HTS Superconducting Magnetic Energy Storage Research Articles

Electromagnetic Analysis on 2.5MJ High Temperature Superconducting Magnetic Energy Storage (SMES) Coil to be used in Uninterruptible Power Applications

Abstract In recent years, due to the digitization of the electrical devices electric load demand has been increased. Power security and stabilization are the other two challenges which necessitate the need of electrical energy storage. Along with the technological constraints, economical and environmental issues are the other challenges in the development of energy storage technologies. Fast response and high energy density features are the two key points due to which Superconducting Magnetic Energy Storage (SMES) Devices can work efficiently while stabilizing the power grid. Two types of geometrical combinations have been utilized in the expansion of SMES devices till today; solenoidal and toroidal. It has been found that the solenoidal arrangement is easier to fabricate and provides efficient approach to handle stresses produced by Lorentz forces. This work represents the development of 2.5MJ SMES solenoidal Magnet using 2G (SuperPower, YBCO having Tc=90K @ 0T) HTS tape. The effect of the operating current (passing through a single superconducting tape) has been evaluated. A reference magnetic flux of 3.5T has been considered in designing of HTS SMES. It has been found that the parallel fields for solenoidal magnet are large as compared to perpendicular fields which results into large magnitudes of Lorentz forces acting on HTS tape which may leading to structural instabilities and can cause failure. It has been concluded that higher currents can be used in order to lower down the total length of the superconductor as it can reduce the overall cost of the device

AC Loss Analysis of a Single-Solenoid HTS SMES Based on H-formulation

There will be much AC loss generated when a superconducting magnetic energy storage(SMES) is applied in a power system to exchange power with a power network or other equipment. AC loss may cause the instability and risk of burnout to SMES. This paper presents a commonly used SMES design scheme and lists the design parameters of a 10MJ/5MW SMES. We used the finite element software COMSOL to build a simulation model to calculate the AC loss during its operation. We get the calculated results and analyse AC loss`s distribution characteristics of the 10MJ/5MW SMES which uses a single screw structure.

Cost Estimation Models of MJ Class HTS Superconducting Magnetic Energy Storage Magnets

An HTS superconducting magnetic energy storage (SMES) can be utilized to improve the security and stability of the power grid with renewable energy generation. In different application scenarios, the requirements for capacity and power of the SMES varies, which needs the appropriate SMES allocation in the power grid. A cost estimation is the key component for the SMES allocation. Therefore, this paper proposed a cost estimation method of an HTS SMES, which synthetically considers the design, manufacture, operation, maintenance, and application scenarios. First, the cost estimation model of an HTS SMES was proposed based on the optimal superconducting magnet design. Then, adopting typical scenarios in the power grid, the economic capacity of SMES allocations were analyzed. Finally, the cost trend of an HTS SMES was carried out based on the development trend of assembly units.

New Structure Design of Magnet for 1 MJ HTS SMES

In recent years, the superconducting technology is popular in our production and life. An increasing number of researchers and institutions participate in study of the super-conducting magnetic energy storage (SMES) system. SMES is widely used in power sup-ply system, new energy system and pulsed power supply system. However, the leakage magnetic field of traditional SMES is more serious, which limited the application in engi-neering. This paper proposes an improved scheme for the 1 MJ single-solenoid structure magnet by using the actively shielding theory. Moreover, by using particle swarm optimi-zation, the structural parameters of the superconducting magnets are optimized respec-tively. Finally, the ANSYS modeling simulation is built by these structural parameters, all simulation data are analyzed and compared.

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.

Performance Analysis of a Toroid-Type HTS SMES Adopted for Frequency Stabilization

Superconducting magnetic energy storage (SMES) can overcome fluctuations in frequency because of its fast response time in charging and discharging energy. To stabilize the fluctuations in frequency of wind power generation systems (WPGSs), HTS SMES systems should be connected to the terminal of the WPGSs. Ulleung Island's power network in Korea was modeled with a real-time digital simulator (RTDS) to demonstrate the effectiveness of SMES at stabilizing frequency. A toroid-type HTS SMES cooled by conduction cooling and a DC/DC chopper to charge and discharge current were fabricated for the experiment. The simulation results show the frequency stabilization effected by the HTS SMES system with its operational characteristics such as real time variation in current and temperature.

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.

Structural design of the toroidal configuration of the HTS SMES cooling system

The superconducting magnetic energy storage (SMES) system is working on around 30K, because the magnet is made of high temperature superconductor. To maintain the cryogenic temperature, the superconducting coil is cooled by cryogen, helium gas or liquid neon. But there are some weak points in the cryogen cooling system. For example periodic charge of the cryogen and size is big and so on. So, we have designed the conduction cooling system for toroidal configuration HTS SMES. The toroidal type HTS SMES has some merits, so it is very small magnetic field leakage, and magnetic field applied perpendicular to the tape surface can be reduced. Our system has 28 numbers of HTS double pancake coils and they are arrayed toroidal configuration. The toroidal inner radius is 162mm, and outer radius is 599mm, and height is about 162mm.In this study, we have designed the cooling structure and analyzed temperature distribution of cooling path, thermal stress and deformation of the cooling structure.

Quench simulation of SMES consisting of some superconducting coils

In recent years, many HTS superconducting magnetic energy storage (HTS-SMES) systems are investigated and designed. They usually consist of some superconducting element coils due to storing excessively high energy. If one of them was quenched, the storage energy of the superconducting element coil quenched has to be immediately dispersed to protect the HTS-SMES system. As the result, the current of the other element coils, which do not reach to quench, increases since the magnetic coupling between the quenched element coil and the others are excessively strong. The increase of the current may cause the quench of the other element coils. If the energy dispersion of the element coil quenched was failed, the other superconducting element coil would be quenched in series. Therefore, it is necessary to investigate the behavior of the HTS-SMES after quenching one or more element coils. To protect a chain of quenches, it is also important to investigate the time constant of the coils. We have developed a simulation code to investigate the behavior of the HTS-SMES. By the quench simulation, it is indicated that a chain of quenches is caused by a quench of one element coil.

A novel HTS SMES application in combination with a permanent magnet synchronous generator type wind power generation system

Superconducting magnetic energy storage (SMES) system is a DC current driven device and can be utilized to improve power quality particularly in connection with renewable energy sources due to higher efficiency and faster response than other devices. This paper suggests a novel connection topology of SMES which can smoothen the output power flow of the wind power generation system (WPGS). The structure of the proposed system is cost-effective because it reduces a power converter in comparison with a conventional application of SMES. One more advantage of SMES in the proposed system is to improve the capability of low voltage ride through (LVRT) for the permanent magnet synchronous generator (PMSG) type WPGS. The proposed system including a SMES has been modeled and analyzed by a PSCAD/EMTDC. The simulation results show the effectiveness of the novel SMES application strategy to not only mitigate the output power of the PMSG but also improve the capability of LVRT for PMSG type WPGS.

A feasibility study on HTS SMES applications for power quality enhancement through both software simulations and hardware-based experiments

Superconducting magnetic energy storage (SMES) which promises the efficiency of more than 95% and fast response becomes a competitive energy storage device. Because of its advantages, SMES can provide benefit as a power quality enhancement device to an utility especially in connection with renewable energy sources. In this paper, a software simulation and an experiment aiming for power quality enhancement are reported. The utility was referred to Ulleung Island in Korea which had one wind power generation system. The simulation was performed using power system computer aided design/electromagnetic transient including DC (PSCAD/EMTDC) and power-hardware-in-the-loop simulation (PHILS) was implemented to monitor the operational characteristics of SMES when it was connected to utility. This study provides a highly reliable simulation results, and the feasibility of a SMES application is discussed.

HTS SMES Application for the Frequency Stabilization of Grid-Connected Wind Power Generation System

Output power of the wind power generation system (WPGS) fluctuates due to wind speed variation and affects the frequency and voltage fluctuations of the utility. Superconducting Magnetic Energy Storage (SMES) can overcome these fluctuations because of fast response time for energy charging and discharging. To stabilize the frequency fluctuation, HTS SMES should be connected to the terminal of the WPGS. Ulleung island power network in Korea was modeled to demonstrate the effectiveness of SMES for frequency stabilization. Based on the simulation results using EMTDC, a toroidal-type HTS SMES cooled by conduction cooling method and a DC/DC chopper for current charging and discharging were fabricated for experiment. Power network including WPGS was implemented through a Real Time Digital Simulator (RTDS). The simulation and experimental results for frequency stabilization using real HTS SMES and RTDS are discussed in detail.

Design and Manufacturing of a SMES Model Coil for Real Time Digital Simulator Based Power Quality Enhancement Simulation

The Superconducting Magnetic Energy Storage (SMES) system is a key technology for overcoming the voltage sag, swell, interruption, and frequency fluctuation with the fast response speed of current charge and discharge. A toroidal-type SMES is designed using a 3D CAD program, and the inductance and AC loss characteristic during operation are analysed using Finite Element Method (FEM) program. The toroidal-type magnet consists of 30 double pancake coils (DPC). The single pancake coils (SPC), constituting the double pancake coils, are arranged at an angle of 6° from each other, based on the central axis of the toroidal-type magnet. The conduction cooling method is used for the toroidal-type SMES cooling. To evaluate the characteristics of the over-mega-joule class grid-connected HTS SMES system, the authors implemented a simulation by which the SMES coil could be connected to the Real Time Digital Simulator (RTDS). Using the simulation, users can perform voltage sag and frequency stabilization simulations with a real SMES coil in real time and easily change the capacity of the SMES system as much as they need. The effectiveness of the toroidal-type HTS SMES system is demonstrated through the RTDS-based simulation and the results are briefly discussed.

A Study on Basic Insulation Characteristics of 2.5 MJ Class Conduction-Cooled HTS SMES

Superconducting magnetic energy storage (SMES) is a cutting-edge electric power storage system which transforms electric energy to magnetic energy for storage, and again to electric energy for use. Especially, 1~3 MJ class SMES for power compensation does not cost much initial production expenses, and can be used as alternative electric power upon emergency situations such as power failure. Moreover, toroidal coil is used instead of solenoid coil to reduce the effect of magnetic field on environment. In general, toroidal coil is cooled down by cryogen, but in this study, adopted was the conduction cooling method, which cools down the coil by the cryocooler. For this method, electric insulation to protect the cryocooler from current lead is very important. Thus, this study clarified the insulation elements of 2.5 MJ class conduction-cooled high temperature superconducting SMES, and investigated the basic insulation characteristics of each element.

An Experimental Study of the Conduction Cooling System for the 600 kJ HTS SMES

The characteristic of the superconducting magnetic energy storage (SMES) system is more fast response, long life time, more economical, and environment-friendly than other uninterruptible power supply (UPS) using the battery. So, the SMES system can be used to develop methods for improving power quality where a short interruption of power could lead to a long and costly shutdown. Recently, cryogen free SMES is developed briskly based on BSCCO wire. We fabricated and tested the conduction cooling system for the 600 kJ class HTS SMES. The experiment was accomplished for simulation coils. The simulation coils were made of aluminum, and have inner and outer coil diameters of 460 mm and 728 mm and coil height of 237 mm. The mass of coil is 171.6 kg, it is equivalent to thermal mass of 600 kJ HTS SMES coil. The coil is cooled with two GM coolers through the copper conduction bar. In this paper, we report the test results of cool-down and heat loads characteristics of the simulation coils.

Temperature Distribution of Cryogenic Conduction Cooling System for a HTS SMES

HTS superconducting magnetic energy storage (SMES) systems need cryogenic cooling systems. Conduction cooling system has more effective, compact structure than cryogen. In general, two stage GM cryocoolers are used for conduction cooling of HTS SMES system. First stages of cryocoolers are used for the cooling of current leads and radiation shields, and second stages of cryocoolers for HTS coil. The cryocooler has a limited cooling capacity. So radiation shields are used to minimize the heat leak to the HTS coil. For the effective conduction cooling of the HTS SMES system, the temperature difference between the cryocooler and HTS coil should be minimized. In this paper, a cryogenic conduction cooling system for HTS SMES is analyzed to evaluate the performance of the conduction cooling system. The heat transfer analysis is carried out in steady state with the heat generation of the HTS coil and effects of the thermal contact resistance. The results show the effects of the heat generation and thermal contact resistance on the temperature distribution.

Current status of SMES in Korea

The first superconducting magnetic energy storage (SMES) in Korea was fabricated in 1987. During 15 years after this, several SMES projects were carried out and many improvements were made. Presently, two main SMES projects are undergoing in Korea. One is low T c SMES commercialization project and the other is HTS SMES design project. This paper describes a brief history of SMES development and the two main undergoing SMES projects in Korea.

HTS SMES magnet design and test results

This paper describes design, construction, and testing of a 5 kJ superconducting magnetic energy storage (SMES) magnet. This magnet was built by American Superconductor Corporation (ASC) for Gesellschaft fur Innovative Energieumwandlung und Speicherung (EUS) of Germany. The magnet consists of a solenoidal coil constructed from a silver-sheathed BiPb/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 2/O (Bi-2223) conductor which was reacted before winding. The coil is epoxy impregnated and cooled with single stage Gifford McMahon (G-M) cryocoolers for operation at 100 A (DC) with substantial AC components due to the frequent variation of current (ramp-up and ramp-down.) The magnet was tested in early spring of 1996 and was shipped to EUS in mid June. The successful operation of this magnet illustrates that the technology of cooling HTS magnets with G-M type cryocooler is now fully established. The long-term operation of this magnet at EUS will verify the reliability of HTS magnet system in critical applications and will open future applications for HTS in the area of SMES and other magnets.