• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.317-324
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• 2007

Most conventional hybrid systems using renewable energy sources have been applied for stand-alone operation, but Utility-interface may be an useful and viable option for hybrid systems. Grid-connected operation may have benefits such as reduced losses in power system distribution, utility support in demand side management, and peak load shaving. This paper addresses power control and dynamic performance of a grid-connected PV/wind/BESS hybrid system. At all times the PV way and the wind turbine are individually controlled to generate the maximum energy from given weather conditions. The battery energy storage system (BESS) charges or discharges the battery depending on energy gap between grid invertger generation and production from the PV and wind system. The BESS should be also controlled without too frequently repeated shifts in operation mode, charging or discharging. The grid inverter regulates the generated power injection into the grid. Different control schemes of the grid inverter are presented for different operation modes, which include normal operation, power dispatching, and power smoothing. Simulation results demonstrate that the effectiveness of the proposed power control schemes for the grid-interactive hybrid system.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.312-319
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• 2014

When distributed generation such as a wind power system is connected to the grid, it should meet grid requirements like IEEE Std. 1547, which regulates the anti-islanding method. Since the islanding may cause damage on electrical equipments or safety hazards for utility line worker, a distributed generation should detect it as soon as possible. This paper proposes a hybrid anti-islanding method coupled with the active and passive detection methods. To enhance the harmonic extraction capability for an active harmonic injection method, cascaded second-order band-pass filter and signal processing scheme are employed. Simulation and experiments are carried out under the islanding test condition specified in IEEE Std. 1547. Passive over/under voltage and over/under frequency methods are combined with the active method to improve the detection speed under certain condition. The simulation and experimental results are presented to verify that the proposed hybrid anti-islanding method can effectively detect the islanding.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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• pp.27-36
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• 2013

Islanding in a gird connected inverter of wind power generation system may influence a bad effect on equipments or yield safety hazards on grid so it should be detected rapidly and exactly. A passive method to detect islanding is comparatively simpler than an active method but suffers from non detection zone (NDZ). On the other hand, the active method can significantly reduce NDZ by injecting a disturbance into inverter output. To improve the reliability of islanding detection, this paper proposes a hybrid anti-islanding detection method combining the conventional passive method as well as the active method based on novel harmonic injection method using fourier transform. The proposed scheme is fast to detect islanding when NDZ does not exist because it has the nature of passive method. Under NDZ, the active method can detect occurrence of islanding reliably. The effectiveness and validity of the proposed scheme is proved through comparative simulations.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.2
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• pp.189-198
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• 2004

As display devices evolve, computer-based work environments are also becoming better suited to actual application tasks. This paper discusses the development of an architectural design system using the virtual table, which is a table-type projection system. It consists of the interactive VR modeler, the hybrid tracker and the architectural interpreter. The interactive VR modeler offers visual and tactile guide such as grid interaction, a tangible transparent prop and reference objects, so that a user can design architectural 3D models more easily and intuitively on the virtual table. The hybrid tracker includes two types of tracking methods for viewpoint according to the user's view and hand interaction: namely, vision-based tracking and magnetic tracking. The architectural interpreter automatically transforms simple 3D masses into a basic construction form that has architectural knowledge. The proposed system has advantage in the sense that it is suitable for collaboration among several users, allowing them to view graphical objects in stereoscopic view with direct 3D manipulation. Thus, it can be effectively used for architectural simulation and user-participated design.

• Journal of Power Electronics
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• v.19 no.1
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• pp.254-264
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• 2019

This paper proposes an indirect current control technique based on a proportional resonant (PR) approach for the seamless mode transfer of utility interactive inverters. Direct-current and voltage hybrid control methods have been used for inverter control under grid-connected and islanded modes. A large bandwidth can be selected due to the structure of single-loop control. However, this results in poor dynamic transients due to sudden changes of the controller during mode changes. Therefore, inverter control based on indirect current is proposed to improve the dynamic transients by consistently controlling the output voltage under all of the operation modes. A PR-based indirect current control topology is used in this study to maintain the load voltage quality under all of the modes. The design processes of the PR-based triple loop are analyzed in detail while considering the system stability and dynamic transients. The mode transfer techniques are described in detail for both sudden unintentional islanding and islanded mode voltage quality improvements. In addition, they are described using the proposed indirect control structure. The proposed method is verified by the PSiM simulations and laboratory-scale VDER-HILS experiments.