• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.7
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• pp.343-350
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• 2005

Conventionally, for transferring the primary power to the secondary one, the high frequency series resonant converter has been widely used for the contactless power supply system. However, the high frequency series resonant converter has the disadvantages such as the low efficiency, the high voltage gain characteristics and deviation of the phase angle in the overall load range. To improve this disadvantages, In this paper, the characteristics of the high efficiency and unit voltage gain as well as in-phase are revealed in the proposed three-level LCLC (Inductor-Capacitor- Inductor-Capacitor) resonant converter. The results are verified on the simulation based on the theoretical analysis and the 4kW experimental Prototype.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.128-130
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• 2006

We introduce 2[MVA] 3300[V] 7-level voltage source inverter system developed by POSCON and describe the main characteristics of inverter system i.e. PWM converter, H-bridge power module, phase shifted carrier PWM The PWM converter is a three-phase boost converter, which operates in a 4-quadrant and in a nearly unit displacement power factor. Experimental waveforms are also presented to verify the proposed method and performance of the developed system.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.205-213
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• 2014

A wind generator (WG) maximum power point tracking (MPPT) system is presented here. It comprises of a variable-speed wind generator, a high-efficiency boost-type dc/dc converter and a control unit. The advantages of the aimed system are that it does not call for the knowledge of the wind speed or the optimal power characteristics and that it operates at a variable speed, thus providing high efficiency. The WG operates at variable speed and thus suffers lower stress on the shafts and gears compared to constant-speed systems. It results in a better exploitation of the available wind energy, especially in the low wind-speed range of 2.5-4.5 m/s. It does not depend on the WG wind and rotor-speed ratings or the dc/dc converter power rating. Higher reliability, lower complexity and cost, and less mechanical stress of the WG. It can be applied to battery-charging applications.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.86-92
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• 2009

This paper presents development of 6kw ZVS(Zero Voltage Switching) boost converter by 4-parallel operation. To realize a high capacity converter with 6 kw, 4-parallel operation of 1.5kW unit module is proposed in this paper. To meet high ratio input to output voltage, isolated type booster converter is designed. To achieve ZVS operation of 4-switches of full bridge and protect a voltage overshoot caused by switch turn-off, simple active-clamp circuit is applied to the primary side. For parallel operation of 4-modules, master-slave control method is proposed to achieve input current sharing of 4-unit converter modules accurately. For performance tests, simulation is carried out. Also, load and experimental tests of the developed booster converter, 230Vdc/6kW, are carried out under various conditions. For field tests, the developed converter is applied for boosting a battery power to high DC_link voltage for a VSI inverter which starts a micro-turbine(MT) installed in vehicle and it's performance is verified through high speed motoring a MT up to tens of thousands of rpm.

• International Journal of Railway
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• v.8 no.1
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• pp.10-14
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• 2015

Due to the characteristics of the vehicle structure, the magnetic levitation train has a confined bottom space thus a study on miniaturization and weight reduction of auxiliary power unit is essential. This auxiliary power unit is an essential device used for illumination, air conditioning, heating and air brake equipment excluding the motor. The previous auxiliary power unit for magnetic levitation train has used the hard switching having a high switching frequency with heavy loss in order to reduce the size of filter reactor and transformer but the reduction in volume was not significant. In this paper, by reducing the loss, reducing the size of the cooling unit and by increasing the switching frequency using the soft switching of resonant converter, it has miniaturized and reduced the weight of filter reactor and transformer which occupy significant space in the auxiliary power unit. This study has verified the performance of 50KVA grade prototype through simulated interpretation and analysis, and compared the size and weight of auxiliary power unit of the previous magnetic levitation train.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.11
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• pp.762-771
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• 1988

This paper presents the experimental study to confirm the basic properties extract the operating problems of SMES. A new fast control system including u-computer and 12pulse power converter are designed and fabricated. The experiment of 25KJ SMES discharge and charge is carried out by I-C (Inductor-Converter) unit using a new proposed control system. The proposed control algorithm is proved by the simulations and control properties tests. It is also confirmed experimetally that SMES connected I-C unit controlled by this control scheme has an effects on compansating freguency fluctuation by independent active power control.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.184-185
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• 2010

This paper deals with a ride-through technique of doubly-fed induction generator (DFIG) wind turbine systems using energy storage unit (ESU). By increasing the machine speed, some portion of the turbine power can be stored in the system inertia during grid faults. Also keeping the operation of rotor-side converter (RSC) and grid-side converter (GSC), the rotor current and DC-link voltage can be limited. The effectiveness of the proposed method is verified by simulation results for 2[MW] DFIG wind turbine system.

• Journal of Power Electronics
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• v.14 no.3
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• pp.572-579
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• 2014

As a non-linear time variant system, the four-quadrant line converter of an electric multiple unit (EMU) was expressed by linear time periodic functions near an operating point and modeled by a steady-state harmonic domain matrix. The components were then combined according to the circuit connection and relations of the feedback control loops to form a complete converter model. The proposed modeling method allows the study of the amplitude of harmonic impedances to explore harmonic coupling. Moreover, the proposed method helps provide a better design for the converter controllers, as well as solves the problem in coordination operation between the EMUs and the AC supply. On-site data from an actual $CRH_2$ high-speed train were used to validate the modeling principles presented in the paper.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.860-868
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• 2016

A bidirectional DC-DC converter (BDC) is an indispensable electrical unit for the electric vehicles (EVs). High efficiency, high power density, isolation, light weight and reliability are all essential requirements for BDC. In this paper, a 3 kW BDC for the battery charger of EVs is proposed. The proposed converter consists of a half-bridge structure on the primary side and an isolation transformer and a synchronous rectifier structure on the secondary side. With this topology, minimum number of switching devices are required for bidirectional power flow between the two dc buses of EVs. The easy implementation of the synchronous rectification gives advantages in terms of efficiency, cost and flexibility. The proposed BDC achieves high efficiency when operating in both modes (step-up and step-down). A 3 kW prototype is implemented to verify theoretical analysis and the performance of the proposed converter.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.2
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• pp.154-162
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• 2007

In this paper, we propose a new AC-DC converter control method to comply with harmonics regulation(IEC 61000-3) effective for the inverter system of an air conditioner whose power consumption is less than 2,500W. There are many different ways of AC-DC converter control, but this paper focuses on the converter control method that is adopting an input reactor with low cost silicon steel core to strengthen cost competitiveness of the manufacturer. The proposed control method controls input current every half cycle of the line frequency to get unit power factor and at the same time to reduce switching loss of devices and acoustic noise from reactor. This kind of converter is known as a Partial Switching Converter(PSC). In this study, theoretical analysis of the PSC has been performed using Matlab/Simulink while a 16-bit micro-processor based converter has been used to perform the experimental analysis. In the theoretical analysis, electrical circuit models and equations of the PSC are derived and simulated. In the experiments, micro-processor controls input current to keep the power factor above 0.95 by reducing the phase difference between input voltage and current and at the same time to maintain a reference DC-link voltage against voltage drop which depends on DC-link load. Therefore it becomes possible to comply with harmonic regulations while the power factor is maximized by optimizing the time of current flow through the input reactor for every half cycle of line frequency.