SMES System Research Articles

A 100 MJ SMES demonstration at FSU-caps

The Center for Advanced Power Systems (CAPS) at Florida State University (FSU) was recently established to pursue research and education in power engineering. Development and demonstration of superconducting technologies is one of the cornerstones of the CAPS program. Important aspects of the program are the test of superconducting equipment at power levels up to 5 MW, and the creation of a reconfigurable network that will support pulsed power testing. A 100 MJ SMES system is being completed at BWX Technologies for integration to the CAPS test facility, to allow pulsed power operation of the testbed. The SMES coil, scheduled for completion in 2003, is based on cable-in-conduit technology and NbTi superconductor. The full system (including cryostat and power converter) will be integrated at CAPS and be operational in late 2004.

Safety and tolerability of high-dose quetiapine in treatment refactory schizophrenia: Preliminary results from an open-label trial

ASC multifilamentary composite tape based on BSCCO-2223 high temperature superconductor (HTS) and a scalable rolling process has reached a record superconductor critical current density Jc (77 K, 0 T) of up to 58,000 A/cm2, and engineering (full cross-section including metal sheath) Je (77 K, 0 T) up to 15,000 A/cm2. Pilot manufacturing of long lengths (100–400 m) has permitted a variety of increasingly significant prototypes, including a 200 hp ac synchronous motor, a 3300 A (77 K) 50 m machine-stranded cable conductor, a 5 kJ SMES system, and an operational ion-beam switching magnet installed in a tandem accelerator for carbon mass spectrometry dating. Recent ASC progress in manufacturing with Je over 8000 A/cm2 creates new opportunities for yet more advanced prototypes and commercial development.

Cryocooler cooled HTS current leads for a 1 MJ/1 MW-Class SMES system

Within the Italian project for the development of 1 MJ/1 MW SMES, Ansaldo-CRIS and CESI have been involved in the design and manufacturing of 1100 A resistive/HTS current leads conduction cooled by a closed cycle refrigerator. Main design and technological problems concern the achievement of electrical insulation between cryocooler and current leads at the voltage level of 6 kV together with a thermal contact good enough to keep the upper part of the HTS material at a temperature below 70 K, when the cryocooler temperature is 60 K and about 100 W is the thermal load. Thermal transport properties of electrical insulating materials as thin sheet placed between copper massive plates have been measured as a function of temperature and hence, according to the measured thermal performances, the area for thermal contact with the cryocooler has been suitably dimensioned. Mechanical structure for the whole current leads has been designed and manufactured. Final assembly of resistive section has been completed. Results about the achieved lead performances are presented and discussed.

Cryogenics of a conduction-cooled Nb/sub 3/Sn SMES

A cryogen-free Nb/sub 3/Sn SMES system operating at 10 K has been constructed in order to compensate a short term loss of power. The system is cooled with two Gifford-McMahon cryocoolers with a cooling power of 8 W at 10 K. SMES is an AC device and the cryogenic design is assigned by the application of the system and its specific AC requirements. Thus the minimization of both the coil AC losses and all the external losses becomes highly relevant. The former demand requires especially a careful design of a copper cryogenic interface between the coil and the cryocooler, the latter pretension implies a heat economical cryostat structure with HTS current leads. The cooling experiences of the system are discussed. In addition the cryogenic interface acts as a protection system of the magnet. The philosophy of this so called quench back effect is also outlined.

Design of a 200-kJ HTS SMES System

In this paper, optimization of an HTS SMES coil as a part of a 200-kJ HTS SMES system has been realized. A 1+1 evolution strategy with the line element method was used to optimize the shape of the coil. In order to ensure the desired energy storage capacity, final dimensions of the coil were recalculated with the finite element method (FEM).

ＳＭＥＳのコスト低減に向けての研究 ＳＭＥＳコスト低減技術開発と今後の見通し

Optimal SMES system concepts were developed for power system stabilization (available capacity of 54MJ, available output power of 100MW) and load fluctuation compensation or frequency regulation (available capacity of 1, 800MJ, available output power of 100MW) applications. The system details designs mainly composed of the superconducting coil, which aimed to achieve a cost decrease for each usage, based on four different schemes. The details of the designs and cost-reduction efforts were reviewed. Furthermore, to verify the validity of the development concept and the performance based on the detailed design result of the superconductor, five kinds of short superconductors (about 10m) selected respectively from among four kinds of superconductors were made for trial purposes. The performance of these prototypes was analyzed, including the measurement of current-carrying characteristics, stability and AC loss. Especially, the AC loss characteristic was measured with two devices: “superconductor coupling loss measurement device” of Kagoshima University; and “actual AC loss measurement device”, equipment was that built to enable the measurement and assessment of AC loss under conditions closely approximating the actual magnetic fields.

ＳＭＥＳのコスト低減に向けての研究 ＳＭＥＳコスト低減の必要性

ＳＭＥＳのコスト低減に向けての研究 ＳＭＥＳコスト低減の必要性

ＳＭＥＳのコスト低減に向けての研究 ＳＭＥＳコスト低減技術の提案 ＮｂＴｉ ＣＩＣ導体（安定化銅分離）／マルチポールソレノイド方式

A cost reduction study of 100MW/15kWh SMES for power system stabilization and 100MW/500kWh SMES for fluctuating load compensation and frequency control is performed. The optimization of SMES capacity factors and rated magnetic fields for each system shows that the optimum capacity factor of 100MW/15kWh SMES is lower than that of 100MW/500kWh SMES. And the optimum magnetic field at the point of minimum cost is about 3T, lower than that of usual NbTi magnets. A multipole solenoid system with NbTi CIC conductor is proposed as a cost-reduced SMES system. To reduce the number of superconducting strands, the copper stabilizer segregated from the strand, and a strand cross-section structure is simplified from the first-phase SMES project design for cost reduction. To reduce long-term AC loss, the strand has a CuNi sheath, and cables are twisted up to the second degree, which is much lower than that of the cable designed for the first-phase SMES coil.

ＳＭＥＳのコスト低減に向けての研究 Ｎｂ３Ｓｎ導体使用によるＳＭＥＳの低コスト化の可能性

A cost-reduction design of the SMES system is proposed, using Nb3Sn conductors that in recent years have shown progress in cost and performance. The main feature of this design should be a combination of Nb3Sn single-strand conductors and a small bore solenoid (=CELL) coil. The cost reduction was intended to use mass production methods and to operate small or medium-sized factories. However, this simple and compact design brings up new issues. Quench protection is especially a key issue. It needs high-speed quench detection and forced-quench that will reduce the unbalance magnetic force at quench and prevent the CELL coil from burning up. This cost-reduction design of the SMES system using Nb3Sn conductors is sufficiently competitive with the other designs that use NbTi conductors.

SMES system for study on utility and customer power applications

A grid model SMES system was developed for study on utility and customer power applications. The system consists of a 20 kJ NbTi magnet, a 15 kW 12-pulse IGBT current source converter and a DSP-based controller. To reduce the heat leakage, a couple of HTS current leads were designed and fabricated which are composed of Bi-2223 tapes and have a maximum operating current of 150 A. The 12-pulse current source topology was chosen for the converter not only owing to its low total harmonic distortion (THD) but also to its high capability of injecting capacitive reactive power into network. In the controller of the system two very fast DSPs (TMS320C32) are used to implement the control algorithms and perform the generation of the firing signals, giving a high accuracy and a high speed of response.

Studies on power conditioning system for SMES in ITER

The International Thermonuclear Experimental Reactor (ITER) draws huge power from utility power grid and it may cause some problems in the power system. Especially, the power required to control the movement of plasma caused by some instabilities of the plasma is suitable for compensation by SMES, because the time duration is a few seconds although the required power is around 100 MW. In this system, the design of the power conditioning system is one of the keys. As a power conditioning system, two systems were studied; one is the system using line commutation and light triggered thyristors, another is the system of multi-series converters using forced commutation and gate turn-off devices such as GTOs. Feature of the former circuit is the inter-phase DC reactor-less configuration. Thyristor rectifiers are directly connected in parallel at DC side, primary side windings of rectifier transformers are connected in series in order to ensure equal sharing of current between rectifiers. Reactive power can be compensated by TSC (thyristor switched capacitors). The performances of two proposed circuits were studied by computer simulation.

Protection of conduction cooled Nb/sub 3/Sn SMES coil

A conduction cooled Nb/sub 3/Sn SMES coil requires a protection analysis different from that of the liquid helium cooled NbTi magnets. In an SMES coil constructed with a bronze processed Nb/sub 3/Sn wire, hot spot temperature is high due to a slow normal zone propagation. In a conduction cooled system, the eddy current generated heating in the cryogenic interface enables a quench back. In order to design a proper protection scheme for a cryogen free Nb/sub 3/Sn SMES system operating at 10 K, a computer code has been developed. The code simulates the quench behaviour of the coil protected with any combination of a shunt resistor, subdivision and quench back. The modelling of the quench back requires the solution of the eddy current problem and the heat transfer between the coil and the interface. These are combined with the solution of the differential equations describing the protection with a shunt resistor or subdivision. Utilizing the developed code, the protection of a 0.2 MJ conduction cooled Nb/sub 3/Sn SMES coil has been designed.

SMES control algorithms for improving customer power quality

Control algorithms of SMES based on a 12-pulse IGBT current source converter were developed for improving customer power quality. The control performances include uninterruptible power supplies (UPS) and load fluctuation leveling. To demonstrate the control algorithms, both simulations and experiments were carried out on a 20 kJ/15 kW grid model SMES system. The results of the simulations and experiments are presented and compared in this paper.

Characteristics of NbTi mechanical persistent current switch and mechanism of superconducting connection at contact

A Persistent Current Switch (PCS) in a SMES system requires not only low ON resistance but also high OFF resistance in order to efficiently perform a load-leveling operation. Because a mechanical switch has the advantage of infinite OFF resistance, it can operate without generating Joule losses during the coil excitation and energy transfer process. However, it will cause an energy storage loss as long as the ON resistance, which mainly depends on contact resistance, is not decreased to zero. In this study, firstly case studies on energy losses due to the ON resistance of a mechanical switch and OFF resistance of a superconducting switch are carried out so as to show the necessity of a mechanical switch as a PCS in a large-scale SMES system. Secondly the contact resistance characteristics of a mechanical switch with NbTi bulk contact pieces are experimentally investigated as a function of switch driving force, switch pressing force, and ON–OFF operation number. Additionally, the effects of contact piece shape and its surface roughness on the contact resistance are examined. It was found that a superconducting connection at contact can be realized even if the switch is repeatedly opened and closed many times. The developed mechanical PCS, which has zero contact resistance, supports a superconducting current flow of more than 200 A. The formation mechanism of the superconducting connection at contact is modeled and analyzed based on theoretical considerations.

Development of a 400 kJ Nb3Sn superconducting magnet for an SMES system

An Nb3Sn superconducting magnet to store 400 kJ was developed as a unit magnet for a 2.4-MJ SMES system used for stabilization studies of electrical power systems. The superconducting magnet consists of a cryostat and an Nb3Sn coil. The dimensions of the coil are: 340 mm inner diameter, 700 mm outer diameter and 177 mm axial length. The pool-cooled coil is a stack of 20 Nb3Sn double pancakes, and the cooling channels are aligned between pancake coils. To reduce Joule loss in electrical power converters, the maximum operating current of the coil is designed to be 350 A, which is one order of magnitude less than the operating currents of similar scale coils for pulse use. The conductor is an Nb3Sn monolithic conductor with cross section 1.50 × 2.38 mm. For good superconducting stability and high dielectric strength of the coil, the Nb3Sn double pancakes were wound by the react-and-wind technique. Operation of dc current to 105% (367.5 A) of the design operating current was achieved without quench. After the whole of the coil was exposed out of liquid helium, the coil did not quench under 120 A current operation for more than 2 hours. It was verified that the coil was stable for the SMES system. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 44–52, 1997

Progress in BSCCO-2223 tape technology

ASC multifilamentary composite tape based on BSCCO-2223 high temperature superconductor (HTS) and a scalable rolling process has reached a record superconductor critical current density J c (77 K, 0 T) of up to 58,000 A/cm 2, and engineering (full cross-section including metal sheath) J e (77 K, 0 T) up to 15,000 A/cm 2. Pilot manufacturing of long lengths (100–400 m) has permitted a variety of increasingly significant prototypes, including a 200 hp ac synchronous motor, a 3300 A (77 K) 50 m machine-stranded cable conductor, a 5 kJ SMES system, and an operational ion-beam switching magnet installed in a tandem accelerator for carbon mass spectrometry dating. Recent ASC progress in manufacturing with Je over 8000 A/cm 2 creates new opportunities for yet more advanced prototypes and commercial development.

Development of HTS (high‐temperature‐superconductor) current leads for 1‐MW/1‐kWh modular SMES system

We are developing high-temperature-superconductor (HTS) current loads for a 1-MW/1-kWh modular SMES system. In the modular SMES system, a pair of current leads would be installed in each module so that the heat load to the low-temperature end through the leads is minimized. Design study of the lead configuration including the safety lead and its thermal characteristics is presented herein. The safety lead composed of stainless steel is placed in parallel to the bulk HTS. A test unit for verification of safe operation has been developed and the simulated bulk HTS quench test has been demonstrated. The maximum temperature of the safety lead reached 200 K and the terminal voltage of the safety lead was only 1.2 V in the case of a 1000-A quench test. This temperature rise was well below the designed value. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(1): 23–32, 1997

Development of HTS (high-temperature-superconductor) current leads for 1-MW/1-kWh modular SMES system

We are developing high-temperature-superconductor (HTS) current loads for a 1-MW/1-kWh modular SMES system. In the modular SMES system, a pair of current leads would be installed in each module so that the heat load to the low-temperature end through the leads is minimized. Design study of the lead configuration including the safety lead and its thermal characteristics is presented herein. The safety lead composed of stainless steel is placed in parallel to the bulk HTS. A test unit for verification of safe operation has been developed and the simulated bulk HTS quench test has been demonstrated. The maximum temperature of the safety lead reached 200 K and the terminal voltage of the safety lead was only 1.2 V in the case of a 1000-A quench test. This temperature rise was well below the designed value. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(1): 23–32, 1997

Experimental and simulated results of a SMES fed by a current source inverter

This paper presents the first experimental results obtained with a 6-pulse, 50 kW GTO current source inverter (CSI) feeding a 25 kJ superconducting coil. This SMES system is the first step into the project AMAS500 which consists of developing a 1 MJ SMES fed by a 500 kW CSI. The complete system will be in operation at the end of this year, but this paper shows the first results of the 25 kJ SMES when compensating a voltage oscillation in a scaled network. The paper is mainly focused on showing the experimental results of the 50 kW power converter and its comparison with simulation results obtained by means of EMTP and SABER/sup TM/ simulators. The very good agreement obtained between both results has validated the simulation models. Based on these models, the design of a 500 kW power converter has been carried out. The results of simulating the 12-pulse 500 kW CSI feeding a 1 MJ superconducting coil are also presented in this paper.

Superconducting magnetic energy storage for substation applications

Requirements and possible configurations for a SMES operating in 15 kV substations are discussed. The system will experience /spl sim/25 full discharges a year. Such a SMES system should provide 1 to 2 second-ride through capability, a response time of less than 8 milliseconds, and demonstrate a high efficiency.