The purpose of this paper is to introduce, examine, and evaluate the industrial experiences and effectiveness of a Thyristor Controlled Series Compensator (TCSC) replica controller installed in Korea ...in 2019 through a review of its configuration, test platform, and practical application, and further to propose operational guidelines for replica controllers. Four representative practical cases were conducted: a Dynamic Performance Test (DPT) under a sufficiently large-scale power system prior to the Site Acceptance Test (SAT), pre-verification for on-site controller modification during operation stage, parameter tuning to mitigate the control interaction, and time domain simulation for Sub-Synchronous Torsional Interaction (SSTI). None of these four cases can be performed in a Factory Acceptance Test (FAT) or on-site. Therefore, TCSC control performance was accurately verified under the entire Korean power system based on a large-scale real-time simulator, which demonstrated its effectiveness as a powerful tool for operations including multiple power electronics devices. Our review herein of these four practical cases is expected to show the usefulness of replica controllers, to demonstrate their strength to deal with practical field events, and to contribute to the further expansion of the application area from a perspective of electric utility.
The responses of an inverter-based distributed generator (IBDG) to abnormal voltage and frequency are different from those of a conventional generator because of the inverter's operating modes. In ...particular, although the momentary cessation (MC) mode is essential to protecting the distribution system, the MC mode can affect the power system transient stability by temporarily ceasing significant amounts of IBDG generation. To mitigate these negative effects, this study analyzed the impacts of MC capability on the power system transient stability. First, the transient stability was analyzed in relation to MC capability using the single-machine equivalent (SIME) method. A critical MC operating point (CMCOP) was then proposed to assess the severity of a transient impact and to secure the transient stability under the contingency conditions. A case study based on the Korean power system validated the feasibility and effectiveness of the proposed method.
This study proposes a time-series analysis approach and a non-linear dynamics originated method to detect sub-synchronous oscillation in power systems. Mathematical expressions of the fundamental ...instantaneous signal and sample discrete signal of peak values are derived to examine the phenomenon of interaction between power system components. The results of the circulating trajectory are shown in a two-dimensional map of the calculated root-mean-square value and estimated Floquet multiplier when two signals of different modes are mixed. Without applying a digital filter or frequency decomposition, non-linear oscillation detection is possible by monitoring a non-linear oscillatory index based on the maximum Lyapunov exponent.
Efforts to reduce greenhouse gas emissions constitute a worldwide trend. According to this trend, there are many plans in place for the replacement of conventional electric power plants operating ...using fossil fuels with renewable energy sources (RESs). Owing to current needs to expand the RES penetration in accordance to a new National power system plan, the importance of RESs is increasing. The RES penetration imposes various impacts on the power system, including transient stability. Furthermore, the fact that they are distributed at multiple locations in the power system is also a factor which makes the transient impact analysis of RESs difficult. In this study, the transient impacts attributed to the penetration of RESs are analyzed and compared with the conventional Korean electric power system. To confirm the impact of the penetration of RESs on transient stability, the effect was analyzed based on a single machine equivalent (SIME) configuration. Simulations were conducted in accordance to the Korean power system by considering the anticipated RES penetration in 2030. The impact of RES on transient stability was provided by a change in CCT by increasing of the RES penetration.
This article presents a microstructural study of TiN/carbon steel functionally gradient materials (FGM) processed by of high-energy electron beam irradiation. The mixtures of TiN powders and flux ...were deposited on a plain carbon steel substrate, and were irradiated using an electron beam accelerator. The microstructures of the irradiated surface layer consisted of surface region, melted region, interface, coarse-grained heat-affected zone (HAZ), fine-grained HAZ, and unaltered matrix. Residual pores and TiN powder agglomerates were found in the sample processed without flux, whereas these defects were hardly observed in the samples processed with a considerable amount of flux. As a result of irradiation, the Ti content decreased along the depth from the irradiated surface, thereby yielding the characteristics of FGM. Owing to the dissolved Ti and the formation of fine cuboidal Ti(C,N) particles, the hardness of the irradiated surface layer was greatly improved, reaching as much as twice or three times that of the original matrix, but the hardening effect was reduced along the depth from the surface.
The present study aims at providing the basic data for the establishment of using conditions of work rolls by investigating the microstructure, hardness, and fracture toughness of the five currently ...commercialized work rolls and by clarifying their respective fracture mechanisms. They are high speed steel roll (HSS roll), high chromium cast iron roll (Hi-Cr roll), Ni-grain cast iron roll (Ni-grain roll), Adamite roll, and ductile cast iron roll (DCI roll). The microfracture behavior was observed by using an in situ loading stage installed inside a scanning electron microscope (SEM) chamber, while simultaneously measuring apparent fracture toughness. These experiments enable evaluation and interpretation of fracture toughness, and thus the results are expected to be used as the basic data for the selection of work rolls depending on the rolling stands.
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