• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1976-1977
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• 2007

This paper introduce the electrical quantities of a three-phase-connected wind induction generator (WIG) under sudden connection of static loads. An intelligent power-system recorder/monitor is employed to measure threephase voltages and currents of the studied system at WIG's terminals and load's terminals for 5 minutes. A laboratory 300 W wound-rotor induction machine driven by a blushless DC motor is utilized as the studied WIG. Since the generated harmonic currents are randomly varied, total harmonic distortion (THD) of current using cumulative probability density function is employed to determine the penetration of harmonic distortion. The results show that the harmonic currents generated by the studied WIG may be severely amplified to a high level by the connected self-excited capacitance at the stator's terminals.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.206-208
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• 1995

Recently according to the increasing critical loads such as communication and life support systems stable power supplying becomes more and more important. Therefore it is indespensable to stabilize power source using these instruments - AVR(Automatic Voltage Regulator) or UPS(Uninterrutible Power Supply). This paper deals with ON-LNE UPS which is composed of PWM converter for AC-DC conversion. Using a PWM converter have advantages of low current harmonics and high power factor. In this paper ON-LNE UPS using PWM converter is proposed and its characteristics are investigated.

• Journal of Power Electronics
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• v.17 no.4
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• pp.983-990
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• 2017

This paper proposes a model predictive control based on the discrete Lyapunov function to improve the performance of power electronic converters. The proposed control technique, based on the finite control set model predictive control (FCS-MPC), defines a cost function for the control law which is determined under the Lyapunov stability theorem with a control error compensation. The steady state and dynamic performance of the proposed control strategy has been tested under a single phase AC/DC voltage source rectifier (S-VSR). Experimental results demonstrate that the proposed control strategy not only offers global stability and good robustness but also leads to a high quality sinusoidal current with a reasonably low total harmonic distortion (THD) and a fast dynamic response under linear loads.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.66.1-66
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• 2001

As choosing proper length of boom of container crane according as sort of vessels(18, 22, 24 columns and so on), reinforcing of capacity of DC motor to transport heavy loads, it´s structure being oversized with flexibility and durability, the study is progressing on the automation for convenient operation and effective control. We often cannot but work slowly caused by swaying(pitching, rolling) of vessel. We can get productivity and efficiency by getting over it. The factors of swaying, as fellow; - wave caused by vessels around moving - wind and wave caused by weather change - vessel´s moving by change of load weight - tide - move of vessel According to ...

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.817-825
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• 2017

The AC-common bus microgrid system can overcome several weaknesses of the DC microgrid system by interconnecting the DC/AC inverters used for renewable energy with an AC network. Nevertheless, the unbalanced loads inherent in the electric power systems of island and small communities can deteriorate the performance of the AC microgrid system. This is because of the limited voltage regulation capability and mixed power flow in the voltage source inverter. In order to overcome the unbalanced load condition, this paper proposes a voltage and current control algorithm for the 4-leg inverter based on the single phase d-q control method, as well as the modeling of the voltage controller using Matlab/Simulink S/W. From the S/W simulation and experiment of the 250KW proto-type inverter, it is confirmed that the proposed algorithm is a useful tool for the design and operation of the AC microgrid system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.587-592
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• 2018

Because the brightness of an AMOLED is determined by the flowing current, each pixel of AMOLED operates via A current driving method. Therefore, it is necessary to supply power to adjust the amount of current according to THE user's requirement for AMOLED driving. In this study, an IP driver block was designed and a simulation was conducted for an AMOLED display, which supplies power as selected by users. The IP driver design focused on regulating the output power due to the OLED characteristics for the diode electric current according to the voltage to be activated by pulse-skipping mode (PSM) under low loads, and 1.5 MHz pulse-width modulation (PWM) for medium/high loads. The IP driver was designed to eliminate the ringing effects appearing from the dis-continue mode (DCM) of the step-up converter. The ringing effects destroy the power switch within the IC, or increase the EMI to the surrounding elements. The IP driver design minimized this through a ringing killer circuit. Mobile applications were considered to enable true shut-down capability by designing the standby current to fall below $1{\mu}A$ to disable it. The driver proposed in this paper can be applied effectively to the same system as the AMOLED display dual power management circuit.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.159-179
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• 2022

Often a network becomes complex, and multiple entities would get in charge of managing part of the whole network. An example is a utility grid. While the entire grid would go under a single utility company's responsibility, the network is often split into multiple subsections. Subsequently, each subsection would be given as the responsibility area to the corresponding sub-organization in the utility company. The issue of how to make subsystems of adequate size and minimum number of interconnections between subsystems becomes more critical, especially in real-time simulations. Because the computation capability limit of a single computation unit, regardless of whether it is a high-speed conventional CPU core or an FPGA computational engine, it comes with a maximum limit that can be completed within a given amount of execution time. The issue becomes worsened in real time simulation, in which the computation needs to be in precise synchronization with the real-world clock. When the subject of the computation allows for a longer execution time, i.e., a larger time step size, a larger portion of the network can be put on a computation unit. This translates into a larger margin of the difference between the worst and the best. In other words, even though the worst (or the largest) computational burden is orders of magnitude larger than the best (or the smallest) computational burden, all the necessary computation can still be completed within the given amount of time. However, the requirement of real-time makes the margin much smaller. In other words, the difference between the worst and the best should be as small as possible in order to ensure the even distribution of the computational load. Besides, data exchange/communication is essential in parallel computation, affecting the overall performance. However, the exchange of data takes time. Therefore, the corresponding consideration needs to be with the computational load distribution among multiple calculation units. If it turns out in a satisfactory way, such distribution will raise the possibility of completing the necessary computation in a given amount of time, which might come down in the level of microsecond order. This paper presents an effective way to split a given electrical network, according to multiple criteria, for the purpose of distributing the entire computational load into a set of even (or close to even) sized computational loads. Based on the proposed system splitting method, heavy computation burdens of large-scale electrical networks can be distributed to multiple calculation units, such as an RTDS real time simulator, achieving either more efficient usage of the calculation units, a reduction of the necessary size of the simulation time step, or both.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.4
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• pp.210-220
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• 2002

We analysised the effect of harmonics on electric machines of substation power system barred on quantitatively measured harmonics and proposed the methods for prevention of harmonics through checking on transformer, rectifier and cable's capacities against harmonics with reference to KEPCO's electricity service standard. In order to analysis harmoninics of silicon rectifier that is power source in DC substation, computer simulations for a substation with TR of high voltage distribution switchboard are performed. Simulation results show that the total harmonic distortion factor becomes smaller for TR primary and receiving points in order rather than silicon rectifier which is harmonic generation source so that the harmonics generated frets each rectifier are outflowed to power supply and high voltage distribution switchboard The result of higher distortion factors of voltage and current for rectifier with 100% load than those with 50 % and 30% indicates that the waveform of voltage and current for the real substation power system at the office-going and the closing hours with heavy loads might be more distorted. As proposed methods for harmonic reduction, the conventional 6 pulse-type for substation is required to be replaced by 12 pulse-type for reduction of 5th and 7th harmonics. The active filter rather than the passive filter is more effective due to severe variance of rectifier loads, but the high cost is price to be paid. In view of installation area and costs, the use of 12 pulse-type transformer is desirable and then the parallel transformer and the rectifier within the substation must be replaced at the same time. Other substations with parallel feeder can use 6 pulse-type transformer.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.584-591
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• 2000

Power Quality Compensator(PQC) has been installed to protect the sensitive loads against the voltage disturbances, such as voltage sag and interruption. In general, static switch is used for the purpose of link between utility and PQC. So transfer operation of the static switch play a important part in the PQC. Many studies on the structure and control of PQC have been progressed in active, but these researches have been rarely mentioned about any voltage-disturbances-detection method to start the PQC operation. In this paper, a new voltage-disturbances-detection algorithm for computer application loads using the CBEMA/ITIC curve is proposed for transfer operation of the static switch. The proposed detection algorithm is implemented to get fast detecting time through the comparison of instantaneous 3-phase voltage values transferred to DC values in the synchronous reference frame with the operating reference values. To get the robust characteristics against the noise, a first order digital filter is designed. The magnitude falling and phase delay caused by the filter are compensated through the error normalizing and numerical analysis using transfer function, respectively. Finally, the validity of the proposed algorithm is proved by ACSL simulation and experimental results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.4
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• pp.360-364
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• 2012

AC to DC converter that consists of relatively simple diode rectifier devices has been widely used in the field of the electric propulsion system. Also, since this rectifier includes large harmonics in the input current, a variety of researches have been developed to reduce the harmonics. The proposed method of this paper is to reduce the harmonics included in the input current of rectifiers and propulsion motor by injecting the output current of diode rectifier into the input of them. In addition, the proposed method ensures electrical safety through the respective isolation of the injection current, the source, and the loads using the Wye-Delta insulating transformer applied in current injection device that is installed in the input circuit of rectifiers and propulsion motor. The proposed method is simulated by applying to the electric propulsion ship that is currently operating. We confirm the validity of the proposed method compared with conventional power conversion system.