• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.1971-1979
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• 2010

As a result of increasing environmental concern, the penetration of renewable power on power systems is now increasing. Wind energy can be considered as the most economical energy sources to generate electricity without depletion of fossil fuel. To devise adequate control strategies for wind farm, time domain simulation analysis needs to be performed. This presents a continuation time integration (CTI)-based time domain simulation algorithm for wind farm with doubly fed asynchronous generator (DFAG) connected to the external power systems. This paper depicts how to time trajectories are traced using CTI-based time domain simulation. Also this paper describes the possibilities of hierachical control for wind farm output limitation, and the coordinated control has been designed by hierarchical control structured from central control level to wind farm control board and to an individual wind turbine level. Finally it shows an illustrative example of time domain simulation result with two test systems through case study.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.5
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• pp.457-463
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• 2006

Recently proposed control scheme for a stable teleoperation, which was based on two-port time-domain passivity approach[21], has been successful for a contact with high stiffness environments. However, we found several conservatisms during the contact with deformable environments and unconstrained motion. The two-port time-domain passivity controller was excessively dissipating energy even though it was not necessary for some cases of an unconstrained motion and soft contact. The main reason of those conservatisms was on the fact that the two-port time-domain passivity controller was activated without considering the amount of energy dissipation at the master and slave manipulators. Especially, the exclusion of the slave manipulator from the two-port was the dominant reason of the conservatisms. In this paper, we consider the amount of energy dissipation at slave manipulator for designing the time-domain passivity observer and controller. The measured interaction force between slave manipulator and environment allow the time-domain passivity observer to include the amount of energy dissipation at the slave manipulator. Based on the modified passivity observer, reference energy following method[24] is applied to satisfy the passivity condition in real-time. The feasibility of the developed methods is proved with experiments. Improved performance is obtained for an interaction with deformable environments and an unconstrained motion.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.107-112
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• 2005

Recently proposed stable teleoperation control scheme, base on time domain passivity, is modified to remove several conservatisms. During unconstrained motion and contacting with soft and deformable environments, the two-port time domain passivity approach [21] was excessively dissipating energy even though it was stable without any energy dissipation. The main reason of this conservatism is on the fact that the time domain passivity controller does not include the external energy dissipation elements at the slave manipulator. The measured interaction force between slave and environment allow the time domain passivity observer to include the amount of energy dissipation of the slave manipulator to the monitored energy. With the modified passivity observer, reference energy following idea [24] is applied to satisfy the passivity condition. The feasibility of the developed methods is proved with experiments. Improved performance is obtained in unconstrained motion and contacting with a soft environment.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.10a
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• pp.6-10
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• 1996

This paper presents an overview of research results obtained by the authors in a series of publications. Methods are developed both for time-varying and time-invariant for linear and nonlinear. for time domain and frequency domain . and for discrete-time and continuous-time systems. Among the topics presented are: 1. Learning control based on integral control concepts applied in the repetition domain. 2. New algorithms that give improved transient response of the indirect adaptive control ideas. 4. Direct model reference learning control. 5 . Learning control based frequency domain. 6. Use of neural networks in learning control. 7. Decentralized learning controllers. These learning algorithms apply to robot control. The decentralized learning control laws are important in such applications becaused of the usual robot decentralized controller structured.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.58-66
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• 2001

GPC has been reported as a useful self-tuning control algorithm for systems with unknown time-delay and parameters. GPC is easy to understand and implement, and thus has won popularity among many practicing engineers. Despite its success, GPC does not guarantee is nominal stability. So, in this paper, GPC is rederived in frequency domain instead of in the time domain to guarantee its nominal stability. Derivation of GPC in frequency domain involves spectral factorization and Diophantine equation. Frequency domain GPC control law is stable because the zeros of characteristic polynomial are strictly Schur. Recursive least square algorithm is used to identify unknown parameters. To see the effectiveness of the proposed controller, the controller is simulated for a numerical problem that changes in dead-time, in order and in parameters.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.3
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• pp.270-276
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• 2014

This survey paper reviews robust control problems in both frequency domain and time domain. Robust control is focused on model uncertainties such as modeling error, system parameter variations, and disturbances. Robust control design problems are discussed according to parameter uncertainty, polytopic uncertainty, and norm-bounded uncertainty. Nowadays, robust control theory is combined with various control theory such as model predictive control, adaptive control, intelligent control, and time delay control.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.207-214
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• 2019

In this study, discrete-time domain analysis is proposed to investigate the input current of a buck AC/DC light-emitting diode (LED) driver. The buck power factor correction converter can operate in both discontinuous conduction mode (DCM) and continuous conduction mode (CCM). Two discontinuous and two continuous conduction operating modes are possible depending on which event terminates the conduction of the main switch in a switching cycle. All four operating modes are considered in the discrete-time domain analysis. The peak current-mode control with slope compensation is used to design a low-cost AC/DC LED driver. A slope compensation design of the buck AC/DC LED driver is described on the basis of a discrete-time domain analysis. Experimental results are presented to confirm the usefulness of the proposed analysis.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.984-990
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• 1994

In this paper a new speech synthesis method in the time domain using mono-syllables is proposed. It is to overcome the degradation of the synthetic speech quality by the synthesis method in the frequency domain and to develop an algorithm in the time domain for the prosodic control. In particular when we use a method in a time domain with mono-syllable as a synthesis unit it will be the main issues which are to control th pitch period and to smooth the energy pattern. As a solution to the pitch control, a method using Lagrange interpolation is suggested. As a solution to the other problem, an algorithm which can control the amplitude envelop shape of mono-syllable is proposed. As the results of experiments it was possible to synthesize unlimited Korean speeches including the prosody control. Accoding to the MOS evaluation the quality and the naturality in them was improved to be a good level.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.11
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• pp.1124-1129
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• 2008

Recently, two-port time-domain passivity approach was modified for time-varying communication delay. The newly proposed approach could achieve stable teleoperation even under the serious time-varying delay and packet loss communication condition. However, after some operation hour, the accumulated energy difference between the input energy from one port and the output energy at the other port caused unstable behavior until the passivity controller is activated. Resetting scheme is introduced for solving this problem, and stable bilateral teleoperation can be guaranteed without worrying about the accumulated energy difference.

• Journal of Power Electronics
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• v.7 no.3
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• pp.213-221
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• 2007

A digital state feedback control method for the current mode control of DC-DC converters is proposed in this paper. This approach can precisely achieve interleaved current sharing among the converter modules. As the controller design and system analysis are performed in the time domain, the proposed method can easily satisfy the required converter specification by using the pole placement technique. The digital state feedback controller in the continuous and discrete time domain is derived for the robust tracking control. For the verification of the proposed control scheme, a parallel module bi-directional converter in a prototype 42V/14V hybrid automotive power system, which is a design example in the continuous time domain, and a parallel module buck converter, which is a design example in the discrete time domain, are implemented using a TMS320F2812 digital signal processor (DSP).