Predicting the output power of wind generators is essential to improve grid flexibility, which is vulnerable to power supply variability and uncertainty. Digital twins can help predict the output of a wind turbine using a variety of environmental data generated by real-world systems. This paper dealt with the development of a physics-based output prediction model (P-bOPM) for a 10 MW floating offshore wind turbine (FOWT) for a digital twin. The wind power generator dealt with in this paper was modeled considering the NREL 5 MW standard wind turbine with a semi-submersible structure. A P-bOPM of a 10 MW FOWT for a digital twin was designed and simulated using ANSYS Twin Builder. By connecting the P-bOPM developed for the digital twin implementation with an external sensor through TCP/IP communication, it was possible to calculate the output of the wind turbine using real-time field data. As a result of evaluating the P-bOPM for various marine environments, it showed good accuracy. The digital twin equipped with the P-bOPM, which accurately reflects the variability of the offshore wind farm and can predict the output in real time, will be a great help in improving the flexibility of the power system in the future.

This paper deals with the possibility of applying superconducting motors and hydrogen fuel cells to electric aviation propulsion systems (APS) for the development of next-generation APS. Instead of the conventional fossil fuel-based power generation system, the APS using hydrogen fuel cells and superconducting motors was conceptually designed. The proposed APS consists of a superconducting motor, a hydrogen fuel cell, a liquid hydrogen tank, and a battery. For specific power comparison, the proposed APS capacity was the same as that of a commercial APS, and the capacity and weight of the hydrogen fuel cell and battery were calculated. The 5 MW superconducting motor was designed and analyzed focusing on magnetic field distribution, thermal load, mechanical stress, efficiency, weight, and specific power. As a result, the proposed APS is expected to reach the level of performance applicable to aircraft in the near future, given the recent development trend of battery and liquid hydrogen technology. These results are expected help in a future-oriented APS design.

As the demand for eco-friendly energy increases, hydrogen energy and liquid hydrogen storage technologies are being developed as an alternative. Hydrogen has a lower liquefaction point and higher thermal conductivity than nitrogen or neon used in general cryogenic systems. Therefore, the application of hydrogen to cryogenic systems can increase efficiency and stability. This paper describes the design and analysis of a cryogenic cooling system for an electric propulsion system using liquid hydrogen as a refrigerant and energy source. The proposed aviation propulsion system (APS) consists of a hydrogen fuel cell, a battery, a power distribution system, and a motor. For a lab-scale 5 kW superconducting motor using a 2G high-temperature superconducting (HTS) wire, the HTS motor and cooling system were analyzed for electromagnetic and thermal characteristics using a finite element method-based analysis program. The liquid hydrogen-based cooling system consists of a pre-cooling system, a hydrogen liquefaction system, and an HTS coil cooling system. Based on the thermal load analysis results of the HTS coil, the target temperature for hydrogen gas pre-cooling, the number of buffer layers, and the cryo-cooler capacity were selected to minimize the thermal load of the hydrogen liquefaction system. As a result, the hydrogen was stably liquefied, and the temperature of the HTS coil corresponding to the thermal load of the designed lab-scale HTS motor was maintained at 30 K.

This paper presented a comparison study result on the design of direct-driven type superconducting wind power generators using MgB2 and YBCO wires. Detailed features of MgB2 and YBCO wires were investigated and 4 MW superconducting generators were designed using MgB2 and YBCO wires. The magnetic field distributions of the generators were analysed using a 3D finite element method program. The total length of the wires, the volume, and weight of the designed generators were compared. As a result, the weight and volume of the generator using the YBCO wire were lighter and smaller than the generator using the MgB2 wire. The required length of the MgB2 was shorter than the YBCO wire which is much more expensive than MgB2 wire. It is therefore necessary to select the appropriate superconducting wires considering cost, weight, and volume issues when designing superconducting generators.

Large-capacity superconducting power cables are in the spotlight to replace existing underground transmission power cables for energy power transmission. Among them, the three-phase coaxial superconducting power cable has the economic advantage of reducing the superconducting shielding layer by enabling magnetic shielding when the three phases are homogeneous without an independent superconducting shielding layer for magnetic shielding. In order to develop the three-phase coaxial superconducting power cable, the electrical and structural design should be carried out to construct the superconducting layer. However, the thermal design and analysis for the cooling of the three-phase coaxial superconducting power cable must be done first, so that the electrical design can be made using the temperature transferred to the superconducting layer. The three-phase coaxial superconducting cable requires a cooling system to circulate the cryogenic refrigerant for cooling below a certain temperature, and the structure of the cable through which the cryogenic refrigerant travels must also be analyzed. In this paper, the authors conducted a longitudinal temperature analysis according to the structure of the refrigerant circulation system of the cable and proposed a refrigerant circulation system suitable for this development. The temperature profile according to this analysis was then used as a function of temperature for the electrical (superconducting and insulating layers) design of the three-phase coaxial superconducting power cable. It is also expected to be used to analyze the cooling structure of the three-phase coaxial superconducting power cable installed in the real grid system.

This paper presents the results of an electromagnetic design and numerical analysis conducted on a 10-MW-class second-generation high-temperature superconducting generator (2G HTSG) used in an offshore wind power turbine. To report the operation reliability of 10-MW-class HTSGs employed in off-shore environment, various electric insulation techniques (EITs) for HTS field coils (FCs), such as no-insulation, metal insulation, and metal-insulator transition insulation, are considered in this study. Using the time-transient solver of the three-dimensional (3D) electromagnetic finite element analysis (FEA), we investigated the electromagnetic characteristics of the HTSG with the three EITs in terms of the electrical output of the HTSG and the critical current of the FCs. To analyze the charging characteristic of the HTS FCs with the three EITs in steady-state operation as well as the electrical in transient-state operation, electric equivalent circuit models are built with key parameters based on the electromagnetic FEA results. Finally, the performances of the HTS FCs are discussed and evaluated in terms of the electromagnetic response and stability characteristics.