• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권8호
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• pp.522-528
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• 2000

In this paper, a static synchronous compensator(STATCOM), which in general compensates reactive power, is proposed in order to balance the unbalanced loads. Reference values for the compensation of the unbalanced loads currents are determined by 3-phase circuit analysis result. Also the STATCOM control unit is designed considering the proposed compensation scheme for the unbalanced loads. As a result, the effectiveness of the STATCOM for balancing the load currents is verified by computer simulations.

• 한국정보통신학회논문지
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• 제17권11호
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• pp.2563-2568
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• 2013

최근 옥외용 이동통신시스템과 동일 주파수를 사용하면서 추가적으로 용량을 확보할 수 있는 옥내용 모바일 통신 시스템을 위한 초소형 기지국에 대한 연구 및 개발이 활발히 진행되고 있다. 본 연구에서는 옥내용 모바일 통신 시스템에서 초소형 기지국의 특성을 고려한 시스템 레벨 시뮬레이터를 개발하였고 초소형 기지국 환경에서 혼잡한(Congested) 기지국의 아웃티지 확률(Outage Probability)을 줄이는 적응적 Load-Balancing 방안을 제안하였다. 본 시뮬레이터에서는 초소형 기지국 특성을 고려한 링크 레벨 시뮬레이션 결과를 반영하였으며, 본 시뮬레이터를 이용하여 옥내용 모바일 통신 시스템에서 Load-Balancing 방안을 적용하였을 때와 적용하지 않았을 때의 아웃티지 확률을 비교해 보았다. 제안한 Load-Balancing 방안의 사용을 통해 혼잡한 기지국의 아웃티지 확률을 줄이고 전체 시스템의 성능을 향상시킬 수 있음을 보였다.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.71-79
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• 2014

This paper discusses a method for the determination of frequency control reserve requirement with consideration of the interaction between ex-ante planning and real-time balancing. In proposed method, we consider the fact that the delivered energy for tertiary control reserve is determined based on required capacity for secondary control reserve and the expected amount of load errors. Uncertain load errors are derived by Brownian motion, an optimization method is suggested using a stochastic programming. In a short, we propose an interactive dependent method for determining secondary control reserve requirement based on the principle that it satisfies to minimize the total cost. As a result, this paper provides will analyze for an example model to demonstrate the capabilities of the method.

• 동력기계공학회지
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• 제11권1호
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• pp.134-139
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• 2007

A delivery ship is used to handle the cargo with the crane to/from the ships. The ship is inclined in the direction of a cargo which is hung on a crane. In this case, a arc shaped rail should be in the equilibrium state to get good anti-rolling performance. In this study, a device and control algorithm are developed to take accurate and quick equilibrium of the rail. The device is composed of a hinged immovable support, screw jack and damper. And the control system is based on I-PD control law to consider of control input saturation and overshoot. The controller is composed of integral controller of feedforward path and proportional-derivative controller of feedback path. The parameters of controller is designed to follow the reference signal and to remove overshoot. The simulation results show that the desirable control performance is achieved.

• 대한기계학회논문집A
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• 제27권5호
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• pp.688-696
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• 2003

The casing oscillator used for basic construction of buildings, factories and bridges is a construction machine, which rotates and rolls the casing to insert it into the ground. It is very important that the casing is positioned perpendicular to the sea level regardless of the slope of the ground. In this paper, we present a new casing oscillator that doesn't need additional work to level the ground for the casing insertion. The kinematic analysis fur work space of a casing oscillator is presented and carried out with auto-balancing of the casing oscillator using posture feedback control.

• 한국시스템다이내믹스연구
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• 제12권1호
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• pp.75-87
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• 2011

Congestion problems can be approached from the viewpoint of system dynamics theory. The relationship between road capacity and congestion can be explained by the 'relative control' archetype among four system archetypes suggested by Wolstenholme. There is a balancing feedback loop between road capacity and road congestion. However, there is another balancing loop between road congestion and car traffic volume, which keeps disrupting the equilibrium of the former loop. A system dynamics model, which is based on a partial adjustment model of induced traffic in the literature, is built to simulate three road building scenarios: 'Expanding investment', 'Balancing investment' and 'Frozen road investment' scenarios. The 'Expanding investment' scenario manages to drop congestion levels by 9% over 30 years, however, causing much higher emissions of $CO_2$ than other scenarios. The trade-off relationship between congestion levels and environmental costs must be taken into consideration for road investment policies.

• 제어로봇시스템학회논문지
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• 제22권10호
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• pp.826-832
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• 2016

A two-wheeled balancing mobile robot (TWBMR) has the characteristics of both nonlinear and underactuated system. In this paper, the disturbances acting on a TWBMR are classified into body disturbance and wheel disturbance. Additionally, we describe a nonlinear disturbance observer, which is suitable as a single input multi-output (SIMO) system for the longitudinal motion of TWBMR. Finally, we propose a reasonable disturbance compensation technique that combines the indirect reference input of equilibrium point and the direct torque compensation input. Simulations and experimental results show that the proposed disturbance compensation method is an effective way to achieve robust postural stability, specifically on inclined terrains.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2137-2142
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• 2003

One of the important performance metrics of the World Wide Web is how fast and precise a request from users will be serviced successfully. Shared Web Caching (SWC) is one of the techniques to improve the performance of the network system. In Shared Web Caching Systems, the key issue is on deciding when and where an item is cached, and also how to transfer the correct and reliable information to the users quickly. Such SWC distributes the items to the proxies which have sufficient capacity such as the processing time and the cache sizes. In this study, the Hot Spot Prediction Algorithm (HSPA) has been suggested to improve the consistent hashing algorithm in the point of the load balancing, hit rate with a shorter response time. This method predicts the popular hot spots using a prediction model. The hot spots have been patched to the proper proxies according to the load-balancing algorithm. Also a simulator is developed to utilize the suggested algorithm using PERL language. The computer simulation result proves the performance of the suggested algorithm. The suggested algorithm is tested using the consistent hashing in the point of the load balancing and the hit rate.

• 전기학회논문지
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• 제59권4호
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• pp.707-714
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• 2010

When problems such as line fault, breakdown of a substation or a generator, etc. arise on the grid, the Microgrid is designed to be separated or isolated from the grid. Most existing DGs(Distributed Generators) in distribution system use rotating machine. However, new DGs such as micro gas turbine, fuel cell, photo voltaic, wind turbine, etc. will be interfaced with the Microgrid through an inverter. So the Microgrid may have very lower inertia than the conventional distribution system. By the way, the rate of change of frequency depends on the inertia of the power system. Moreover, frequency has a strong coupling with active power in power system. Because the frequency of the Microgrid may change rapidly and largely during transient, appropriate and fast control strategy is needed for stable operation of the Microgrid. Therefore, this paper presents a power balancing strategy in Microgrid during transient. Despite of strong power or frequency excursions, power balancing in the Microgrid can be maintained.

• 전자공학회논문지
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• 제51권10호
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• pp.45-49
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• 2014

이기종 셀룰러 네트워크에서는 셀 계층간 접속되는 사용자의 수가 크게 달라지고, 이로 인해 사용자와 기지국 연결을 최적화하는 로드 밸런싱(load balancing)이 필수적으로 요구되어진다. 그러나 로드 밸런싱을 위하여 셀의 크기를 조정하는 경우 간섭량이 증가하는 문제점이 발생한다. 본 논문에서는 이기종 셀룰러 시스템(heterogeneous cellular system)에서 다중 수신 안테나를 이용하여 인접 셀로부터 오는 간섭을 제거할 때, 사용자와 기지국 사이의 연결을 최적화하고 사용자들의 전송 용량 성능을 확인한다. 결과적으로 다중 안테나 간섭 제거 기법을 적용하면, 로드 밸런싱이 이루어진 이기종 셀룰러 시스템의 성능을 크게 향상시킬 수 있음을 모의실험 결과를 통해 보여준다.