• Korean Journal of Remote Sensing
• /
• v.20 no.4
• /
• pp.227-234
• /
• 2004

The synchronization of Time Delay and Integration (TDI) against the temporal variation of osculating altitude in the operation of high resolution satellite imager was studied. The characteristics of osculating altitude variation was analyzed and its impact on the performance of TDI imger was also investigated. A practical ]me rate control method was proposed to compensate instantaneous TDI mismatch due to the osculating altitude variation, so that geometrical performance enhancement was achieved by the proposed method. This study is applicable to real satellite operation and can be useful for satellite image quality enhancement.

• Journal of the Korean Solar Energy Society
• /
• v.35 no.3
• /
• pp.57-63
• /
• 2015

This paper presents a solution by introducing energy storage system(ESS) to solve an annual blackout due to a typhoon or electrical failure in Udo Island. This island is now receiving electrical power through undersea cables from the Jeju Island. During blackout period, ESS will supply the electricity. And it is necessary to estimate the ESS capacity and control the transient state for the operation of stable power system. For the verification of proposed method, ESS capacities have been estimated according to base load and the minimum capacity of only home appliance in Udo Island. Also, in case of restoring from the fault, the algorithm for synchronization is proposed. Finally, the simulation results by using the PSCAD/EMTDC program will show the feasibility.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.14 no.6
• /
• pp.15-24
• /
• 2004

Electronic commerce is widely used with the development of information communication technologies in internet using public key certificates. And the study for access control in Web application and DB system is also progressed actively. There are many verification method for PKC(Public Key Certificates), which are CRL, OCSP, SCVP and others. But their certificates verification methods for PKC cannot to be applied to PMI(Privilege Management Infrastructure) which is using AC(Attribute certificates) because of synchronization of PKC and AC. It is because AC has no public key, AC Verifier must get the PKC and verify the validity on PKC and AC. So in this paper we proposed the new AC-based certificate verification model. which provide the synchronization in two certificates(AC and PKC).

• Proceedings of the KIEE Conference
• /
• 1991.07a
• /
• pp.877-880
• /
• 1991

In this paper, the architecture of a dataflow logic solving processor for programmable logic controller is proposed. As the proposed DFLSP(dataflow logic solving processor) is designed based on the dataflow architecture, it has inherently concurrent processing and data synchronization capabilities. And also, it has dynamic load balancing capabilites which increases the utilization of the whole system that can he hardly implemented in other multiprocessor system. The re-matching unit gets rid of unnecessary matching cycles in LSU, which increases the performance of LSU and allows the multiple input multiple output operations.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.54 no.8
• /
• pp.486-494
• /
• 2005

This paper presents a design experience of a supervisory control system. For effective programming of job commands, a petri net-type graphical language (PGL) is proposed applied to various tasks having concurrency and synchronization. Our PGL based supervisory control system is composed of PGL editor and PGL compiler; PGL editor is designed to help us to generate a job program using graphical symbols. PGL compiler includes analyzer, scheduler, and tranlator, PGL analyzer prevents a deadlock or resource allocation of unit cell, PGL scheduler generates a adequate job sequence of unit cell. and PGL translator translate the scheduled sequence into the iob program of each unit cell.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.6
• /
• pp.584-591
• /
• 2004

The conventional analog-based firing circuit can be implemented by comparing a linearly decreasing periodic sawtooth waveform synchronized to the ac supply, with a control signal corresponding to the desired converter delay angle. This circuit requires a large number of passive components (resistance and capacitor) and careful adjustment of the synchronization circuity. In this paper a novel firing circuit is proposed for thyristor switch. The proposed circuit is implemented by using digital components(FPGA, A/D, and DSP etc.) on the basis of the analog cosine method.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.9
• /
• pp.562-568
• /
• 2004

The frequency and phase angle of the utility voltage are important in many industrial systems. In the three-phase system, they can be easily known by using the utility voltage vector. However, in the case of single phase system, there are some difficulties in detecting the information of utility voltage. In conventional system, the zero-crossing detection method is widely used, but could not obtain the information of utility voltage instantaneously. In this paper, the new digital PLL control using virtual two phase detector is proposed with a detailed analysis of single-phase digital PLL control for utility connected systems. The experimental results under various utility conditions are presented and demonstrate an excellent phase tracking capability in the single-phase grid-connected operation.

• 제어로봇시스템학회:학술대회논문집
• /
• 1994.10a
• /
• pp.177-182
• /
• 1994

In this paper, an output feedback adaptive variable structure control scheme is presented for stabilization of large scale power systems. An additional input signal which is called a power system stabilizer(PSS) is needed to improve the stability of a power system and to maintain the synchronization of generators. The proposed PSS scheme does not require a priori knowledge of uncertainty bounds. It is guaranteed that the closed-loop system is globally uniformly ultimately bounded by the Lyapunov stability theory. Simulation results for a multimachine power system are given to show the feasibility of the proposed scheme and the superiority of the proposed PSS in comparison with the conventional lead-lag PSS of PID-type.

• Journal of Institute of Control, Robotics and Systems
• /
• v.6 no.11
• /
• pp.943-954
• /
• 2000

Fieldbus is the lowest level industrial network in the communication hierarchy of factory automation and distributed process control systems. Data generated from field devices are largely divided into three categories : time-critical, periodic and time-available data. Because these data share one fieldbus medium, it needs a method that allocates these data to the bandwidth-limited fieldbus medium. This paper introduces an implementation method of bandwidth allocation scheme on PROFIBUS. In order to implement bandwidth allocation scheme on PROFIBUS, the following functions need to be supplemented on the FDL(Fieldbus Datalink Layer) protocol: (i) separation of medium bandwidth into periodic and non-periodic intervals, (ii) synchronization of node timers over a local link. In order to examine the validity of bandwidth allocation scheme on PROFIBUS, this paper develops an experimental model of a network system. The results obtained from the experimental model show that the bandwidth allocation scheme satisfies the performance requirement of time-critical, periodic and time-available data.

• Proceedings of the KIEE Conference
• /
• 1999.07b
• /
• pp.615-617
• /
• 1999

Nowadays the trend has been changed from MHC through EHC to D-EHC in turbine control system. But many plants aren't being operated by D-EHC System. We are trying to retrofit one of the EHC to D-EHC system. In this paper, we are going to introduce an overview of the control logics from turbine prewarming to synchronization of small and medium size power plants, respectively.