• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.7
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• pp.332-338
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• 2000

In this paper, a robust nonlinear excitation controller is proposed to achieve both voltage regulation and system stability enhancement for single machine-infinite power systems. The proposed method employs backstepping technique and combines this with an adaptation algorithm for estimating the effective reactance of transmission line, thereby leading to adaptive nonlinear control. Simulation results show that power that angle stabilization as well as voltage regulation is achieved in a satisfactory manner, regardless of the system operating conditions and system structure.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.2
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• pp.93-101
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• 2002

This paper describes a new method for determining the permissible operating range of DG(Distributed Generation) when DG is introduced into power distribution systems of which the voltage is controlled by LDC(Line Drop Compensator). Much of the DG installed during the next millennium will be accomplished through the reconstruction of the electric power industry. But in that case, it is difficult to properly maintain the terminal voltage of low voltage customers by using only LDC. This paper presents a method for determining the permissible operating range of DG for proper voltage regulation of power distribution systems with LDC. Proposed method has been applied to a 22.9 kV model and practical distribution systems, and its result is almost identical with the simulation result.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.4
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• pp.255-261
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• 2004

This paper presents an improved droop method which minimizes the voltage droop of a parallel-connected power supply Conventionally, the droop method has been used to achieve a simple structure and no-interconnections among power sources. However, it has a trade-off between output voltage regulation and load sharing accuracy In this paper, the droop is minimized with a current and droop gain control using steady-stage estimation. The proposed method can achieve both good voltage regulation and good load sharing. A design example of two 10㎸, 100㎃ parallel modules is made and tested to verify the proposed current-sharing method.

• Journal of Power Electronics
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• v.9 no.1
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• pp.124-131
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• 2009

This paper presents a PWM dc-ac converter regulation using a Single Input Fuzzy PI Controller (SIFPIC). The SIFPIC is derived from the signed distanced method, which is a simplification of a conventional fuzzy controller. The simplification results in a one-dimensional rule table, that allows its control surface to be approximated by a piecewise linear relationship. The controller multi-loop structure is comprised of an outer voltage and an inner current feedback loop. To verify the performance of the SIFPIC, a low power PWM dc-ac converter prototype is constructed and the proposed control algorithm is implemented. The experimental results show that the SIFPIC performance is comparable to a conventional Fuzzy PI controller, but with a much reduced computation time.

• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.273-280
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• 2012

Most variable speed wind turbines have pitch control mechanisms and one of their objectives is to protect turbines when the wind speed is too high. By adjusting pitch angles of wind turbine, the inlet power and the torque developed by the turbine are regulated. In this paper, the difference between the real wind speed and its rated value is regarded as a disturbance, and a component called disturbance observer (DOB) is added to the pre-designed control loop. The additional DOB based controller estimates the disturbance and generates a compensating signal to suppress the effect of disturbance on the system. As a result, the stability and the performance of the closed loop system guaranteed by an outer-loop controller (designed for a nominal system without taking into account of disturbances) are approximately recovered in the steady state. Simulation results are presented to verify the performance of the proposed control scheme.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.850-852
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• 1993

A buck-boost zero current switched(ZCS) series resonant AC to DC converter for the DC output voltage regulation together with high power factor is proposed. A dynamic model for this AC to DC converter is developed and an analysis for the internal operational characteristics is explored. With the proposed control technique, the unity power factor and the DC output voltage regulation without a current overshoot can be obtained.

• Proceedings of the KIEE Conference
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• summer
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• pp.60-63
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• 2004

AGC is widely used to regulate the frequency of power systems. It is also used to control the frequency of Korean Power System. Control strategies depends on systems to which it is applied. Korean Power System consists of one control area and it has no tie-line. In this research, we have developed a simulation tool to confirm AGC dynamics. The developed tool has been verified by two-machine three-bus system. Moreover an AGC control strategy has been suggested to avoid contradiction with governor dynamics. Low pass filter with relatively long time constant showed good regulation performance. This simple strategy is expected to be applied to New EMS in KPX to get reasonable AGC regulation performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.2
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• pp.106-117
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• 2022

Multiple output converters can be utilized when various output voltages are required in applications. Recently, one of the multiple output converters called fly-buck has been proposed, and has attracted attention due to the advantage that multiple output can be easily obtained with a simple structure. When constant on-time (COT) control is applied, the output ripple voltage must be treated carefully for control stability and voltage regulation characteristics in consideration of the inherent energy transfer characteristics of the fly-buck converter. This study analyzes the operation principle of the fly-buck converter with a ripple generation network and presents the design guideline for the improved output voltage regulation. Validity of the analysis and design guideline is verified using a 5 W prototype of the COT controlled fly-buck converter with a ripple generation network for telecommunication auxiliary power supply.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.35-38
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• 1996

A new high power factor converter using transformer magnetizing energy for power factor correction with a single-switch/single-stage is proposed. The proposed converter gives the good power factor correction, low current harmonic distortions, and tight output voltage regulation. The prototype shows the IEC555-2 requirements are met satisfactorily with nearly unity power factor.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.430-432
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• 2005

This paper presents a novel, single stage, isolated, three-phase switching rectifier capable of switching at high frequency. The circuit topology Provides zero-voltage switching for all switches, output voltage regulation, unity input power factor, all in a single power conversion stage. Operating principle and experimental results in the 48V/100A DC power supply of three-phase single stage method are presented.