the complex transformation and the de-coupling technique. Theoretical analyses of both PI and PR controller are presented and verified by simulation and experiment. Both controller are implemented in a 32-bit fixed-point TMS320F2812 DSP processor and evaluated on a 3kW experimental prototype PV Power Conditioning System (PCS). Simulation and experimental results are shown to verify the controller performances.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.1961-1963
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• 1997

A new higher reaching speed algorithm for the position control systems of the treveling wave type Ultrasonic Motors(USM) is presented. As the frictional forces of the stator materials revolves the rotor, the temperature of the contact surfaces is increased. It deteriorates the performance of control system so that the control frequency of inverter deviate from the natural resonant frequence of USM during the normal operation. In order to get higher reaching speed in the position control, we propose a novel algorithm that detect the resonant frequency of USM using the simple hardware and decision Processing. The effectiveness of proposed algorithm is verified by the experimental results.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.233-235
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• 2005

Non-contact power supply (NCPS), as a clean and safe energy supply concept has been applying wildly. Comparing with the conventional transformer the non-contact transformer has a large air gap between the long primary winding and the secondary winding. Due to it, the non-contact transformer has increased leakage inductance and reduced magnetizing inductance. So the high frequency series resonant converter has been widly used on the non-contact power supply system for transferring the primary power to the secondary one, from what a high influence voltage can be gained on the secondry coil even though the large air gap exists. However, it still has the disadvantages of the load sensitive voltage gain characteristics when load is changing. In this paper, we propose a fuzzy logic controller to adjust the frequency of the inverter to track the resonat which is changing when the load is change.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.199-202
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• 2004

CCFL(Cold Cathode Fluorescent Lamp) are used to backlight of LCD(Liquid Crystal Display). This paper presents analysis of half-bridge type resonant inverter of CCFL drive in order to stable characteristics, and fluorescent lamp operation frequency is higher than resonant frequency for safe operation. Besides, The Piezoelectric ceramic transformer (PZT) is electro-mechanical device that transfers electrical energy through a mechanical vibration. The modified equivalent circuit model of the PZT considering the operating current level is derived to design the CCFL. The validity of this study was confirmed from the simulation and experiential result.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1136-1141
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• 1992

This paper proposes a control technique to obtain high frequency quasi sinusoidal DC-Link waveform permitting zero-voltage-switching(ZVS). This operation results in reduction of commutation stress and switching losses in the power devices because they cause no switching loss in principle. But in existing control methods, the resonant capacitor voltage is not frequently made of zero-cross oscillation. We propose an optimum control stratege which can sustain oscillation and keep the capacitor voltage at an allowable level. Some experimental results are included to confirm the validity of the analytical results.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1029-1031
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• 1992

This paper discussed the operational principles and characteristics of Voltage-Resonant Type DC-DC Converter of HF-Bridge Inverter Switching Control using A-SCR as switching elements. The characteristics of DC/DC Converter circuits were analyzed using the diagrams of design circuits and dimensionless control variables.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.2
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• pp.80-84
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• 2008

In this paper, we have posed contactless power supply method using the contactless transformer with multiple primary winding. Also, the system uses resonant frequency tracking method for safe power supply at the elevator's car. The proposed system has been verified by the simulation using ICA4 and Maxwell. The contactless power transmission system is designed for 5[kW] rate.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1082-1084
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• 2001

This paper presents a design techniques for an electronic ballast of HID lamps. An electronic ballast for HID lamps usually employs a high frequency resonant inverter and voltage-to-frequency converter to control the output and a half-bridge and series resonant circuit are chosen for the ballast. In this paper, the new lighting method for the stable ignition regardless of lamp types is designed. And this type of ballast has some useful functions such as surge protection, thermal protection, and dimmable function. Moreover the powerline communication skill is also used to transmit a dimming control signal.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2798-2800
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• 1999

A new circuit, modified valley fill (MVF) combined with resonant inductor of the self-excited resonant inverter and charge pump capacitors(CPCs), is presented to achieve high PF electronic ballast providing sufficient preheat current to lamp filaments for soft start maintaining low DC bus voltage. The MVF can adjust the valley voltage higher than half the peak line voltage. The CPCs draw the current from the input line to make up the current waveform during the valley interval. The measured PF and THD are 0.99 and 12%, respectively. The lamp current CF is also acceptable in the proposed circuit. The proposed circuit is suitable for implementing cost-effective electronic ballast.

• Journal of Power Electronics
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• v.11 no.4
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• pp.551-560
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• 2011

This paper proposes a grid-tied power conditioning system for the fuel cell power generation, which consists of a 2-stage DC-DC converter and a 3-phase PWM inverter. The 2-stage DC-DC converter boosts the fuel cell stack voltage of 26-48V up to 400V, using a hard-switching boost converter and a high-frequency unregulated LLC resonant converter. The operation of the proposed power conditioning system was verified through simulations with PSCAD/EMTDC software. Based on the simulation results, a laboratory experimental set-up was built with a 1.2kW PEM fuel-cell stack to verify the feasibility of hardware implementation. The developed power conditioning system shows a high efficiency of 91%, which is a very positive result for the commercialization.