Abstract: A circular pipe member is penetrated into the seabed by a suction pressure, and a plurality of circular pipe members are vertically stacked thereon and integrated thereto to construct a cofferdam. When dismantling the cofferdam, the circular pipe members are disassembled and dismantled in order by using a lifting wire installed at a newly constructed structure installed in the inner space of the cofferdam.

Abstract: A circular pipe member is penetrated into the seabed by a suction pressure, and a plurality of circular pipe members are vertically stacked thereon and integrated thereto to construct a cofferdam. When dismantling the cofferdam, the circular pipe members are disassembled and dismantled in order by using a lifting wire installed at a newly constructed structure installed in the inner space of the cofferdam.

Abstract: The present invention relates to a voltage source converter based DC connection method and a control method for implementing a system for maintaining respective different frequencies (multi-frequencies) by reflecting load quality levels of respective microgrids when multiple stand-alone microgrids are connected to each other in which voltage source converters (VSCs) installed at connection points of the microgrids for effectively controlling respective microgrids having different frequency control ranges present an effective control method based on a concept using normalizing frequencies of unit microgrids to be similarly applied in an islanded operation mode of multiple grid-connected microgrids as well as multiple stand-alone microgrids to avoid the same frequency criterion and enable an economic operation to which the load power quality level of the microgrid is reflected, thereby minimizing a transient to stably operate a microgrid system.

Abstract: The present invention relates to a voltage source converter based DC connection method and a control method for implementing a system for maintaining respective different frequencies (multi-frequencies) by reflecting load quality levels of respective microgrids when multiple stand-alone microgrids are connected to each other in which voltage source converters (VSCs) installed at connection points of the microgrids for effectively controlling respective microgrids having different frequency control ranges present an effective control method based on a concept using normalizing frequencies of unit microgrids to be similarly applied in an islanded operation mode of multiple grid-connected microgrids as well as multiple stand-alone microgrids to avoid the same frequency criterion and enable an economic operation to which the load power quality level of the microgrid is reflected, thereby minimizing a transient to stably operate a microgrid system.

Abstract: A DC reactor consisting of a coil formed of a superconducting material is provided. It is possible to reduce leakage reactance and to increase critical current by using a coil formed of a high temperature superconducting material and forming a first bobbin of the DC reactor as a toroid shape.