• Journal of Navigation and Port Research
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• v.31 no.3 s.119
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• pp.229-233
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• 2007

This paper presents the performance of PV(Photovoltaic) system, the design of MPPT(Maximum Power Point Tracker). Output of PV power system is DC, and PV power system is linked to the DC bus. The current(I)-voltage(V) output characteristic of PV cells changes with solar irradiance and cell temperature as parameters. As various PV modules respond differently to each of the parameters cited above. Maximum output of PV modules am be achieved by MPPT(Maximum Power Point Tracker) algorithm This paper includes a discussion on the performance of PV module, MPPT algorithm and the influence of PV module angle.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.158-163
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• 2005

Competitive electricity markets necessitate equitable methods for allocating transmission usage in order to set transmission usage charges and congestion charges in an unbiased and an open-accessed basis. So in competitive markets it is usually necessary to trace the contribution of each participant to line usage, congestion charges and transmission losses, and then to calculate charges based on these contributions. A UPFC offers flexible power system control, and has the powerful advantage of providing, simultaneously and independently, real-time control of voltage, impedance and phase angle, which are the basic power system parameters on which sys-tem performance depends. Therefore, UPFC can be used efficiently and flexibly to optimize line utilization and increase system capability and to enhance transmission stability and dampen system oscillations. In this paper, a mathematical approach to allocate the contributions of system users and UPFCs to transmission system usage is presented. The paper uses a dc-based load flow modeling of UPFC-inserted transmission lines in which the injection model of the UPFC is used. The relationships presented in the paper showed modified distribution factors that modeled impact of utilizing UPFCs on line flows and system usage. The derived relationships show how bus voltage angles are attributed to each of changes in generation, injections of UPFC, and changes in admittance matrix caused by inserting UPFCs in lines. The relationships derived are applied to two test systems. The results illustrate how transmission usage would be affected when UPFC is utilized. The relationships derived can be adopted for the purpose of allocating usage and payments to users of transmission network and owners of UPFCs used in the network. The relationships can be modified or extended for other control devices.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.205-213
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• 2002

This paper deals with the implementation of three-phase VSI systems which can control the power regenerated from DC bus line to AC supply. The overall system consists of the line-to-line voltage and line current sensors, an actual power calculator using d-q transformation method, a complex power controller with PI control scheme, a gating signal generator for modified ｑ-conduction mode, a DPLL for frequency followup, and Power circuits. Control board is constructed by using a 32-bit DSP TMS32C32, two EFLDs , six ADCs, and a DAC. To verify the performance of the proposed system, we designed and constructed the propotype with the power rating of 5kVA at AC 220V. Experimental results show that the regenerated active power is well controlled to its command vague and the regenerated reactive power still remained at nearly zero through all operating modes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.3
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• pp.74-83
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• 2002

The maximun short circuit current of modern power system is becoming so large that circuit breaker is not expected to be able to shut down the current in the future In order cut over-currents, a system composed of a superconducting fault current limiter(SFCL) and traditional breaker seems to provide a promising solution for furture power operation. In present paper, three line-to-ground fault is assumed to happen at the center of 345kV transmission lines in a large capacity electric power system. The superconducting fault current limiter was represented using a commutation type, which consists of a non-inductive superconducting coil and current limiting element (resistor or reactor). from the viewpoint of current limiting performance, the prevention of the voltage drop at the load bus and comparision characteristics for two type SFCL. Desired design specification and operation parameters of SECL were also given qualitatively by the performance.

• KIPS Transactions on Computer and Communication Systems
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• v.10 no.7
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• pp.199-204
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• 2021

Digital substation refers to a substation that digitizes functions and communication methods of power facilities such as monitoring, measuring, control, protection, and operation based on IEC 61850, an international standard for the purpose of intelligent power grids. Based on the intelligent operating system, efficient monitoring and control of power facilities is possible, and automatic recovery function and remote control are possible in the event of an accident, enabling rapid power failure recovery. With the development of digital technology and the expansion of the introduction of eco-friendly renewable energy and electric vehicles, the spread of direct current distribution systems is expected to expand. MVDC is a system that utilizes direct current lines with voltage levels and transmission capacities between HVDCs applied to conventional transmission systems and LVDCs from consumers. Converting existing lines in substations, where most power equipment is alternating current centric, to direct current lines will reduce transmission losses and ensure greater current capacity. The process bus of a digital substation is a communication network consisting of communication equipment such as Ethernet switches that connect installed devices between bay level and process level. For MVDC linkage to existing digital substations, the process level was divided into two buses: AC and DC, and a system that can be comprehensively managed in conjunction with diagnostic IEDs as well as surveillance and control was proposed.