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

Protection system architecture for all-electric aircraft

To reduce emissions from the aviation industry and meet the targets set by different countries, research has been focused on investigating all-electric aircraft. To make this vision practical, superconducting machines are expected to power the propellers, as they are half the size and a third the weight of conventional machines. The main purpose of this paper is to do a higher-level study of a reliable holistic protection system for all-electric aircraft; that can reduce heat leakage and be able to detect faults reliably. Thus, three main protection systems were investigated; 1) cryogenic voltage source converter superconducting magnetic energy storage system (VSC-SMES), 2) cryogenic dc breaker integrated with superconducting fault current limiter (SFCL), and 3) machine learning algorithm for fault detection. By immersing the protection system at cryogenic temperature, the paper has shown that passive leakage can be eliminated, and thus more energy can be saved for the fuel cell. The paper has also demonstrated that using machine learning for the SFCL-dc-breaker system can consistently eliminate faults and protect the system

New technique for using SMES to limit fault currents in wind farm power systems

This paper introduces a new scheme, which uses a multifunctional superconducting device that can be used as an energy storage and as a fault current limiter. It is denoted as a superconducting magnetic energy storage - fault current limiter (SMES-FCL) and is modeled as a number of pancakes. It is connected to a wind turbine power system via tertiary transformer and power converters. A complete control scheme is built to achieve effective power transfer between the superconducting coil and the power system during normal operation to smooth the wind turbine output power. The fault current limiting function is implemented using a new technique that inserts a few pancakes from the whole SMES coil into the main electrical system during the fault and isolates the remaining pancakes. The number of pancakes used to limit the fault is quenched and operates as a resistive fault current limiter. The whole system including the wind turbine, the SMES-FCL model, and the interface circuit are implemented using PSCAD/EMTDC computer package. Also, the control scheme of SMES-FCL is built based on a feedback current signal to enable its operation into the two modes

Stability Improvement of DC Power Systems in an All-Electric Ship Using Hybrid SMES/Battery

As the capacity of all-electric ships (AESs) increases dramatically, the sudden changes in the system load may lead to serious problems, such as voltage fluctuations of the ship power grid, increased fuel consumption, and environmental emissions. In order to reduce the effects of system load fluctuations on system efficiency, and to maintain the bus voltage, we propose a hybrid energy storage system (HESS) for use in AESs. The HESS consists of two elements: a battery for high energy density storage and a superconducting magnetic energy storage (SMES) for high power density storage. A dynamic droop control is used to control charge/discharge prioritization. Maneuvering and pulse loads are the main sources of the sudden changes in AESs. There are several types of pulse loads, including electric weapons. These types of loads need large amounts of energy and high electrical power, which makes the HESS a promising power source. Using Simulink/MATLAB, we built a model of the AES power grid integrated with an SMES/battery to show its effectiveness in improving the quality of the power grid

Application of SMES-FCL in Electric Aircraft for Stability Improvement

The increase in aircraft passengers and airfreight traffic has given rise to concerns about greenhouse gas emissions for traditional aircraft and the resulting damage to the environment. This has led several companies and organizations, including NASA, to set goals to enhance aircraft efficiency as well as reduce fuel burn, pollution, and noise for commercial aircraft. The most notable electric aircraft (EA) concept is the N3-X, which was developed by NASA to achieve environmental goals while maintaining the annual growth of the aviation industry. However, one of the main challenges that EA is facing is their overall weight. This paper proposes and explores an improved power system architecture for use in EA, based on the N3-X concept. The number of superconducting magnetic energy storage (SMES) and fault current limiter (FCL) devices required can be reduced by utilizing multifunctional superconducting devices that combine the functionalities of both a SMES and a FCL, thus reducing the weight and cost of the EA by eliminating a complete device. The proposed control technique offers greater flexibility in determining the appropriate size of coils to function as a FCL, based on the fault type. The proposed EA power system architecture including the SMES-FCL devices is modelled in Simulink/MATLAB to test the system performance under different failure scenarios

Modelling and fault current characterization of superconducting cable with high temperature superconducting windings and copper stabilizer layer

With the high penetration of Renewable Energy Sources (RES) in power systems, the short-circuit levels have changed, creating the requirement for altering or upgrading the existing switchgear and protection schemes. In addition, the continuous increase in power (accounting both for generation and demand) has imposed, in some cases, the need for the reinforcement of existing power system assets such as feeders, transformers, and other substation equipment. To overcome these challenges, the development of superconducting devices with fault current limiting capabilities in power system applications has been proposed as a promising solution. This paper presents a power system fault analysis exercise in networks integrating Superconducting Cables (SCs). This studies utilized a validated model of SCs with second generation High Temperature Superconducting tapes (2G HTS tapes) and a parallel-connected copper stabilizer layer. The performance of the SCs during fault conditions has been tested in networks integrating both synchronous and converter-connected generation. During fault conditions, the utilization of the stabilizer layer provides an alternative path for transient fault currents, and therefore reduces heat generation and assists with the protection of the cable. The effect of the quenching phenomenon and the fault current limitation is analyzed from the perspective of both steady state and transient fault analysis. This paper also provides meaningful insights into SCs, with respect to fault current limiting features, and presents the challenges associated with the impact of SCs on power systems protection

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