• Proceedings of the KIPE Conference
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• 1997.07a
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• pp.314-317
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• 1997

The purpose of this study is developing a converter which is able to convert a 300[KW] power, and is a DC power supply output a 1500[V] DC voltage for inverter driving. The power converter is driven by two converter serisely and keep a high power factor of power source. This system is haven all the characteristic of voltage source converter by having a processing ability of regenerating power. The two converters controls a PWM modulation and output voltage using a only one 16 bit DSP processor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.153-156
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• 2001

Maximum Power Point Tracking(MPPT) is used in wind power generation systems to maximize wind power turbin output power, irrespective of wind speed conditions and of the load electrical characteristics. In this paper we do the equivalent modeling the mechanical energy of wind power turbine according to wind speed into the synchronous generator. We analyse the equivalent modeling output part of rectifier into DC/DC converter input part theoretically. We design a control algorithm for variable voltage according to wind speed intensity and density so that load voltage of chopper is controlled steadily using the maximum power point tracking (MPPT) control method. We analyse a battery charging characteristics and a charging circuit for power storage enabling the supply of stable power to the load. We design a system and do the modeling of it analytically so that it supplies a stable power to the load by constructing a DC-AC inverter point. Also we design a charging circuit usable in actual wind power generation system of 30kW and confirm its validity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.153-156
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• 2001

Maximum Power Point Tracking(MPPT) Is used in wind power generation systems to maximize wind power turbin output power, irrespective of wind speed conditions and of the load electrical characteristics. In this paper we do the equivalent modeling the mechanical energy of wind power turbine according to wind speed into the synchronous generator. We analyse the equivalent modeling output part of rectifier into DC/DC converter input part theoretically. We design a control algorithm for variable voltage according to wind speed intensity and density so that load voltage of chopper is controlled steadily using the maximum power point tracking(MPPT) control method. We analyse a battery charging characteristics and a charging circuit for power storage enabling the supply of stable power to the load. We design a system and do the modeling of it analytically so that it supplies a stable power to the load by constructing a DC-AC inverter point. Also we design a charging circuit usable in actual wind power generation system of 30kW and confirm its validity.

• Journal of Power System Engineering
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• v.8 no.1
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• pp.62-68
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• 2004

This paper describes a fault tolerant control in distributed PLC(Programmable Logic Controller) system to ensure reliability of controllers which have some faults simultaneously. First, the behavior of PLC is modeled as discrete expressions using Galois field. Then, we design the control laws for additional spare controllers to generate parity code with two dimensions. Finally, the algorithm for estimating normal output instead of abnormal output from the controllers with fault is suggested. Comparing to the traditional duplication method, the suggested method can reduce the number of spare controllers significantly to ensure control reliability. This method will be applied to an automatic system in order to increase reliability. Also, it can improve cost performance of the system.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1813-1820
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• 2016

Dual-mode photovoltaic power system should be capable of operating in grid-connected (GC) and stand-alone (SA) modes for distributed generation. Under different working modes, the optimal parameters of inverter output filters vary. Inverters commonly operate in GC mode, and thus, a small capacitance is beneficial to the GC topology for achieving a reasonable compromise. A predictive current control scheme is proposed to control the grid current in GC mode and thereby obtain high-performance power. As filter are not optimal under SA mode, a compound control strategy consisting of predictive current control, instantaneous voltage control, and repetitive control is proposed to achieve low total harmonic distortion and improve the output voltage spectrum. The seamless transfer between GC mode and SA mode is illustrated in detail. Finally, the simulation and experimental results of a 4 kVA prototype demonstrate the effectiveness of the proposed control strategy.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.87-90
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• 2003

There are generally two temperature control methods using ac voltage regulators - the phase control method and the on-off control method. The phase control method uses thyristor's angles of extinction for the output power regulation and the on-off control method uses the control of on and off times for the output power regulation. Both of methods have the problems that are the unbalance of the three phase and surge current caused system's destruction. The main object of this study proposes a solution of problems of surge currents and unbalance of three phase when thyristor voltage regulator is switching. To solve the problem, It is proposes that the solution of surge currents is using a tap transformer and an additional switch with adjustable resistance and applies zero crossing of switching voltage of two input line to power load. This method is discuss and verified by computer simulations and experiments.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.173-174
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• 2015

If a wind speed decreases during inertial control of a wind turbine generator (WTG), the rotor speed might decrease below the minimum operating limit, which is called over-deceleration (OD). When OD occurs, inertial control should be disabled and then the output power of a WTG significantly decreases. This significant power reduction causes a subsequent frequency drop. This paper proposes the stepwise inertial control to prevent OD when a wind speed decreases during inertial control. To do this, the proposed scheme changes the additional power output based on the rotor speed. The performance of the proposed scheme is investigated using an EMTP-RV simulator. The results show that the proposed inertial control scheme prevent OD even when the wind speed decreases during inertial control.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2315-2326
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• 2016

This paper discusses the elimination of DC voltage deviation and the enhancement of load current sharing accuracy in multi-terminal high voltage direct current (MT-HVDC) systems. In order to minimize the power line losses in different parallel network topologies and to insure the stable operation of systems, a decentralized control method based on a modified droop control is presented in this paper. Averaging the DC output voltage and averaging the output current of two neighboring converters are employed to reduce the congestion of the communication network in a control system, and the decentralized control method is implemented. By minimizing the power loss of the cable, the optimal load current sharing proportion is derived in order to achieve rational current sharing among different converters. The validity of the proposed method using a low bandwidth communication (LBC) network for different topologies is verified. The influence of the parameters of the power cable on the control system stability is analyzed in detail. Finally, transient response simulations and experiments are performed to demonstrate the feasibility of the proposed control strategy for a MT-HVDC system.

• Journal of Power Electronics
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• v.15 no.2
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• pp.399-410
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• 2015

A 6.5 V/50 kA high-frequency switching power supply (HSPS) system composed of 10 power modules is developed to meet the requirements of copper-foil electrolysis. The power module is composed of a two-leg pulse width modulation (PWM) rectifier and a DC/DC converter. The DC/DC converter adopts two full-wave rectifiers in parallel to enhance the output. For the two-leg PWM rectifier, the ripple of the DC-link voltage is derived. A composite control method with a ripple filter is then proposed to effectively improve the performance of the rectifier. To meet the process demand of copper-foil electrolysis, the virtual impedance-based current-sharing control method with load current full feedforward is proposed for n-parallel DC/DC converters. The roles of load current feedforward and virtual impedance are analyzed, and the current-sharing control model of the HSPS system is derived. Virtual impedance is used to adjust the current-sharing impedance without changing the equivalent output impedance, which can effectively reduce current-sharing errors. Finally, simulation and experimental results verify the structure and control method.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.322-326
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• 1989

This paper describes design procedure of suboptimal control to minimize a performance index which is represented as sum of square output error and the heat input power in arc welding process. Heat input and temperature of a fixed point on the surface of the material are concerned as input and output of the process, repectively. The suboptimal control law considered here in is a proportional plus integral type and is implemented by using only the output variables available from sensor which is also optimally located in a fixed point w.r.t. a moving weld touch.