• Journal of Power Electronics
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• v.10 no.1
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• pp.91-96
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• 2010

In this paper, a simplified control algorithm for a three-phase, four-wire unified power quality conditioner (UPQC) is presented to compensate for supply voltage distortions/unbalance, supply current harmonics, the supply neutral current, the reactive power and the load unbalance as well as to maintain zero voltage regulation (ZVR) at the point of common coupling (PCC). The UPQC is realized by the integration of series and shunt active filters (AFs) sharing a common dc bus capacitor. The shunt AF is realized using a three-phase, four leg voltage source inverter (VSI) and the series AF is realized using a three-phase, three leg VSI. A dynamic model of the UPQC is developed in the MATLAB/SIMULINK environment and the simulation results demonstrating the power quality improvement in the system are presented for different supply and load conditions.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.275-278
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• 2003

Conventional vector control inverter is usually used for blower of air-accord equipment. In this paper, it is proposed that inverter is controlled by instantaneous following PWM controller. This controller compensate and follow for output voltage of inverter within one switching cycle as an error that compared output voltage of rectifier included much ripples with reference voltage of sine wave. It has not speedy response like vector controller, but the circuit is very simple as using analog integer. And it has advantages that develop input power factor, built small-capacity and low-cost because huge capacitor of voltage type inverter removed.

• Journal of Biosystems Engineering
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• v.22 no.3
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• pp.303-310
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• 1997

Motivated by the need fir developing the new method of weed control in place of chemical weedicide, this paper aims at making good use of electricity against environmental pollution. Compared with chemical weedicide, the electric method of weed control is functionally more versatile, effectively more rapid, and lower in terms of cost. In particular, this method will contribute to environmental protection. In detail the electrical weed control system which is the simple circuit for generating the electric current of high voltage is comprised of step-up transformer which rectifies the current and the capacitor which stores the energy. The effectiveness of electrical weed control system is evaluated by germination rate and control of Dgitaria Sangvinalis(Galinsoga ciliate). As a result, the electrical weed control system(high voltage spark discharge) can kill weeds effectively

• The Transactions of the Korean Institute of Electrical Engineers
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• v.34 no.8
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• pp.331-337
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• 1985

An inverter-excited induction generator is discussed in this paper. A brief review of the capacitor-excited induction generator is given and the steady state characteristics of the induction generator excited by an inverter are evaluated. It is shown that the output voltage of the system can be controlled by adjusting the slip, for given operating conditions. The introduction of feedback control makes it possible to control the output voltage stably over the wide range of speed and load. Experimental results are given. The output of the induction generator is then converted into a CVCF(Constant Voltage-Constant Frequency) power source using a PWM inverter with simple control circuit.

• Journal of Industrial Technology
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• v.19
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• pp.217-226
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• 1999

A single phase to three phase power converter with cost effective and simple structure is proposed. The converter consists of rectifier and inverter. The rectifier is composed of a half wave rectifier, a dc link capacitor, and a current limiting inductor, and the inverter is of only two switches with PWM control. For negative sequence operation the inverter output voltage leads the line input by $60^{\circ}$, and for positive sequence operation the inverter output voltage leads by $60^{\circ}$. We can see that positive sequence operation shows higher output voltage, slight harmonic distortion(2%), and better performances such as high efficiency and high power factor. A mathematical model for system analysis is provided, and specifications for selection and control scheme both for start-up and for steady state are analyzed. comparison and operational limits of positive and negative sequence operation are performed, and simulations and experiments are executed to verify the proposed.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1701-1703
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• 2002

This paper introduces a on-line monitoring system for insulation diagnosis of high-voltage motor stator windings. This system monitors the insulation condition of the stator winding with sensor, coupling capacitor. Partial discharge (PD) signals are able to be continuously measured and digitalized with a Peak-hold A/D converter to build the database of the high-voltage motor's insulation condition. This system can communicate with the central monitoring system via RS-485 This paper introduces an economic solution for data acquisition of partial discharges.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1147-1156
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• 2014

This study proposes a quasi-fixed-frequency hysteresis current tracking control strategy for modular multilevel converters (MMCs) on the basis of voltage partition principle. First, by monitoring the grid voltage and the deviation between the output and reference currents, the output voltage is determined, thus prompting the output current to quickly and efficiently track the given current. Second, the voltages of the upper/lower capacitor of the arm and the voltages between the upper and lower arms are balanced by combining these arms with virtual loop mapping and arm voltage balance control, respectively. In particular, the proposed method is designed for any level and number of sub-modules. The validity of the proposed method is verified by simulations and experimental results of a five-level MMC prototype.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.8
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• pp.779-791
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• 1990

This paper presents a knowledge based system to solve reactive power/voltage control problem in a power system. A need is recognized for new methods to alleviate a bus voltage limit violation more quickly when a power system becomes an emergency state due to contingency. To cope with this object, a set of indices concept which is used to make bus order list of reactive power injection priority is introduced. A set of indices, based on the overall system conditions, consists of steady state stability index, reactive power transmittance indes, voltage severity index and generator fuel cost index. This scheme and empirical rules of the knowledge on the basis of the human expert result in fast decision-making of the reactive power compensation devices since only the amount of devices is determined by the inference in the knowledge based system when the voltage violation is detected. In this approach, control devices such as shunt capacitor (reactor), transformer tap settings and generator voltages are utilized. Also the developed system herein can be used to minimize control action taken or generator fuel cost according to the user's option on the weighting factor. The results of a case study are also presented.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.246-253
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• 2013

The Modular Multilevel Converter (MMC) with full bridge cells is available for utility interactive inverter in high voltage line. When it is interconnected with power line, it is possible to control the active power flow in order to supply or charge the power in the line. This research applied the MMC to grid connection system of distributed generator and a power flow control for the MMC is investigated. Theory of power flow between the MMC and the power line is described and control method of power flow and capacitor voltages on arm cells for the MMC are proposed. And effectiveness of the proposed control method is presented by simulation.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.1
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• pp.76-83
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• 2007

This paper describes a low power ROM using single charge-sharing capacitor and hierarchical bit line (SCSC-ROM). The SCSC-ROM reduces the power consumption in bit lines. It lowers the swing voltage of bit lines to a very small voltage by using a charge-sharing technique with a single capacitor. It implements the capacitor with dummy bit lines to improve noise immunity and make easy to design. The hierarchical bit line further saves the power by reducing the capacitance in bit lines. The SCSC-ROM also reduces the power consumption in control unit and predecoder by using the hierarchical word line decoder. The simulation result shows that the SCSC-ROM with $4K{\times}32bits$consumes only 37% power of a conventional ROM. A SCSC-ROM chip is fabricated in a $0.25{\mu}m$ CMOS process. It consumes 8.2mW at 240MHz with 2.5V.