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Many different applications of superconducting devices have been designed using a modular pancake arrangement. It has been reported that this modular pancake structure provides excellent mechanical holding, effective cooling, and high magnetic flux density for stability of the superconducting coil. However, soldering for interconnecting each double pancake causes current decay, cryogenic coolant loss, and thermal stress. Thus, this research investigates an improved double pancake winding, named the 'Jointless Double Pancake Coil Winding' and demonstrates the efficacy for minimizing the electrical loss of the High Temperature Superconducting (HTS) coil, assembled in the modular double pancake types. It presents a winding method that avoids soldering between the pancake connections, and thus removes the primary cause of the electrical loss generated in the existing design. This proposed winding method can effectively achieve zero electrical loss. This paper particularly presents the application of the proposed winding for the HTS-SMES and demonstrates the feasibility and improved functional benefits with reference to the conventional coil. This research should maximize the operational benefits of using the SMES coil employing the proposed winding method in charge and discharge operations, and should increase the effectiveness and efficiency in cryogenic system.

This paper proposes a systematic design procedure with comprehensive consideration of the internal and external dynamics in modular multilevel converter high voltage direct current (MMC-HVDC) transmission system. Previous studies on MMC parameter selection separately deal with each specific component such as energy storage capacity for voltage ripple of sub-module (SM) capacitor, arm inductance for second harmonic circulating current reduction, maximum allowable modulation index for MMC operating condition, which considered only a single purpose. However, the parameters respond dynamically to their characteristics and interact directly with the MMC performance, power system conditions, and specific requirements. In this study, we investigate the mutual relationships between the parameters and their performance. Then, we determine the parameter values based on a proposed systematic design procedure with the desired objectives and restricted conditions, which could be cumbersome and time-consuming to approach proper and acceptable parameter values. Therefore, this study could provide engineering evaluations and insights to help MMC-HVDC system engineers and project developers in intuitive approaches regarding the design aspects of the technology requirement challenges. The efficacy and accuracy of the analysis and design method for the MMC-HVDC system parameters were validated by PSCAD/EMTDC time-domain simulation and real-time digital simulation with hardware-in-loop system.

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