• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.4
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• pp.168-176
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• 2000

This paper presents the Hessenberg method, a new sparsity-based small signal stability analysis program for large interconnected power systems. The Hessenberg method as well as the Arnoldi method computes the partial eigen-solution of large systems. However, the Hessenberg method with pivoting is numerically very stable comparable to the Householder method and thus re-orthogonalization of the krylov vectors is not required. The fractional transformation with a complex shift is used to compute the modes around the shift point. If only the dominant electromechanical oscillation modes are of concern, the modes can be computed fast with the shift point determined by Fourier transforming the time simulation results for transient stability analysis, if available. The program has been successfully tested on the New England 10-machine 39-bus system and Korea Electric Power Co. (KEPCO) system in the year of 2000, which is comprised of 791-bus, 1575-branch, and 215-machines. The method is so efficient that CPU time for computing five eigenvalues of the KEPCO system is 3.4 sec by a PC with 400 MHz Pentium IIprocessor.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.93-95
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• 2002

This paper presents the design of a Unified Power Flow Controller(UPFC) for enhancing the small signal voltage stability in the multi-machine power systems. Recently a lot of attention has been paid to the subject of dynamic stability. The paper deals with analysis of eigenvalue sensitivities with respect to parameters of UPFC Controller. The series branch of the UPFC is designed to damp the power oscillation during transients, while the shunt branch aims at maintaining the bus voltage. Comprehensive time-domain simulation studies using Pss/E show that the proposed robost UPFC controller can enhance the small signal stability efficiently in spite of the variations of power system operating conditions.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1299-1301
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• 1999

This paper describes a initial screening methods for weak line selection using sensitivity matrix. The elements of sensitivity matrix for line suceptance have 1 or -1, 0. From this property of sensitivity matrix, the eigen-sensitivity for line suceptance can be computed very simply and selected weak line for small signal stability or transient stability. The proposed algorithm is applied to small signal stability of New England 39-bus system and also applied to voltage stability of New England 30-bus system too.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.387-389
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• 2006

This paper describes new on-line small signal stability assessment and its application using the time series simulated phasor measurement data. Using FFT technique and optimization method, the suggested method can effectively identify all of mode frequencies involved in measured data and calculate the damping ratio with accuracy.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2003.06a
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• pp.188-192
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• 2003

Pole placement method is widely used in controller design. For the stability of the closed loop system, user-specified desired locations including extra pole locations in the s-plane is chosen and by some procedure, feedback gain is obtained. In this paper, only desired pole location is used, and the calculation process is done for attaining linear quadratic stability. Similarly transformation is used for this. By computer simulations using MATLAB, the effectiveness is shown.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.5
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• pp.131-138
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• 1996

This paper suggests a servo control algorithm to reduce the repeatable tracking error which is not explicitly taken into account in the design of a conventional PID controller of a computer hard disk drive. The robust stability of the repetitive control system with multiplicative modelling error is analyzed, and the controller was implemented using a fixed point DSP(Digital Signal Processor). Experimental results show that the repetitive errors are suppressed effectively by the proposed controller.

• Journal of electromagnetic engineering and science
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• v.9 no.3
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• pp.118-123
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• 2009

This paper discusses the design and fabrication of a reference signal generator for a naval radar system, including the vibration environment test. The transmit signals of the S-band radar system are synthesized by the reference signal and the phase noise must lower than - 130 dBc/Hz at a 10 kHz offset frequency. To achieve this specification, the phase noise of the reference signal needs to be less than -165 dBc/Hz at a 10 kHz offset. For achieving very low phase noise performance by the reference signal generator, the phase locked loop technique is applied with a 10 Hz loop bandwidth. Also, this reference signal generator has ${\pm}0.35\;ppb$ short-term stability to minimize instant phase errors and high vibration sensitivity against a ship's shaking, unbalanced rotating of antennas and so on.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.2
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• pp.231-236
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• 2016

The stability of DGPS signal in the DGPS service area was measured and the service availability according to the receiving signal strength was analyzed in this paper. Based on the effects of radio wave propagation in the seasons of winter and summer, daytime and night, the method to provide the DGPS service coverage was presented in this paper. The signal's strength of DGPS radio wave were measured at a constant distance from the DGPS reference station during a constant period. The propagation of DGPS radio wave is affected by status of ground conductivity, so the DGPS service area is dependant on the ground conductivity. To provide the stable service coverage, it is necessary to apply the adaptive power control for receiving signal's variations and the antenna design for alleviation of high elevation's radiation.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.306-315
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• 2017

This study introduces a software for real-time assessment of combustion stability for utility gas turbines. The software was written with LabView, and implemented the time-domain kurtosis as a parameter to proactively access the instantaneous combustion stability during operation of the industrial gas turbine. The simple time-domain assessment algorithm incorporated in the software is advantageous over conventional frequency-domain signal processing of dynamic pressure signal since it reduces the computational cost, thereby making the algorithm more appropriate for real-time monitoring of combustion stability. Benchmark data obtained from a model gas turbine combustor were used for the reproducibility test of the software. The assessment obtained from the software agreed well with previously published results, indicating that incorporation of the software could enhance the performance of systems monitoring the combustion stability for gas turbines during power generation.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.155-158
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• 1997

In this paper, we present new results concerning the relationship between the input-output and Lyapunov stability of nonlinear system possessing a periodic orbit. Definition of small-signal finite-gain L$\sub$p/ stability around periodic orbit is introduced. We show L$\sub$p/ stability of exponentially stable periodic orbit using quadratic Lyapunov functions for the periodic orbit. The L$\sub$2/ gain analysis is presented with Hamiltonian-Jacobi inequality along with an example.