Superconducting Magnetic Energy Storage System Research Articles

HTS magnet for 7.3 kJ SMES system

One of the most promising power applications of high - Tc superconductors are Superconducting Magnetic Energy Storage (SMES) systems for storing and instantaneous discharging large quantities of power. The SMES system stores energy in the magnetic field generated by the flow of DC current in a coil of superconducting material that has been cryogenically cooled. This paper describes design of a 7.3 kJ conduction - cooled, high - Tc superconducting (HTS) magnet for experimental SMES system. This magnet consists of 14 single pancake - coils wound with Bi-2223 High Strength Wire with critical current of 115 A at 77 K. The operating current of the magnet is 135 A at 35 K. The described magnet is cooled in high vacuum cryostat using two-stage G-M cryocooler SRDK-408.

Test Results of Power System Control by Experimental SMES

The authors have developed a solenoid model coil used for superconducting magnetic energy storage (SMES) for power system control, aimed at drastically reducing the costs of the SMES system. The single solenoid model coil of 2.9 MJ is designed with the rated current of 9.6 kA, a maximum magnetic field of 5.5 T and coil charge rates equivalent to those of the practical 100 MW/54 MJ class SMES. The coil is characterized by the use of an aluminum stabilized NbTi CIC (Cable-in-conduit) conductor. The experimental SMES consists mainly of a 2.9 MJ coil, the cooling system for the CIC conductor and the 1 MW class AC/DC converter. The SMES is connected to 6 kV distribution lines at a substation. In the field test, the SMES's 17 ms responses for the step input of active and reactive power were ascertained. Furthermore, its function of compensating for load fluctuation in the 6 kV distribution line was confirmed. The test results show the realization of a practical SMES system for power line control

Flexible Power Interconnection With SMES

Electric power networks are usually interconnected with each other through a back-to-back direct-current (DC) link to increase reliability of electric power networks and to improve system operations. The objective of this work is to discuss the concept of a superconducting magnetic energy storage (SMES) incorporated into a back-to-back interconnection. In this case, the back-to-back system is used as a power conditioning system for the SMES coils. Since the AC/DC converter can be designed independently of the frequency of the power system, a two-way switch is connected to the AC side of each converter. This two-way switch can select the interconnected power system. By using the two-way switches, this system can increase the availability factor of the back-to-back interconnection during the SMES operations and also enables the flexible power interchange between interconnected power networks with an optimal time interval for the power demand of each interconnected power network. This work discusses the design considerations of the back-to-back interconnection with the SMES that enables the replacement of a pumped hydro storage. In this case, the SMES system is composed of a number of superconducting coils in order to decrease the risk of the superconducting coil constructions by the effect of mass production. In this work, the SMES coils are optimized from the required mass of the structure and the leakage magnetic field

Design Considerations for SMES Systems Using<tex>$rm MgB_2$</tex>and/or High-Temperature Superconductors

MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and high-temperature superconductors (HTS) are expected to reduce refrigeration energy requirements for superconducting coils. If MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and HTS carry usable current densities at high magnetic fields, in contrast to NbTi superconductors, superconducting magnetic energy storage (SMES) systems will be realized in smaller coil dimensions and shorter conductor lengths. In this work, the design considerations for the SMES systems using MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and/or HTS coils have been discussed. The required specifications of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and HTS coils with a liquid hydrogen cooling are: (1) the target critical current density of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and HTS should be higher than 1000 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (w/o stabilizer) at 15~20 K and 5~10 T in order to improve small-sized SMES coils, (2) MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and HTS coils require about 50-kA class superconductors with lengths of 5~10 km from the viewpoint of the coil construction, (3) the coil windings should be optimized in order to prevent a decrease in the operating current density within an allowable stress of MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and HTS at high magnetic fields, (4) the force-balanced coil (FBC) is an optimal coil configuration that can enhance the operating current density and obtain the stored energy for the same current density about 100 times larger than that in the solenoid case by the effect of the minimization of the working stresses

Detailed Modeling of Superconducting Magnetic Energy Storage (SMES) System

This paper presents a detailed model for simulation of a Superconducting Magnetic Energy Storage (SMES) system. SMES technology has the potential to bring real power storage characteristic to the utility transmission and distribution systems. The principle of SMES system operation is reviewed in this paper. To understand transient and dynamic performance of a SMES system, a detailed SMES system benchmark model is given with extensive simulation results. This system is demonstrated using an electromagnetic transient program-PSCAD/EMTDC.

Development of a 3 MJ/750 kVA SMES system

Research and development on superconducting magnetic energy storage (SMES) system have been carried out to realize efficient electric power management for several decades. Korea Electrotechnology Research Institute (KERI) has developed a 3 MJ/750 kVA SMES system to improve power quality in sensitive electric loads. It consists of an IGBT based power converter, NbTi mixed matrix Rutherford cable superconducting magnet and a cryostat with HTS current leads. A computer code was developed to find the parameters of the SMES magnet which used minimum amount of superconductors for the same energy storage capability, and the 3 MJ SMES magnet was designed based upon that. This paper describes the fabrication and experimental results of the 3 MJ/750 kVA SMES system.

超電導磁気エネルギー貯蔵付き系統間連系設備

The objective of this work is to discuss the concept of back-to-back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back-to-back DC link. In this case, each converter of the back-to-back system is used as a power conditioning system for the SMES coils. Since the AC–DC converter can be designed independently of the frequency of the power system, a two-way switch is connected to the AC side of each converter. This two-way switch can select the interconnected power systems. By using the two-way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC–DC converters. For instance, lower-cost power of each power network can be stored through two converters during the off-peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back-to-back interconnection with SMES and discuses the optimal SMES configuration for a 300-MW-class back-to-back interconnection. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 37–43, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20482

Design and Preliminary Results of a Prototype HTS SMES Device

The University of Wollongong (UOW) has developed the design for a 20 kJ high transition temperature Superconducting Magnetic Energy Storage (SMES) device, and constructed a nominally 2.5 kJ prototype. The coil for the prototype was wound using High Temperature Superconducting (HTS) BSCCO-2223 tape. It was refrigerated to 20 K using a gaseous helium cold head cryocooler. The SMES device has been constructed as a prototype for a larger commercially realizable system, and hence is capable of supplying a 3-phase load during voltage sags or short (<1 s) power interruptions. This paper discusses the modeling and design of the electromagnetic and thermal aspects of the coil, the Power Control Circuit (PCC), current leads and cryogenic system. Also presented are preliminary results of the SMES coil, cryogenics, and system energy storage and delivery capabilities.

Advanced configuration of superconducting magnetic energy storage

\\Superconducting Magnetic Energy Storage (SMES) is very promising as a power storage system for load leveling or a power stabilizer. However, the strong electromagnetic force caused by high magnetic field and large current is a serious problem in SMES systems. To cope with this problem, we proposed the concept of Force-Balanced Coil (FBC), which is a helically wound toroidal coil. The FBC can minimize working stresses by selecting an optimal number of poloidal turns. However, the winding of the FBC has a complex three-dimensional shape that can make the manufacturing of the helical windings difficult. To overcome this difficulty, a helical winding machine was developed. From winding tests, the possibility of the coil construction was demonstrated. Moreover, a small helical coil using high temperature superconductors was designed and fabricated in order to estimate the problems of helical winding technique through the experimental results with liquid nitrogen cooling. This paper describes the design condition of the Force-Balanced Coil in order to reduce structure requirements and proposes a solution to the problems of helical winding technique by using experimental devices.

Scaling Law of Fringe Fields as Functions of Stored Energy and Maximum Magnetic Field for SMES Configurations

Although a SMES (superconducting magnetic energy storage system) has attractive potential for power management and quality control, the fringe field from the SMES restricts its site location. The fringe field outside a coil is expanded in a series of Legendre polynomials. The results are applied to the fringe fields of various SMES configurations, such as a single solenoid coil, toroidal coil, axially displaced coil. The derived fringe fields are scaled as functions of both the stored energy E and the maximum magnetic field B/sub m/, which are the main parameters of superconducting coil design. The fringe fields decrease as E/B/sub m/, (E/sup (n+2)//B/sub m//sup (2 n+1)/)/sup 1/3/, and ( E/sup 5//B/sub m//sup 7/)/sup 1/3/, for a single solenoid, toroidal coil, and axially-displaced coil configurations, respectively, where n is the number of coils.

Development and Performance Results of 5 MVA SMES for Bridging Instantaneous Voltage Dips

The superconducting magnetic energy storage system (SMES) of output 5 MVA has been developed to bridge instantaneous voltage dips. The field examination is executed by setting up this system at the new and large liquid crystal factory in Japan. The developed SMES system can store up to 7.34 MJ of magnetic energy in superconducting coils using the NbTi Rutherford conductor. The maximum output of the developed SMES is 5 MVA, and the system can discharge the output for one s. The operating current of the coil is 2.7 kA, and the rated voltage is 2.5 kV. The field examination was started in July 2003. During the field test, we will confirm the performance of bridging instantaneous voltage dips by SMES, the long-term drive reliability and the standby loss characteristic.

Fabrication and Test of a 3MJ SMES Magnet

For quite a long time many research and developments of superconducting magnetic energy storage (SMES) system have been doing for the enhancement of power quality control of a sensitive electric load. Korea Electrotechnology Research Institute (KERI) has developed a 3MJ, 750 kVA SMES system to improve power quality in sensitive electric loads. This paper describes the design, fabrication and experimental results for the 3MJ SMES magnet made by using the design code of a SMES device that we developed. A computer code was developed to find the parameters of the SMES magnet, which has a minimum amount of superconductor for the same stored energy. And the 3MJ SMES magnet was designed based upon those. In addition, the 3MJ SMES magnet that was ramp up to 1kA without quench.

Distribution of stress in force-balanced coils on virial theorem

Distributions of stress on a device with helical coils for the superconducting magnetic energy storage (SMES) are analyzed experimentally and numerically. In the previous work, we showed a theoretical limit of stored energy in a toroidal SMES system by the virial theorem. To verify the theoretical limit, we designed and construct a small device which is composed of two sets of helical superconducting coils and a toroidal frame of aluminum alloy. Strains by electromagnetic force on the frame were obtained experimentally. Distributions of stress on a toroidal shell with a similar configuration to the device are numerically calculated. Comparing the results of the experiments and the numerical calculations, a qualitative agreement of stress distribution between the calculation and the experiment is obtained in the toroidal direction, while discrepancies of stress in the poloidal direction are not negligible.

Statcom- SMES

This article presents the modeling and control of the integration of a StatCom (static-synchronous compensator) with SMES (superconducting magnetic energy storage system) and its dynamic response to system oscillations caused by a three-phase fault. It has been shown that the StatCom-SMES combination can be very effective in damping power system oscillations. Adding energy storage enhances the performance of a StatCom and possibly reduces the MVA ratings requirements of the StatCom operating alone. This is important for a cost/benefit analysis of installing flexible AC transmission system controllers on utility systems. It should be noted that, in this study, the StatCom provides a real power flow path for SMES, but the SMES controller is independent of the StatCom controller. While the StatCom is ordered to absorb or inject reactive power, the SMES is ordered to absorb/inject real power. It was also observed that the location where the combined compensator is connected is important for improvement of overall system dynamic performance. Although the use of a reactive power controller seems more effective in a load area, this simulation study shows that a StatCom with real power capability can damp the power system oscillations more effectively, thereby stabilizing the system faster-if the StatCom-SMES controller is located near a generation area rather than a load area.

Present state and future on electric power staorage. 4. Could superconducting magnetic energy storage system (SMES) be realized?

Present state and future on electric power staorage. 4. Could superconducting magnetic energy storage system (SMES) be realized?

Enhancement of transient stability of an industrial cogeneration system with superconducting magnetic energy storage unit

This paper has developed the coordination of load shedding scheme and superconducting magnetic energy storage (SMES) unit to enhance the transient stability of a large industry cogeneration facility. The load-shedding scheme and the tie line tripping strategy by using the frequency relays have been designed to prevent the power system from collapse when an external fault of utility power system occurs. An actual external fault case and a simulated internal fault case have been selected to verify the accuracy of the load shedding scheme by executing the transient stability analysis. To improve the frequency and voltage responses, an SMES unit with various control modes has been installed in the cogeneration system. The sensitivity analysis of the SMES unit with different parameters is applied to achieve better system responses. Besides, an SMES unit with active power deviation as feedback signal is also considered to improve the electric power fluctuation of the study plant with rolling mills. It is found that the SMES system will enhance the electric power quality and minimize the economic losses of the cogeneration facility due to unnecessary load shedding.

Enhancement of Transient Stability of an Industrial Cogeneration System with Superconducting Magnetic Energy Storage Unit

This paper has developed the coordination of load shedding scheme and superconducting magnetic energy storage (SMES) unit to enhance the transient stability of a large industry cogeneration facility. The load-shedding scheme and the tie-line tripping strategy by using the frequency relays have been designed to prevent the power system from collapse when an extemal fault of utility power system occurs. An actual extemal fault case and a simulated intemal fault case have been selected to verify the accuracy of the load shedding scheme by executing the transient stability analysis. To improve the frequency and voltage responses, an SMES unit with various control modes has been installed in the cogeneration system. The sensitivity analysis of the SMES unit with different parameters is applied to achieve better system responses. Besides, a SMES unit with active power deviation as feedback signal is also considered to improve the electric power fluctuation of the study plant with rolling mills. It is found that the SMES system will enhance the electric power quality and minimize the economic losses of the cogeneration facility due to unnecessary load shedding.

Design and test of a 1-MJ SMES system

For several decades researches and developments on superconducting magnetic energy storage (SMES) system have been done for efficient electric power management. Korea Electrotechnology Research Institute (KERI) have developed a 1-MJ 300-kVA SMES System for improving power quality in sensitive electric loads. It consists of an IGBT (Insulated Gate Bipolar Transistor) based power conversion module, NbTi mixed matrix conductor superconducting magnet and a cryostat with HTS current leads. The authors developed the code for design of a SMES magnet, which could find the parameters of the SMES magnet having minimum amount of superconductors for the same stored energy, and designed the 1-MJ SMES magnet by using it. And they have designed and fabricated cryostat with kA class HTS current leads for a 1-MJ SMES System. This paper describes the design, fabrication and experimental results for a 1-MJ SMES System.

ＳＭＥＳコイル配置の漏洩磁界に関する蓄積エネルギーと最大磁界の比例則

The recent developments of superconducting magnet technology allow us to construct a small and medium-scale SMES (Superconducting Magnetic Energy Storage System), which would be effectively used for electric power management and quality control because of its high convergence efficiency and its simultaneously quick response of real and reactive power. Since a SMES of this kind should be situated in a power substation or near a demand site, a stray field from superconducting coils restricts its use. The stray field outside a solenoid is analyzed by a series of Legendre polynomials; therefore the results are applied to various coil configurations. We derived the stray fields from various SMES configurations as a function of Rp, where Rp is distance from the coil. In this paper we analyzed the stray fields from single solenoid coil and toroidal coil arrangements, as functions of stored energy E and maximum magnetic field Bm, which are the main parameters of superconducting coil. The stray field from the single solenoid coil configuration decreases as E/Bm, and that from the toroidal coil configuration decreases as (E(n+2)/Bm(2n+1))1/3, where n is the number of coils.

ＳＭＥＳのコスト低減に向けての研究 ＳＭＥＳコスト低減設計 アルミ安定化ＮｂＴｉ ＣＩＣ／ソレノイドユニット結合型トロイダル方式

Superconducting magnetic energy storage (SMES) is a promising technology for electric utility stabilization of transmission, load compensation, and frequency regulation. This paper presents the results of a study to reduce the capital cost of an SMES system. The study focused on a toroidal-shaped superconducting coil system and concerned both 100MW/15kWh SMES for stabilization on transmission and 100MW/500kWh SMES for load compensation and frequency regulation. The charge/discharge ratio (k) was optimized in consideration of the economical efficiency of the whole SMES system, and thereby k=0.52 for small-scale SMES and k=0.86 for medium-scale SMES were obtained. To reduce the cost of a superconducting coil system, the system's design should be based on the concepts of a compact, a simple structure and small material amount. The aspect ratio of a toroidal coil system and that of a solenoid unit coil are determined from the viewpoints of minimum material amount. Aluminum-stabilized forced-flow superconductors have been newly proposed to achieve high voltage and high magnetic-field design in correspondence with small coils and reduced coil-turn numbers. New oxidization techniques for the aluminum surface of the stabilizer have been developed and the structure of the superconductor is designed simply and symmetrically to reduce manufacturing cost and ac loss. The supercondutor's favorable performances have been confirmed through short sample tests. These results provide a strong incentive for utilities to encourage and support the development of SMES cost-reduction technology.