• The Transactions of the Korean Institute of Power Electronics
• /
• v.19 no.3
• /
• pp.201-210
• /
• 2014

In this paper, dc-link voltage control of a grid-connected QZSI is presented. Since the input current of the ZSI is discontinuous, a capacity with relatively large capacitance should be connected to the output of the PV array in order to reduce the current ripple. Due to the presence of the impedance network inductor in series with the PV array, the QZSI can achieve continuous input current flow. Several dc-link voltage control methods are compared and the method for power quality improvement is also presented. The performance of the proposed method is verified through both simulation and experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.8
• /
• pp.5400-5405
• /
• 2014

For the development of a floating photovoltaic system, materials with light weight and high tensile strength must be applied to reduce the burden on buoyancy, and material characteristics with high resistance to corrosion in water environment is required. Accordingly, a new high strength steel material with improved strength, durability, manufacturability, and weldability that are appropriate for floating photovoltaic system structures is needed. This paper reports the results of a mechanical load test and steel corrosion test on general steel (SS400) and high strength steel (POSH 690) for the selection of an appropriate steel material for a floating photovoltaic system. The results of a test on new high strength steel revealed excellent mechanical performance compared to general steel. The new steel material was manufactured for use in an actual site, and the weight was reduced by approximately 30~40% compared to existing general steel.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.19 no.5
• /
• pp.181-186
• /
• 2019

In order to reduce the fossil fuels consumed in conventional commercial independent diesel generators in the same environment as the island area, it is necessary to develop a photovoltaic system that will bear more than 40% of the independent system capacity. For this development, it is necessary to develop a high-capacity inverter that can improve the stability of the independent system installed in the island area and supply high-quality power to the load. In addition, the EMS power generation control system for the independent grid photovoltaic power generation system is a parallel operation power control system of the diesel generator connected with the solar power generation system. It controls the output of the diesel generator according to the load ratio and the solar power generation, A stable supply system is needed. This independent grid photovoltaic generation system can increase the solar power supply to the independent system area and increase the power stability of the independent system and further reduce the use of fossil fuel due to the ineffective power control of the independent system. It is expected that the economy will be secured early.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.5
• /
• pp.712-716
• /
• 2013

In solar generation, the PV array's azimuth is headed due south and the tilt is generally $33^{\circ}$ in order to acquire maximum generation. However, when installed in a site where there are buildings or other facilities, the azimuth and tilt are adjusted. Yet, when the azimuth and tilt are deviated from due south and $33^{\circ}$, the generation quantity is decreased substantially and currently a method to estimate the decreasing proportion is unavailable. Therefore, in this thesis, an equation on the "change ratio of solar radiation due to the changes in tilt and azimuth" was deduced by utilizing empirical data on the amount of solar radiation received according to the changes of tilt and azimuth and Interpolation. By using this equation, the decreasing proportion of generating quantity due to the installation methods of PV system can be estimated, therefore, it can be usefully utilized when designing and going through feasibility studies for development of solar generation systems.

• Journal of Power Electronics
• /
• v.16 no.2
• /
• pp.654-665
• /
• 2016

The pumping of electric power from photovoltaic (PV) farms is normally carried out using transformers, which require heavy mounting structures and are thus costly, less efficient, and bulky. Therefore, transformerless schemes are developed for the injection of power into the grid. Compared with the H4 inverter topology, the H6 topology is a better choice for pumping PV power into the grid because of the reduced common mode current. This paper presents how the perturb and observe (P&O) algorithm for maximum power point tracking (MPPT) can be implemented in the H6 inverter topology along with the improved sinusoidal current injected to the grid at unity power factor with the average current mode control technique. On the basis of the P&O MPPT algorithm, a power reference for the present insolation level is first calculated. Maintaining this power reference and referring to the AC sine wave of bus bars, a sinusoidal current at unity power factor is injected to the grid. The proportional integral (PI) controller and fuzzy logic controller (FLC) are designed and implemented. The FLC outperforms the PI controller in terms of conversion efficiency and injected power quality. A simulation in the MATLAB/SIMULINK environment is carried out. An experimental prototype is built to validate the proposed idea. The dynamic and steady-state performances of the FLC controller are found to be better than those of the PI controller. The results are presented in this paper.

• Journal of Power Electronics
• /
• v.16 no.5
• /
• pp.1629-1638
• /
• 2016

Differential power processing (DPP) systems are among the most effective architectures for photovoltaic (PV) power systems because they are highly efficient as a result of their distributed local maximum power point tracking ability, which allows the fractional processing of the total generated power. However, DPP systems require a high-efficiency, high step-up/down bidirectional converter with broad operating ranges and galvanic isolation. This study proposes a single, magnetic, high-efficiency, high step-up/down bidirectional DC-DC converter. The proposed converter is composed of a bidirectional flyback and a bidirectional isolated switched-capacitor cell, which are competitively cheap. The output terminals of the flyback converter and switched-capacitor cell are connected in series to obtain the voltage step-up. In the reverse power flow, the converter reciprocally operates with high efficiency across a broad operating range because it uses hard switching instead of soft switching. The proposed topology achieves a genuine on-off interleaved energy transfer at the transformer core and windings, thus providing an excellent utilization ratio. The dynamic characteristics of the converter are analyzed for the controller design. Finally, a 240 W hardware prototype is constructed to demonstrate the operation of the bidirectional converter under a current feedback control loop. To improve the efficiency of a PV system, the maximum power point tracking method is applied to the proposed converter.

• Journal of the Korean Solar Energy Society
• /
• v.29 no.2
• /
• pp.8-13
• /
• 2009

In this paper, two configurations of PV array are analyzed and tested under shading condition, where two configurations are series-parallel and total-crass-tied configuration. Each photovoltaic module is emulated by two 5 inch po1y-crystalline cells in series and an array is constructed by connecting 24 of the modules to compare a generated maximum power of the two configurations. Pspice and Sun simulator. PASAN IIIb, are used for simulation and experiment to test the array under various partial shading conditions. Test results show the total-cross-tied configuration generates 7.63% higher maximum power than the series-parallel configuration, and it is well matched to the analysis and simulations of the two configurations.

• 한국태양에너지학회:학술대회논문집
• /
• 2009.11a
• /
• pp.155-160
• /
• 2009

The increasingly high prices for oil, the exhaustion of fossil fuels as well as concern about global warming are driving rapid growth of alternative sources of energy in the world. The active solution for global environment and exhaustion of energy sources is to develop and popularize the technologies to use natural energy such as sunlight, wind, and water. PV(Photovoltaic) modules are efficient devices that has been considered a logical material for use in buildings. Recent advanced BIPV(Building Integrated PV) technology have rapidly made PVs suitable for direct integration into construction in the world. Recently, building has been higher and higher. Tall buildings have many advantages for BIPV such as wide facade area and no shading effect by the surrounding buildings. However. BIPV has not been applied for tall building facade yet. Therefore, the purpose of the research is to develop suitable BIPV for tall buildings and to put these technologies to practical use. Therefore, the purpose of the study is to investigate unification of BIPV to curtain wall to apply BIPV on tall building through research into advanced application of overseas BIPV cases.

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.4
• /
• pp.190-194
• /
• 2017

Present-day solar panels incorporate inverters as their core components. Switching devices driven by specialized power controllers are operated in a transformerless inverter topology. However, some challenges associated with this configuration include the absence of isolation, causing leakage currents to flow through various components toward ground. This inevitably causes power losses, often being also the primary reason for the power inverters' analog equipment failure. In this paper, various aspects of the leakage currents are studied using different circuit analysis methods. The primary objective is to convert the leakage current energy into a usable DC voltage source. The research is focused on harvesting the leakage currents for producing circa 1.1 V, derived from recently developed rectifier circuits, and driving a $200{\Omega}$ load with a power in the milliwatt range. Even though the output voltage level is low, the harvested power could be used for charging small batteries or capacitors, even driving light loads.

• Proceedings of the KIEE Conference
• /
• 2005.07b
• /
• pp.1705-1707
• /
• 2005

This paper proposes a novel active frequency drift(AFD) method for the islanding prevention of grid-connected photovoltaic inverter. To detect the islanding phenomenon of grid-connected photovoltaic(PV) inverters concerning about the safety hazards and the damage to other electric equipments, many kinds of anti-islanding methods have been presented. Among them, AFD method using chopping fraction(cf) enables the islanding detection to drift up(or down) the frequency of the voltage during the islanding situation. However, the performance of the conventional AFD methods, which have a certain value of cf only, is inefficient and difficult to design the appropriate cf value analytically to meet the limit of harmonics. In this paper, the periodic chopping fraction based on an AFD method is proposed. This proposed method shows the analytical design value of cf to meet the test procedure of IEEE Std. 929-2000 with the power quality and islanding detection time. To verify the validation of the proposed method, the islanding test results are presented. It is confirmed that the proposed method has not only less harmonic distortion but also good performance of islanding detection compare with the conventional AFD method.