Investigation of HTS cable impact on turboelectric aircraft performance

With significant interest in the use of high-temperature superconducting (HTS) components in electric aircraft, there is a need for novel modelling techniques that allow architecture-level studies of the electrical systems including HTS components. In this study, a simple electric network architecture, as proposed in the literature has been considered, which includes generators, dynamic propulsion load and cables. This electric network has been modelled considering conventional technology and using HTS cables by replacing the conventional copper cables, to evaluate the variations in the network performance. The network performance has been studied for the dynamically varying propulsion load, which is nearly equivalent to the aircraft load over the entire flight duration. Following this, electric faults have been applied at various locations, and the impact of HTS cables on the network fault levels has been evaluated. The fault current levels are compared using both conventional and HTS cables, due to the fault current limiting properties of the HTS cables, they are observed to offer lowered fault current values

DC line to line short-circuit fault management in a turbo-electric aircraft propulsion system using superconducting devices

Electric aircraft has already become a reality, with demonstration flights at power ratings of less than 1 MVA. Conventional machines and distribution technologies suffer from poor power densities when scaling to large power demands, leading to significant challenges in applying this technology from small (100-seater) planes. Superconducting devices could be an enabler for electric aviation due to their great potential for high efficiency and low weight. However, while the development of the superconducting components presents a significant challenge, the safe and effective combination of such components into a propulsion system also requires a significant area of research. For this purpose, a signal-based MATLAB-Simscape model for a dc network architecture in a turbo-electric aircraft has been established and the highly nonlinear models for the superconducting devices have been developed and integrated. This network model has been used to understand the fault current magnitude and rise time, as well as the stability behavior of the system utilizing the realistic electro-thermal models of superconducting devices in it. The derived network was investigated for a bus bar short circuit fault using both superconducting fault current limiter and fault current limiting high temperature superconducting (FCL HTS) cable. Based on the network characteristics, a fault tolerant dc network design was achieved by utilizing the FCL HTS cables. Similarly, the operation limits of the protection devices have been reduced greatly using superconducting components

Utilising SMES-FCL to improve the transient behaviour of a doubly fed induction generator DC wind system

Wind energy is seen as one of the main pillars of renewable energy. However, the intermittent nature of these sources still poses as a major challenge. Moreover, sensitivity to grid faults and response to load changes are also main concerns. Superconducting devices have been introduced to solve grid faults and energy storage problems associated with renewable energy sources. Nevertheless, the cost of superconducting materials was still a major drawback for their application in power grids. In this paper, a novel power electronics circuit is used to connect the superconducting magnetic energy storage (SMES) to a DC system based on a doubly fed induction generator wind turbine. The proposed system merges energy storage function and the fault current limiting function into one device which is referred to as SMES-FCL in this paper. The role played by the SMES-FCL is studied under various scenarios that may affect the whole system. The study of the system is carried in MATLAB/SIMULINK where the system is simulated in standalone and grid-connected modes. In the end, the proposed SMES-FCL control circuit is tested in a small-scale DC system experimentally

Economic feasibility study of using high-temperature superconducting cables in U.K.'s electrical distribution networks

This paper details the key outputs of the U.K.'s first feasibility study of implementing the high-temperature superconducting (HTS) cables in electricity distribution networks to solve capacity issues. This project is mainly aimed at studying the technical and economic aspects of using superconducting cables and comparing them with the existing approaches, to determine whether a demonstration project of the superconducting solution is feasible. The University of Bath in collaboration with Western Power Distribution (WPD) has conducted this study, considering a previous capacity issue in WPD's network using both conventional and superconducting solutions. The first part of the study investigated the different aspects (installation procedures, power capacity, capital, and operational costs, etc.) of superconducting cables, comparing them with conventional cables. This identified the unique benefit of the high power density of HTS cables, which could allow the usage of a low-voltage superconducting cable in place of a high-voltage conventional cable. In the second part of the study, a 132-kV site in WPD's network that required reinforcement has been chosen for performing the feasibility study. As part of this study, a detailed cost benefit analysis (CBA) was conducted, comparing the superconducting solution with the conventional solution. The outputs from the present value analysis that has been carried out as part of the CBA are discussed. The results of the CBA power system studies performed are presented, evaluating the impact that each solution has on the network power flows, losses, and fault levels. Finally, based on the outputs from the CBA and future projections in the costs of superconducting cables, recommendations were made for the usage of superconducting cables in U.K. electricity distribution networks to solve network capacity issues

Influence of Harmonic Current on Magnetization Loss of a Tri-axial CORC REBCO Cable for Hybrid Electric Aircraft

High-temperature superconducting (HTS) triaxial conductor on round core (CORC) cable is a potential candidate for use in the transmission line of hybrid-electric aircraft because of its advantages in compactness, high power density, and reduced usage of HTS tapes. The harmonic currents generated by ac/dc converters, generators, and motors in the aircraft affect the ac loss of the transmission cable, thus influencing the efficiency of the cable. This paper analyzes the influence of harmonic current on the magnetization loss of a triaxial CORC HTS cable (10 MW, 3 kV/2 kA), which is designed for hybrid-electric aircraft. A finite element method model based on the T-A formulation has been developed for the HTS triaxial CORC cable, which calculates the losses induced both with and without applied harmonic currents. The results show that the magnetization loss has a significant nonuniform distribution among three phases even under a three-phase balanced rated load. The results also show that a small harmonic current (less than 10% of the rated load current) can lead to a considerable increase in the magnetization loss of the cable (up to 40%). In the triaxial CORC cable, harmonic currents lead to the highest increasing rate of magnetization loss with respect to frequency in the innermost phase

Effectiveness of Superconducting Fault Current Limiting Transformers in Power Systems

Superconducting devices have emerged in many applications during the last few decades. They offer many advantages, including high efficiency, compact size, and superior performance. However, the main drawback of these devices is the high cost. An option to reduce the high cost and improve the cost-benefit ratio is to integrate two functions into one device. This paper presents the superconducting fault current limiting transformer (SFCLT) as a superior alternative to normal power transformers. The transformer has superconducting windings and also provides fault current limiting capability to reduce high fault currents. The SFCLT is tested in two power system models: A 7 bus wind farm-based model simulated in PSCAD and on the 80 bus simplified Australian power system model simulated in real-Time digital simulator. Various conditions were studied to investigate the effectiveness of the fault current limiting transformer

Modelling of various rectifier flux pump topologies enabled by JcB switches

International audienceA Flux pump (FP) is a high current generating device for powering superconducting magnets. Based on their operating mechanism, they can be broadly classified into two types: dynamo FP and rectifier FP. In this paper we built the circuit models of various rectifier FP topologies, which uses DC field controlled HTS switches for the rectification purpose. The topologies are listed as: (i) half-wave retifier FP with a series resistance, (ii) half-wave rectifier FP with two switches, (iii) full- wave rectifier FP with four switches and (iv) full-wave rectifier FP with two switches. All these topologies are built within the MATLAB/Simscape platform using the predefined Ic(B) look up tables. The results show the flux pumping phenomena for various topologies using the input sinusoidal current controlled source. The modelling results from the half-wave rectifier FP model with two switches are verified against the experimental results. A feedback controlled switching methodology of the applied field switch for maximised operating efficiency is proposed for the first time in this paper. The maximum efficiency values achieved for various topologies are tabulated for comparison purpose. This models presented in this paper helps to understand the rectifier FP operating mechanism and also to optimise the FP design for the appropriate load characteristic

Modelling of various rectifier flux pump topologies enabled by JcB switches

International audienceA Flux pump (FP) is a high current generating device for powering superconducting magnets. Based on their operating mechanism, they can be broadly classified into two types: dynamo FP and rectifier FP. In this paper we built the circuit models of various rectifier FP topologies, which uses DC field controlled HTS switches for the rectification purpose. The topologies are listed as: (i) half-wave retifier FP with a series resistance, (ii) half-wave rectifier FP with two switches, (iii) full- wave rectifier FP with four switches and (iv) full-wave rectifier FP with two switches. All these topologies are built within the MATLAB/Simscape platform using the predefined Ic(B) look up tables. The results show the flux pumping phenomena for various topologies using the input sinusoidal current controlled source. The modelling results from the half-wave rectifier FP model with two switches are verified against the experimental results. A feedback controlled switching methodology of the applied field switch for maximised operating efficiency is proposed for the first time in this paper. The maximum efficiency values achieved for various topologies are tabulated for comparison purpose. This models presented in this paper helps to understand the rectifier FP operating mechanism and also to optimise the FP design for the appropriate load characteristic