• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.2
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• pp.31-41
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• 2014

This paper proposes the configuration of photovoltaic(PV) module considering the environment conditions of the PV system. The PV system is consisted of the series-parallel connection of the PV module. When shadows or changes of the radiation or an electrical characteristic in the solar cell are happened to PV system, the serious power loss will occur. If the PV module connected in series has the shadows, the output current is restricted to current of shaded PV module. Also if shadow is occurred to the parallel connection PV module, the output voltage is limited to voltage of shaded PV module. These problems are caused power loss. Therefore, this paper proposes the method that makes the output power of the PV module equalize by reconfiguration of PV module using the switching considering these environment conditions. A validity of the method proposed in this paper proves through comparing with performance of conventional PV module.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.36-44
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• 2013

This paper proposes the reconfiguration of PV module considering shadow influence of photovoltaic system. The PV system is consisted series-parallel connection of PV module. The voltage and current between PV modules become unbalance when shadow occurs to PV module. If shadow occurs to the series connection PV module, the output current is limited to current of shaded PV module. Also if shadow occurs to the parallel connection PV module, the output voltage is limited to voltage of shaded PV module. These problems are caused power loss. Therefore, the PV module in this paper consist using the fixed module and variable module by shaded conditions. The reconfiguration of PV module can compensates the shadow influence by changing connection of a variable module when shadow is occurred to PV module. A validity of the reconfiguration of PV module proposed in this paper proves through comparing with performance of conventional PV module.

• Progress in Superconductivity
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• v.6 no.1
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• pp.46-51
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• 2004

We fabricated a resistive type superconducting fault current limiter (SFCL) of 3-phase $6.6 kV_{rms}$ / rating, based on YBCO thin films grown on sapphire substrates with a diameter off inch. Each element of the SFCL was designed to have the rated voltage of $600 V_{rms}$ $/35A_{rms}$. The elements produced a single phase with 8${\times}$6 components connected in series and parallel. In addition, a NiCr shunt resistor of 23 $\Omega$ was connected in parallel to each of them for simultaneous quenches between the elements. Prior to investigating the performance of the 3 phase SFCL, we examined the quench characteristics for 8 elements connected in series. For all elements, simultaneous quenches and equal voltage distribution within 10% deviation from the average were obtained. Based on these results, performance of the SFCL for single line-to-ground faults was investigated. The SFCL successfully limited the fault current of $10 kA_{ rms}$ below 816 $A_{peak}$ within 0.12 msec right after the fault occurred. During the quench process, average temperature of all components did not exceed 250 K, and the SFCL was totally safe during the whole operation.

• Advances in Energy Research
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• v.4 no.1
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• pp.87-106
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• 2016

In this research, optimum design of the combined solar collector, geothermal heat pump and thermal seasonal storage system for heating and cooling a sample greenhouse is studied. In order to optimize the system from technical point of view some new control strategies and functions resulting from important TRNSYS output diagrams are presented. Temperatures of ground, rock bed storage, outlet ground heat exchanger fluid and entering fluid to the evaporator specify our strategies. Optimal heat storage is done with maximum efficiency and minimum loss. Mean seasonal heating and cooling COPs of 4.92 and 7.14 are achieved in series mode as there is no need to start the heat pump sometimes. Furthermore, optimal parallel operation of the storage and the heat pump is studied by applying the same control strategies. Although the aforementioned system has higher mean seasonal heating and cooling COPs (4.96 and 7.18 respectively) and lower initial cost, it requires higher amounts of auxiliary energy either. Soil temperature around ground heat exchanger will also increase up to $1.5^{\circ}C$ after 2 years of operation as a result of seasonal storage. At the end, the optimum combined system is chosen by trade-off between technical and economic issues.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.3
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• pp.354-361
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• 2014

The Unified Power Flow Controller (UPFC) can flexibly manage power flow and maintain line voltage. The UPFC consists of two inverters in parallel side and series side. In parallel side, the reactive power can be compensated to improve the power factor. In series side, the voltage drop can be compensated to maintain proper line voltage. It is necessary for the operation in both sides to output the current and the voltage quickly and accurately. As the method for the UPFC control, the deadbeat control with state observer is applied. The deadbeat control is able to realize a quick response of the current and voltage control for only a sampling period compared with the general PI control. A principle and simulation results are presented in this paper.

• Journal of the Korea Safety Management & Science
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• v.14 no.1
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• pp.225-233
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• 2012

The research discusses interrelationship of structural and reliability importance measures which used in the probabilistic safety assessment. The most frequently used component importance measures, such as Birnbaum's Importance (BI), Risk Reduction (RR), Risk Reduction Worth (RRW), RA (Risk Achievement), Risk Achievement Worth (RAW), Fussel Vesely (FV) and Critically Importance (CI) can be derived from two structure importance measures that are developed based on the size and the number of Minimal Path Set (MPS) and Minimal Cut Set (MCS). In order to show an effectiveness of importance measures which is developed in this paper, the three representative functional structures, such as series-parallel, k out of n and bridge are used to compare with Birnbaum's Importance measure. In addition, the study presents the implementation examples of Total Productive Maintenance (TPM) metrics and alternating renewal process models with exponential distribution to calculate the availability and unavailability of component facility for improving system performances. System state structure functions in terms of component states can be converted into the system availability (unavailability) functions by substituting the component reliabilities (unavailabilities) for the component states. The applicable examples are presented in order to help the understanding of practitioners.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.377-382
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• 2005

This paper presents two new circuit topologies of DC bus lineside active edge resonant snubber assisted soft-switching PWM full-bridge DC-DC converter acceptable for either utility AC 200V-rms or AC 400V-rms input voltage source. One topology of proposed DC-DC converters is composed of a typical voltage source-fed full-bridge high frequency PWM inverter using DC busline side series power semiconductor switching devices with the aid of a parallel capacitive lossless snubber. All the active power switches in the full-bridge arms and DC busline can achieve ZCS turn-on and ZVS turn-off commutations and the total turn-off switching power losses of all active switches can be reduced for high-frequency switching action. It is proved that the more the switching frequency of full-bridge soft switching inverter increases, the more soft-switching PWM DC-DC converter with a hish frequency transformer link has remarkable advantages for its efficiency and power density as compared with the conventional hard-switching PWM inverter type DC-DC converter

• Journal of Power Electronics
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• v.7 no.3
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• pp.222-232
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• 2007

This paper presents the application of a single phase AC-to-DC converter using a three-phase series parallel (SPRC) resonant converter to variable speed dc-drive. The improved power quality converter gives the input power factor unity over a wide speed range, reduces the total harmonic distortion (THD) of ac input supply current, and makes very low ripples in the armature current and voltage waveform. This soft-switching converter not only possesses the advantages of achieving high switching frequencies with practically zero switching losses but also provides full ranges of voltage conversion and load variation. The proposed drive system is the most appropriate solution to preserve the present separately excited de motors in industry compared with the use of variable frequency ac drive technology. The simulation and experimental results are presented for variable load torque conditions. The variable frequency control scheme is implemented using a DSP- TMS320LF2402. This control reduces the switching losses and current ripples, eliminates the EMI and improves the efficiency of the drive system. Experimental results confirm the consistency of the proposed approach.

• Journal of Power Electronics
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• v.7 no.3
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• pp.265-270
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• 2007

Equal rating DC-DC converter modules can be connected in series at the input for circuits requiring higher input voltages and in parallel at the output for circuits requiring higher output currents. Since the converter modules may not be practically identical, closed loop control has to ensure that each module equally shares the total input voltage and the load current. A control scheme consisting of a common output voltage loop, individual inner current loops and individual input voltage loops have been designed in this work to achieve input voltage and load current sharing as well as load voltage regulation under supply and load disturbances. The output voltage loop provides the basic reference for the inner current loops, which are also modified by the respective input voltage loops. The average of the converter input voltages, which is dynamically varying, is chosen as the reference for input voltage loops. This choice of reference eliminates interaction among different control loops. Type II compensators and Fuzzy Logic Controllers (FLCs) are designed and compared through MATLAB based simulation and FLC is found to be satisfactory. Hence TMS320F2407A DSP based FLC is implemented and the results are presented which prove the superiority of the FLC developed for this research.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.6
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• pp.390-396
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• 2021

Lithium-ion batteries have been designed and used as battery packs with series and parallel combinations that are suitable for use. However, due to its internal electrochemical properties, producing the battery's condition at the same value is impossible for individual cells. In addition, the management of characteristic deviations between individual cells is essential for the safe and efficient use of batteries as aging progresses with the use of batteries. In this work, we propose a method to manage deviation properties and detect abnormal behavior in the configuration of a combined battery pack of these multiple battery cells. The proposed method can separate and detect probabilistic low-frequency information according to statistical information based on Z-score. The verification of the proposed algorithm was validated using experimental results from 10S3P battery packs, and the implemented algorithm based on Z-score was validated as a way to effectively manage multiple individual cell information.