Superconducting Magnetic Energy Storage Magnet Research Articles

The Influence of SMES Magnet Operation Parameters on Voltage Distribution Characteristic

The voltage distribution on the magnet of superconducting Magnetic Energy Storage (SMES) system are the result of the combined effect of system power demand, operation control of power condition system (PCS) and magnet parameters, which is a key issue that influence the stability and security of SMES magnet. This paper mainly focuses on the interaction between the different components and the influence factors on voltage distribution on the magnet. Firstly, the hybrid model which integrate the power system dynamics, the detailed device of PCS and the transient model of magnet is built. Then, from the perspective of power requirement of power system, operation mode and control strategy of PCS, the voltage distribution characteristics are comprehensively analyzed. Finally, the optimization design method of operation mode to reduce the unevenness of voltage distribution is proposed.

An approach to development of the HTS magnet for SMES at JINR

Particle accelerator complex NICA (Nuclotron-based Ion Collider fAcility) comprises superconducting Booster and Nuclotron synchrotrons which magnets operating at pulse mode in opposite phase with period of about 4 seconds. Summary stored energy of Booster and Nuclotron magnets will vary from 1 to 2.6 MJ during the period. NICA power supply system can be significantly improved by Superconducting Magnetic Energy Storage (SMES) application that will help to move the energy back and force between Booster and Nuclotron. The useful energy at this SMES must be about 1.6 MJ so the maximum total SMES energy should be 3-5 MJ. SMES with this energy should have several Tesla magnetic fields to keep a reasonable size. SMES operating current can be not less than Booster and Nuclotron magnets current so it might be 10-12 kA. It is better to make such a SMES magnet from an HTS (high temperature superconductor) cable for the stability at 6-7 T and 4 s pulse mode. The SMES magnet is planned to be wound as a short solenoid (Brooks coil) of cables optimized for several coaxial sections. HTS cables with helical structure similar to well-known CORC (conductors on round core) cables are under the development at JINR. The HTS cabling technology is based on the same principle as Nuclotron type cable manufacturing technology. HTS tapes, cables and magnets experimental study and testing methods are being developed on the base of an existing test facility at LHEP. First HTS cable short sample with 6 HTS tapes was prepared and tested at 77 K in self-field. Its critical current is about 800 A that will allow achieve required operating currents of SMES magnet with a reasonable amount of HTS tapes in cables. Developments of high field high current fast cycling HTS magnets for accelerators are also being planned at JINR.

Electro-Magnetic Design of a 3MJ YBCO Magnet

The electro-magnetic design of two 3 MJ superconducting magnetic energy storage (SMES) magnets with YBCO conductor are presented. One magnet is with solenoidal geometry composed of double pancake coils, and the other one is with toroidal geometry. According to the magnetic field simulation results, the perpendicular componet of the magnetic field of the toroidal magnet could be extremely reduced compared with the solenoidal geometry. Therefore, a lower YBCO conductor requirement could be expected due to the dependence of Jc vs B performance of the YBCO conductor. Besides, the lower leakage magnetic field is important for application. A SMES system of 3 MJ is considered, and the coil is made of multiple identical D-type pancake coils. The critical current of the used YBCO conductor at 30K is 270A under 1 T perpendicular magnetic field. The inner radius of the D-type curve is 500 mm, and the outer radius is 1000 mm. The SMES magnet is made of 96 pancake coils, where the rated operating current is 975 A and the maximum perpendicular and parallel magnetic flux density are 0.5 T and 4.0 T, respectively. Further more, the maximum hoop stress and radial stress are 283 MPa and 78 MPa.

Integrated design method for superconducting magnetic energy storage considering the high frequency pulse width modulation pulse voltage on magnet

Superconducting magnetic energy storage (SMES) is composed of three main components, which are superconducting magnet, power conditioning system (PCS), and system controller to fulfil the task of power exchange between the power system and SMES. In addition to the basic design of single component, the interaction between different components of SMES should be considered during the design process. Firstly, the dynamic power compensation has effect on the losses of SMES magnet, which should be considered in the magnet design. Secondly, the dynamic response characteristic of PCS influences the power response capability of SMES. Thirdly, the high frequency pulse width modulation (PWM) pulse voltage generated by the PCS and applied directly to the SMES magnet could induce insulation issues of the magnet, which is the key factor of ensuring the security of the magnet. Considering the mutual effect of SMES components comprehensively, an integrated design method for SMES system is proposed in this paper. To evaluate the effectiveness of the proposed integrated design method, a 3.8 MJ/1.2 MW SMES system applied in a micro grid is designed comprehensively.

Enhancing Transient Voltage Quality in a Distribution Power System With SMES-Based DVR and SFCL

Conceptual design and performance evaluation of a voltage sag compensation scheme based on the superconducting fault current limiter (SFCL) and a MW-class dynamic voltage restorer (DVR) system integrated with superconducting magnetic energy storage (SMES) are presented and investigated. A pre-sag compensation strategy is introduced to lock the instantaneous magnitudes and phase angles of real-time line voltages for compensating the improper voltage components completely. A 0.3-H/1.76-kA SMES magnet is structurally designed for MW-class power exchange operations, and the SFCL's resistance is also estimated in detail. Various simulation cases with regard to voltage sag are carried out. The simulations have demonstrated that the proposed voltage sag compensation scheme is able to maintain the stabilizations of root-mean-square voltages, and mitigate the adverse effects of voltage sag on sensitive load. Furthermore, the compensated power injected to sensitive load by DVR is decreased owing to the additional voltage improvement provided by SFCL, thereby reducing the total capital costs of DVR.

Numerical analysis on 10 MJ solenoidal high temperature superconducting magnetic energy storage system to evaluate magnetic flux and Lorentz force distribution

Due to fast response and high energy density characteristics, Superconducting Magnetic Energy Storage (SMES) can work efficiently while stabilizing the power grid. The challenges like voltage fluctuations, load shifting and seasonal load demands can be accomplished through HTS magnet as this device has a great potential to supply power for a time span varies from few seconds to hours. Solenoidal configuration has been widely employed (over toroidal) in the development of SMES prototypes as it is simpler to manufacture and allows an easier handling of the mechanical stresses imposed on the structure due to Lorentz forces. A micro-SMES of capacity 10 MJ can be employed to mitigate the challenges like load leveling, dynamic stability, transient stability, voltage stability, frequency regulation, transmission capability enhancement, power quality improvement, automatic generation control, uninterruptible power supplies, etc.In this work, solenoidal configuration has been engaged in the development of 10 MJ SMES Magnet using 2 G (SuperPower, YBCO having Tc = 90 K @0T) High Temperature Superconducting (HTS) tape. The superconducting tape has been cooled at 14 K using conduction cooling. The effect of maximum operating current (3250A, 2600A, 1950A and 1300A) on the inductance, maximum storable energy and length of superconductor has also been evaluated for a constant deliverable energy of 10 MJ. A numerical analysis is done on 10 MJ HTS SMES where perpendicular field of 3T has been considered. The effect of aspect ratio (solenoidal height to bore diameter ratio) on the normal component of the magnetic field has also been assessed. Lorentz forces (N/m3) have been evaluated in the superconducting domain. It has been concluded that it would be beneficial to operate at higher currents (i.e. more current through single tape) as it can reduce the total length of the superconductor. The perpendicular component of magnetic flux for the analysis is found to 2.96T which is less than 3T.

SMES-Battery Energy Storage System for the Stabilization of a Photovoltaic-Based Microgrid

As superconducting magnetic energy storage (SMES) and battery are complementary in their technical properties of power capacity, energy density, response speed, etc., this paper proposes an SMES-battery energy storage system to stabilize a photovoltaic-based microgrid under different faults. The related theoretical modeling is stated, and the control and coordination methods of the SMES-battery are put forward. Using MATLAB, a comparison of with the SMES-battery and only with the battery is carried out. From the main specifications of the SMES magnet, the ac-loss calculation is also performed. The results show that i) the SMES-battery is better than the battery to timely deal with the transient faults of the microgrid; ii) the SMES-battery enables to ensure a seamless mode-transition for the microgrid under the external fault, and reduce the fault current in the point of common coupling to avoid an unnecessary off-grid under the internal fault; and iii) the SMES magnet's ac-loss power has a maximum value of 380 W, and it is acceptable for the future design of conduction-cooled structure and cryogenic system.

Analysis of the loss and thermal characteristics of a SMES (Superconducting Magnetic Energy Storage) magnet with three practical operating conditions

The losses of Superconducting Magnetic Energy Storage (SMES) magnet are not neglectable during the power exchange process with the grid. In order to prevent the thermal runaway of a SMES magnet, quantitative analysis of its thermal status is inevitable. In this paper, the loss characteristics of a self-developed 150 kJ SMES magnet are analyzed by means of experiments and simulations, including the loss of the joint resistance, the eddy current loss of the metal cooling structures and the AC loss of the superconducting magnet. A thermal model of the magnet was built to theoretically analyze the relationship between the current and magnet temperature variation. Three kinds of power compensation experiments were carried out to study the thermal characteristics of the SMES magnet. The temperature variation of the magnet under these three operating conditions was simulated. The simulation results and experimental results are compared and analyzed.

Design and Evaluation of a Mini-Size SMES Magnet for Hybrid Energy Storage Application in a kW-Class Dynamic Voltage Restorer

This paper presents the design and evaluation of a mini-size GdBCO magnet for hybrid energy storage (HES) application in a kW-class dynamic voltage restorer (DVR). The HES-based DVR concept integrates with one fast-response high-power superconducting magnetic energy storage (SMES) unit and one low-cost high-capacity battery energy storage (BES) unit. Structural design, fabrication process, and finite-element-modeling simulation of a 3.25 mH/240 A SMES magnet wound by state-of-the-art GdBCO tapes in SuNAM are presented. To avoid the internal soldering junctions and enhance the critical current of the magnet simultaneously, an improved continuous disk winding (CDW) method is proposed by introducing different gaps between adjacent single-pancake coil layers inside the magnet. About 4.41% increment in critical current and about 3.42% increment in energy storage capacity are demonstrated compared to a conventional CDW method. By integrating a 40 V/100 Ah valve-regulated lead-acid battery, the SMES magnet is applied to form a laboratory HES device for designing the kW-class DVR. For protecting a 380 V/5 kW sensitive load from 50% voltage sag, the SMES unit in the HES-based scheme is demonstrated to avoid an initial discharge time delay of about 2.5 ms and a rushing discharging current of about 149.15 A in the sole BES-based scheme, and the BES unit is more economically feasible than the sole SMES-based scheme for extending the compensation time duration.

Implementing dynamic evolution control approach for DC-link voltage regulation of superconducting magnetic energy storage system

A Dynamic Evolution Control (DEC) scheme for the Superconducting Magnetic Energy Storage (SMES) system is presented in this article. The DC-link voltage of Power Converter Unit (PCU) is strictly regulated by the proposed control scheme irrespective of load transients. In SMES system, the PCU interfaces the SMES magnet and the AC system in order to give an efficient power exchange, and high quality power flow in the grid. Especially, this paper focuses on power quality improvement, and homogeneous voltage distribution & AC loss reduction across the magnet by achieving excellent DC-link voltage regulation. The harmonic components of magnet current are analyzed which are responsible for AC losses. It has been observed that the 3rd, 4th, 5th, 6th and 7th order harmonic components of the magnet current are significantly reduced. Particularly, a homogeneous voltage profile and less distorted magnet current are attained using the control scheme. The system supply current is found almost balanced, and its Total Harmonic Distortion (THD) is found well below 5%. Moreover, the control performance of DEC scheme is compared with that of the Proportional-Integral (PI) control technique. The proposed system is validated both in MATLAB/SIMULINK and real-time environment using a digital signal processor (dSPACE1104).

AC Loss Analysis of a Hybrid HTS Magnet for SMES Based on <italic>H</italic>-Formulation

AC loss is an unavoidable problem for a conduction-cooled HTS superconducting magnetic energy storage (SMES) magnet during dynamic operation, which may cause a temperature raise and affect the reliable operation of the magnet. In this paper, the anisotropic homogenization method is employed to realize the modeling of a 150 kJ hybrid SMES magnet based on H-formulation. The SMES magnet has a maximum of approximately 7000 turns. First, the homogenization method is validated that it can reasonably predict the ac losses of both YBCCO coils and BSCCO coils, but it has lower accuracy to estimate the ac losses of BSCCO coils than YBCO coils. Then, ac loss characteristics of the SMES magnet during dynamic operations are investigated. The magnetic field, current density distribution, and ac loss distribution are presented and discussed for different operation conductions. The results indicate that a steady-state current of less than 100 A may be an appropriate choice during power exchange for reducing ac loss.

Mechanical Properties of MJ-Class Toroidal Magnet Wound by Composite HTS Conductor

An MJ-class superconducting magnetic energy storage (SMES) system has a wide range of potential applications in electric power systems. The composite high-temperature superconducting HTS conductor, which has the advantages of carrying large critical currents and withstanding high magnetic fields, is suitable for winding an MJ-class magnet coil. However, the Lorentz force of an HTS wire is so large that its induced mechanical stresses should be examined to ensure that the magnet is in good condition. By means of the equivalent material properties method and the sequential coupling method, this paper studies the mechanical properties of a three MJ toroidal SMES magnet wound by a composite HTS conductor. Based on the electromagnetic-structural coupling analysis, the Von-Mises stress, the radial stress, and the hoop stress of a magnet coil are calculated and employed to validate the stability of the MJ-class toroidal SMES magnet.

Constant Field Toroidal SMES Magnet

The Massachusetts Institute of Technology has been performing a preliminary study of superconducting magnetic energy storage (SMES) magnet configurations under a Pole MecaTech Cluster collaboration sponsored by the government of the Walloon Region in Belgium. Consortium members include Ion Beam Applications S.A. (IBA), CE+T Power (CE+T), Euro-Diesel S.A. (Euro-Diesel), Jema S.A. (JEMA), the University of Liege (ULG), the Catholic University of Louvain-la-Neuve (UCL), and the Liege Space Center (CSL). The goal of the project was to assess the commercial feasibility of various SMES magnet configurations by evaluating specific energy, magnetic field shielding properties, and manufacturing cost. Among the examined configurations, the constant field toroid (CFT) attracted our attention, and it is the subject of this paper. The present study presents the description of the magnetic design algorithm and an example of the first-level optimization of the stored and specific energy. Numerical simulations are performed using Cobham Opera. A procedure of a simplified analytical optimization of a magnet system is used to maximize the stored energy or the specific energy (per unit weight of the conductor) of a CFT magnet.

A Universal LabVIEW-Based HTS Device Measurement and Control Platform and Verified Through a SMES System

This paper presents a computer-controlled test platform for superconducting magnetic energy storage (SMES) control and measurement based on the Laboratory Virtual Instrument Engineering Workbench (LabVIEW). The purpose is to achieve the fast control and friendly measurement simultaneously by integrating the LabVIEW and commercial digital control chips. The test platform mainly consists of three modules, i.e., power conditioning system (PCS) module, control module and measurement module. The PCS module imitates the operational conditions and characteristics of a practical SEMS device by using the combination of a programmable power source and an equivalent load network. A LabVIEW-based program is also designed to output various imitated charge-discharge current waveforms to directly supply the SMES magnet so as to avoid the use of the complicated and costly practical PCS. The measurement module has multi-functions of current-voltage (I-V), temperature and magnetic field measurements. In cooperation with the control module, the measured data are applied to adjust the real-time operational state of the PCS module and to protect the SMES magnet when the quench is detected. The test platform has been experimentally verified for the use in a small-scale SMES prototype.

Numerical Simulation of Coupled Heat Transfer, Stress, and Electromagnetic Properties in an SMES Magnet

This paper describes the analysis procedure and FEM model considering the parallel effects of stress and thermal problem coupled with the electromagnetic field problem of a 10 MJ Superconducting Magnetic Energy Storage (SMES) magnet. Since the coupled processes in most analyses are very simplified or even not considered, the general aim of this paper was to create, solve, and validate a numerical model of the coupled stress and thermal phenomena that occur within an SMES magnet. A finite element model has been developed to solve the coupling of the magnetic field, stress, and thermal problems. Temperature and stress distribution of the SMES magnet in two operating conditions are simulated, taking into account the eddy current, ac loss, and heat conduction. This provides useful insight for optimized coil design and condition assessment of SMES.

The Effect of Flux Diverters on Energy Storage Capacity and Heat Losses in a HTS SMES

Energy storage capacity and the heat losses are key factors in superconducting magnetic energy storage (SMES). In this paper, the use of flux diverters to increase the energy storage capacity and reduce the heat losses is analyzed in a HTS SMES magnet. The analysis is carried out using a 100 kJ SMES model based on FEM. The location, the geometry shape and the material configuration of flux diverters are investigated. To get an accurate loss reduction, magnetic losses of flux diverters are considered in heat loss calculation. The results show flux diverters are effective in the rated condition. Because the flux distribution is affected by the saturation level of flux diverters, the effect is related to the operating current.

Electromagnetic and Thermal Design of a Conduction-Cooling 150 kJ/100 kW Hybrid SMES System

Owing to the application of high-temperature superconductor (HTS) tapes, superconducting magnetic energy storage (SMES) magnets can be economical to run at temperatures around 20 K. The conduction-cooled SMES magnet has become a reality with the rapid development of cryocooler technology. In China, a 150 kJ/100 kW conduction-cooled SMES employed for power quality is now being developed by Huazhong University of Science and Technology (HUST) and Hubei Electric Power Company (HBEPC). In electromagnetic design, a hybrid structure that uses two kinds of HTS tapes is employed to increase the critical current, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> , of the SMES magnet. This paper presents an electromagnetic and thermal design of the conduction-cooling system for the magnet. The relationship between <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and temperature is analyzed, and the target parameters of the conduction cooling system are finalized. The design scheme of the cooling system is developed by analyzing thermal conductivity characteristics of HTS double-pancakes, thermal loads, thermal resistance, and cooling demands. Finite element analysis results show that the design scheme meets the requirements well in static conditions.

Distribution of AC loss in a HTS magnet for SMES with different operating conditions

The AC loss induced in superconducting tape may affect the performance of a superconducting device applied to power system, such as transformer, cable, motor and even Superconducting Magnetic Energy Storage (SMES). The operating condition of SMES is changeable due to the need of compensation to the active or reactive power according to the demand of a power grid. In this paper, it is investigated that the distribution of AC loss for a storage magnet on different operating conditions, which is based on finite element method (FEM) and measured properties of BSCCO/Ag tapes. This analytical method can be used to optimize the SMES magnet.

Stress Analysis for Toroid-Type HTS SMES Coil and Bobbin Structure Considering Large Parallel Magnetic Field

A 2.5 MJ HTS superconducting magnetic energy storage (SMES) system is under development to compensate the sag or instantaneous black out for a utility side. The toroidal-type structure is adapted to reduce the perpendicular magnetic field and the stray field at outside of SMES. A toroidal-type magnet shows a small perpendicular magnetic field. However, parallel magnetic field is much larger than perpendicular one. Therefore, Lorentz force of HTS tape can be so strong and the stress analysis should be carried out to verify that the maximum hoop stress and normal stress are in appropriate range. In addition, overall inward force of an HTS pancake winding in toroidal-type magnet is very strong and stress analysis for the bobbin and its supporting parts is important for a design a mechanically stable structure. This paper describes an analysis and design result for a toroidal -type HTS SMES magnet considering orthotropic material properties, large magnetic field and the resulting Lorentz force.

Mechanical Behavior Analysis of a 1 MJ SMES Magnet

For several decades, researches and developments on superconducting magnetic energy storage (SMES) system have been carried out actively world wide for efficient electric power management. A large bore NbTi superconducting magnet with liquid helium bath cooling has been developed in the Institute of Electrical Engineering, Chinese Academy of Sciences (IEE, CAS), which can be demonstrated as a micro-sized 1 MJ SMES. Even though the superconducting magnet is designed optimally in respect to the preload and electromagnetic force, consideration of mechanical integrity due to stress must not be neglected for the stable operation of the SMES system. Therefore, in order to study the mechanical behavior of the SMES magnet, a two-dimensional axisymmetric finite element analysis was performed. In the paper, the details of the magnet design, FEA model and results of the mechanical behavior analysis are presented.