• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 C
• /
• pp.1331-1333
• /
• 1999

In Haenam-Cheju HVDC link several modes of operations and controls are provided, which are constant frequency control, constant power control and constant current control. This paper describes basic control action of converters under three control modes and shows EMTDC simulation results at ground fault and steady state respectively.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2008년도 제39회 하계학술대회
• /
• pp.211-212
• /
• 2008

As a result of environmental concerns, the production of electricity through renewable energy resources is rapidly increasing. Wind energy is among the fastest growing renewable energy resources now being integrated in the power system, and the penetration rate of wind generation has been gradually increased. For power flow analysis of the recent systems, thus, steady-state modeling of wind turbines and their application are of great importance. This paper presents the procedure we applied for implementation of a steady-state wind turbine model in power flow.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2016년도 추계학술대회 논문집
• /
• pp.63-64
• /
• 2016

This paper deal with single module design of 13.2kVrms/10kVA solid state transformers exchanging conventional transformer. We can design compact hardware system to reduce size and get higher switching frequency by using SiC devices. As a result by comparing simulation results with experiment result, it is verified.

• 대한전기학회논문지
• /
• 제34권5호
• /
• pp.201-209
• /
• 1985

This paper describes a method for the state estimation by a modified fast decoupled estimation method and system decomposition. The state values are gained by using the weighted least square estimation method, fast decoupled estimation method, and modified fast decoupled estimation method. The estimated values of each method were compared about effectiveness of state values, respectively. This paper investigated the effects of impedance of well-condition or ill-condition into lines. The characteristics of state estimation were gained through hierarchical state estimation. Each method was applied to three model power systems, and, the results of test for the proposed method are given.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제14권7호
• /
• pp.3134-3155
• /
• 2020

In this paper, we study the joint radio and computational resource allocation in the ultra-dense mobile-edge computing networks. In which, the scenario which including both computation offloading and communication service is discussed. That is, some mobile users ask for computation offloading, while the others ask for communication with the minimum communication rate requirements. We formulate the problem as a joint channel assignment, power control and computational resource allocation to minimize the offloading cost of computing offloading, with the precondition that the transmission rate of communication nodes are satisfied. Since the formulated problem is a mixed-integer nonlinear programming (MINLP), which is NP-hard. By leveraging the particular mathematical structure of the problem, i.e., the computational resource allocation variable is independent with other variables in the objective function and constraints, and then the original problem is decomposed into a computational resource allocation subproblem and a joint channel assignment and power allocation subproblem. Since the former is a convex programming, the KKT (Karush-Kuhn-Tucker) conditions can be used to find the closed optimal solution. For the latter, which is still NP-hard, is further decomposed into two subproblems, i.e., the power allocation and the channel assignment, to optimize alternatively. Finally, two heuristic algorithms are proposed, i.e., the Co-channel Equal Power allocation algorithm (CEP) and the Enhanced CEP (ECEP) algorithm to obtain the suboptimal solutions. Numerical results are presented at last to verify the performance of the proposed algorithms.

• 한국전자파학회논문지
• /
• 제27권1호
• /
• pp.92-95
• /
• 2016

본 논문에서는 UHF 대역인 900 MHz에서 열음향 영상(thermoacoustic imaging, TAI) 응용을 위한 1 kW급 반도체 펄스 전력 증폭기를 설계 및 제작하였다. 반도체 펄스 전력 증폭기는 단펄스(short pulse) 동작을 위하여 펄스 폭 $80{\mu}s$, 듀티사이클 1 %, 900 MHz의 캐리어 주파수 조건에서 설계되었다. 전체 전력 증폭기는 16개의 단일 전력 증폭기를 윌킨슨 전력 분배기를 통해 결합하여 제작되었고, 사용된 능동 소자는 Freescale사의 MRFE6P9220HR3 LDMOSFET이 사용되었다. 제작된 전력 증폭기는 입력 전력이 -16 dBm일 때 중심주파수에서 60.2 dBm의 출력 전력과 76.2 dB의 전력 이득, 그리고 25 %의 드레인 효율 특성을 나타내었다.

• Journal of Electrical Engineering and Technology
• /
• 제9권4호
• /
• pp.1385-1393
• /
• 2014

Gas insulated switchgear (GIS) is widely used in the power systems, however, the contacts overheating of the inside circuit breaker or disconnector may be a potential cause of developing accidents. As the temperature of the contacts cannot be directly acquired due to existence of the metallic shield, an infrared sensor is adopted to directly measure the temperature of the shield and then the contacts temperature can be indirectly obtained by data fitting, based on which the on-line temperature monitoring technology specifically for GIS contacts based on infrared sensing is proposed in this paper. A real GIS test platform is constructed and experimental studies are carried out to account for the influential factors that affect the accuracy of the infrared temperature measurement. A heat transfer model of the GIS module is also developed, together with experimental studies, the nonlinear temperature relationship among the contacts, the metallic shield and the environment based on a neural network algorithm is established. Finally, an integrated on-line temperature monitoring system for the GIS contacts is developed for on-site applications.

• 한국IT서비스학회지
• /
• 제18권3호
• /
• pp.53-74
• /
• 2019

In this paper, a theoretical measurement model for comparing cultural power of nations as a form of national power is built and applied to the G20 nations. The measurement model is drawn from the literature of the state theories regarding culture, theories of epistemology, and debates about the sources of national power. Taking the multiple indicator approach, indicators reflecting diverse aspects of cultural power are developed are developed. Examined with empirical data, this model is proved as appropriate as a tool for measuring and comparing the cultural power of nations. Diverse aspects of the cultural power of the G20 nations are ranked and interesting points regarding the state and potential of Korean culture and her cultural governance in these respects are elaborated. The overall ranking of the cultural power of Korea is found as the $11^{th}$ while the U.S., U.K. and France respectively as the $1^{st}$, the $2^{nd}$, and the $3^{rd}$. The U.S. is ranked as the 1st in all three aspects of the cultural power of nation: cultural attractiveness, efforts to enhance the national cultural power, and cultural base of a nation. Korea is ranked as $14^{th}$, $11^{th}$, and $6^{th}$ respectively in these three respects of the national cultural power. Based upon typological analysis of the cultural power of Korea, it is found that Korea belongs to Type III. Trying to move eventually toward Type I state via Type II is suggested as a strategy movement for future cultural governance by Korean government and people to enhance her national cultural power.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
• /
• pp.534-537
• /
• 1997

Solar power systems have become popular in the modem electric energy system. In order to supply the DC power, generated by solar cells, to the electric power system, the solar power system requires DC-to-AC power conversion. A line-commutated inverter or a forced-commutated inverter can be used in the DC-to-AC power conversion. Because of the nonlinear V-I characteristics of the solar cells, multiple operating points determined by the control mode of the inverter exist in the DC V-I state plane of the solar power system. In this paper, the stability of utility-interactive solar power system with a line-commutated inverter is analyzed at various operating points, using the eigenvalue method and the state-plane analysis technique. The stability of a forced-commutated inverter case is also anaiyzed and compared to that of the line-commutated inverter case.

• 전력전자학회논문지
• /
• 제25권4호
• /
• pp.303-310
• /
• 2020

Estimating the accurate internal state of lithium ion batteries to increase their safety and efficiency is crucial. Various algorithms are used to estimate the internal state of a lithium ion battery, such as the extended Kalman filter and sliding mode observer. A state-space model is essential in using algorithms to estimate the internal state of a battery. Two principal methods are used to express the state-space model, namely, continuous time and discrete time. In this work, the extended Kalman filter is employed to estimate the internal state of a battery. Moreover, this work presents and analyzes the estimation performance of algorithms consisting of a continuous time state-space model and a discrete time state-space model through static and dynamic profiles.