• 대한전기학회논문지:시스템및제어부문D
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• 제55권6호
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• pp.279-285
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• 2006

Power line communication channels are very complicated and models for communication channels vary with the types of electrical equipment, devices and load fluctuations. So, modeling and analysis of power line channels for implementation of power line communication systems is a very important process. Power line channel modeling and simulation are performed based on power system transient simulation models and power system CAD tools to create precise and accurate models. In this paper, a channel modeling and simulation method is proposed for power line communication systems using PSCAD/EMTDC, in which a PN 63 sequence code generator is applied for impulse response of the power line channel in the simulation model.

• 수산해양기술연구
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• 제36권1호
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• pp.12-24
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• 2000

The electro-hydraulic servo winch system built in a automatic tension control equipment was designed with a latent need for an advanced system in fishing operations of the inshore and coastal fishing vessels. In order to keep the constant tension condition of warp under loading, a tension control circuit was added to the servo winch system.The dynamic performance in the open loop behaviour of the designed winch system was investigated and its applicability was tested for various possibilities of load using a load generator especially developed in order to this study.The mechanical characteristics of this system is different from that of a conventional type, that is, the tension, length, line speed and drum revolution can be automatically controlled by the information from various sensors, such as torque, rpm and pressure transducers. from the experiment results, it was verified that the servo winch system has very good output and tracking behaviour for the control input signals in different operating conditions though overshoot of out 8% in the transient characteristics of torque under the load though a overshoot of about 8% in the transient characteristics of torque under the load condition can be observed when the opening of servo valve, adjustable by the input voltage between - 10 V up to 10 V, changed suddenly.Consequently, the improved fishing winch system can be effectively used as the automatic shooting and hauling equipment of low cost for small inshore and coastal fishing vessels which engage in net fishing.

• 전기학회논문지
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• 제60권5호
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• pp.999-1004
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• 2011

Nowadays, it is becoming difficult to secure a transmission line route when a new transmission line is constructed due to social environment and resident complaints. As existing urban areas are expanded and new cities are constructed, the necessity of high-capacity underground power transmission has been increasing because of load concentration in downtown areas. In North America, Europe and Japan, the research has been carried out for 2nd generation gas insulated transmission lines(GIL) which is more environmentally friendly and economical compared to previous GILs. The new GILs have been applied to real power systems from early 2000s. In South Korea, GIL is being considered as a possible solution for replacing 345kV high-capacity overhead transmission lines with underground transmission ones, so KEPCO is planning to develop and apply a new 362kV rated GIL underground transmission lines instead of overhead transmission lines. In this paper, the overvoltage generated at the combined transmission line adapting GIL was reviewed using EMTP.

• 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.

• 대한전기학회논문지:전력기술부문A
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• 제54권6호
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• pp.306-314
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• 2005

In this paper, a new approach that is based on EEAC & only with network solutions for CS&S in the transient stability assessment is developed. The proposed CS&S algorithm in conjunction with EEAC to include the capability of performing on-line TSA without TDS is used to calculate the critical clearing time for stability index. In this algorithm, all generators are represented by classical models and all loads are represented by constant impedance load models. The accelerating & synchronizing power coefficient as an index is determined at its disturbance through solving network equation directly. As mentioned above, a new index for generator is generally used to determine the critical generators group. The generator rotor angle is fixed for non-critical generators group, but has equal angle increments for critical generators group. Finally, the critical clearing time is calculated from the power-angle relationship of equivalent OMIB system. The proposed CS&S algorithm currently being implemented is applied to the KEPCO system. The CS&S result was remarkably similar to TSAT program and SIME. Therefore, it was found to be suitable for a fast & highly efficient CS&S algorithm in TSA. The time of CS&S for the 139 contingencies using proposed CS&S algorithm takes less than 3 seconds on Pentium 4, 3GHz Desktop.

• Journal of Power Electronics
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• 제15권2호
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• pp.346-355
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• 2015

On the basis of the conventional PID control algorithm, a modified adaptive PID (MA-PID) control algorithm is presented to improve the steady-state and dynamic performance of closed-loop systems. The proposed method has a straightforward structure without excessively increasing the complexity and cost. It can adaptively adjust the values of the control parameters ($K_p$, $K_i$ and $K_d$) by following a new control law. Simulation results show that the line transient response of the MA-PID is better than that of the adaptive digital PID because the differential coefficient $K_d$ is introduced to changes. In addition, experimental results based on a FPGA indicate that the MA-PID control algorithm reduces the recovery time by 62.5% in response to a 1V line transient, 50% in response to a 500mA load transient, and 23.6% in response to a steady-state deviation, when compared with the conventional PID control algorithm.

• ETRI Journal
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• 제39권3호
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• pp.373-382
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• 2017

A new internally compensated low drop-out voltage regulator based on the cascoded flipped voltage follower is presented in this paper. Adaptive biasing current and fast charging/discharging paths have been added to rapidly charge and discharge the parasitic capacitance of the pass transistor gate, thus improving the transient response. The proposed regulator was designed with standard 65-nm CMOS technology. Measurements show load and line regulations of $433.80{\mu}V/mA$ and 5.61 mV/V, respectively. Furthermore, the output voltage spikes are kept under 76 mV for 0.1 mA to 100 mA load variations and 0.9 V to 1.2 V line variations with rise and fall times of $1{\mu}s$. The total current consumption is $17.88{\mu}V/mA$ (for a 0.9 V supply voltage).

• Journal of Power Electronics
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• 제16권6호
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• pp.2315-2326
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• 2016

This paper discusses the elimination of DC voltage deviation and the enhancement of load current sharing accuracy in multi-terminal high voltage direct current (MT-HVDC) systems. In order to minimize the power line losses in different parallel network topologies and to insure the stable operation of systems, a decentralized control method based on a modified droop control is presented in this paper. Averaging the DC output voltage and averaging the output current of two neighboring converters are employed to reduce the congestion of the communication network in a control system, and the decentralized control method is implemented. By minimizing the power loss of the cable, the optimal load current sharing proportion is derived in order to achieve rational current sharing among different converters. The validity of the proposed method using a low bandwidth communication (LBC) network for different topologies is verified. The influence of the parameters of the power cable on the control system stability is analyzed in detail. Finally, transient response simulations and experiments are performed to demonstrate the feasibility of the proposed control strategy for a MT-HVDC system.

• 한국강구조학회 논문집
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• 제12권3호통권46호
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• pp.269-279
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• 2000

차량하중의 증가 및 부식 등에 의해 손상된 강교량 구조물들은 보수 보강이 요구되어진다. 손상부채를 보수 보강하는 방법은 단면결손이 없다는 장점을 가진 용접에 의한 보수방법이 유리하다. 3차원 탄소성해석 결과를 토대로 공용중 보수용접에 의해 생기는 응력과 변형의 거동에 대해 연구하였다. 균열이 있는 부재에 하중만 작용할 경우 과도 응력의 크기는 보수용접균열길이 및 균열깊이가 큰 순으로 크다. $80MPa({\sigma}_y/3)$ 및 $140MPa({\sigma}_a)$의 응력 작용시 보수용접에 의해 발생되는 응력의 크기는 무응력 상태에서 보수용접시 발생되는 응력의 크기와 하중재하에 의해 생긴 응력의 크기의 합과 비슷하다. 응력 작용시 보수용접에 의해 발생되는 용접선방향 인장과도응력 성분은 부재폭에 대한 균열 길이비(1/b)가 커지면 커짐을 알 수 있다. 또한, 응력 작용시 보수용접에 의해 발생되는 용접선 직각방향의 면내수축변위의 크기는 보수용접길이가 긴순으로 크다.

• 전기학회논문지
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• 제58권4호
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• pp.718-724
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• 2009

Recently, Increase of energy consumption is continued accordingly because economy is constant growth. so we need long term of energy supply stability and develop new energy source. The effort of environmental improvement is necessary and our country has to educe conservatory gas in these situation, our energy policy is summarized that minimizes energy consumption and uses kinds of energy source. This paper studied some effort of stability that distributed generation put in electric system through line fault, sudden load change. And then this paper calculated penetrated level of distributed generation in system transient stability.