SMES Coil Research Articles

Study on HTS SMES Coil for Optimized Dimensions

Study on HTS SMES Coil for Optimized Dimensions

HVDC Interconnections with SMES Device for PV and Wind Hybrid Power Transmission System

Abstract: The consumption of power shows a steeply increasing behavior in the present scenario which demands the integration of various novel techniques to the existing grid. With the penetration of PV and wind energy units into the grid, the evolution from a generator dominated grid to an inverter dominated grid arises in the near future. The paper discusses the characterization of HVDC convertors with the behavior of SG emulating virtual inertia for frequency stabilization and proper power oscillation damping during transmission of renewable energy based power. The conventional control of HVDC converters is integrated with synchronous power controller with second order characteristics inside power control loop for proper damping essentialities. The functioning of HVDC link is enhanced by means of SMES coil based energy storage operation. The proposed formulation is applied to a four area model in IEEE 14 bus system incorporated with PV, wind and HVDC links. The dynamic behavioral improvements are tested by means of MATLAB simulation.

50 kJ SMES magnet design optimization using real coded genetic algorithm

SMES systems are being made and utilized for various applications i.e. dampening low frequency oscillations, instantaneous voltage drop compensation, pulsating power supply etc. Due to tape like structure of 2G HTS and fabrication limits of long continuous length , SMES coil is made via assembling individual single pancake coil/double pancaked coil in the solenoid or toroid fashion. A SMES magnet is designed optimally, using real coded genetic algorithm, with minimum length as objective function for fxed amount of stored energy(50 kJ), using 2G HTS tape. Simulated binary crossover and polynomial mutation function are used for crossover and mutation respectively. Elitism is also used for faster convergence of genetic algorithm. An minimum length is found for 50 kJ stored energy. Stress calculation is carried out for this confguration.

Superconducting Properties of a Prototype Pancake Coil using a MgB2 Rutherford-type Stranded Conductor

Our group has developed a coil using MgB2 wires for SMES. In this paper, a prototype coil using a MgB2 Rutherford-type stranded conductor was fabricated based on react-and-wind (R&W) method. In the R&W method, a Rutherford-type conductor in which nine MgB2 wires were wound at pitch of 450 mm around a copper former were manufactured using reacted wires (performed by Columbus Superconductors SpA), and then coiling was performed. The coil was cooled by conduction cooling and the I-V properties were evaluated under magnetic field. As a result, in the R&W method, critical current of a coil was degraded, since making a coil by hand would cause the strain beyond the scope of the assumption which was the marginally allowable bending strain. This result suggests the coil for SMES proposed in ASPCS is difficult to react before twisting, and Rutherford-type conductors should be fabricated before reacting, which means that coil processing should be performed based on the React after making stranded conductors and Wind method, or the wind-and-react method.

An Optimization of Superconducting Coil Installed in an HVDC-Wind Farm for Alleviating Power Fluctuation and Limiting Fault Current

The vital problems of a high-voltage direct current (HVdc) wind farm are the dc power fluctuation and dc faults. To tackle both problems simultaneously, the superconducting magnetic energy storage with fault current limiting capability (SMES-FCL), which is incorporated into the HVdc-wind farm system, is proposed. The SMES-FCL can be used to lessen the dc power fluctuation due to intermittent wind power and limit the fault current in the dc line. The optimal SMES coil and control parameters are tuned based on minimization of power and voltage fluctuations, and stored energy. Study results elucidate that the optimal SMES-FCL provides higher effect on power smoothing and fault current limiting than the non-optimal SMES-FCL against dc fault and wind power levels.

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.

Characteristics of Compensation for Fluctuating Output Power of a Solar Power Generator in a Hybrid Energy Storage System Using a Bi2223 SMES Coil Cooled by Thermosiphon With Liquid Hydrogen

Due to global issue of energy shortage, alternative energy such as solar and wind energy has to be introduced to the commercial electricity grid. A hybrid energy storage system which is able to convert unstable alternative energy into constant electricity has been proposed. The hybrid energy storage system is composed of hydrogen system and SMES system. This research concerns on the issue of continuous operation of SMES system by introducing a threshold voltage range into the SMES control method. This control method was applied to an SMES coil in a 1-kW-class hybrid energy storage model system. Using the control method, we could restrain the temperature rise of the SMES coil. An experiment has been carried out to confirm the effectiveness of the control method in continuous operation of the hybrid energy storage system. The fluctuation output of a solar power generator was appropriately compensated by electrolyzer and SMES systems.

Design and Comparison of a 1-MW/5-s HTS SMES With Toroidal and Solenoidal Geometry

The design of a HTS SMES coil with solenoidal and toroidal geometry is carried out based on a commercially available 2G HTS conductor. A SMES system of practical interest (1 MW / 5 s) is considered. The comparison between ideal toroidal and solenoidal geometry is first discussed and the criteria used for choosing the geometrical parameters of the coils' bore are explained. The design of the real coil is then carried out and the final amount of conductor needed is compared. A preliminary comparison of the two coils in terms of AC loss during one charge discharge cycle is also discussed.

Design Study on Pulsed Power Supplies for the J-PARC Main Ring Magnets Using SMES

The proton synchrotron of J-PARC provides 30 GeV of a high-intensity proton beam. In a rapid-cycling operation scenario with 1 s of the cycling period, the peak-to-peak power disturbance will be 140 MW. In order to minimize the peak power from the grid, the authors discussed the feasibility of SMES for the 30-GeV rapid-cycling operation and carried out the design study on the power converter system and the SMES coils based on the simulation results and the magnetic field analysis. In this paper, the authors propose an optimal power converter topology with SMES, which is composed of thyristor converters, the main ring (MR) magnets, and SMES linked by the dc voltage source capacitor. The required power for the rapid-cycling operation is mainly transferred between the MR magnets and SMES. The thyristor converters for the grid connection provide a constant current to the dc link in order to compensate the power losses. Using the 20-MJ class SMES, the required power from the grid can be reduced to 3.4 MW of the constant power.

Jointless Pancake Coil Winding for Minimizing Electrical Loss in HTS SMES for Wind Power

Many different applications of superconducting devices have been designed using a modular pancake arrangement. It has been reported that this modular pancake structure provides excellent mechanical holding, effective cooling, and high magnetic flux density for stability of the superconducting coil. However, soldering for interconnecting each double pancake causes current decay, cryogenic coolant loss, and thermal stress. Thus, this paper investigates an improved double pancake winding, named the “jointless double pancake coil winding” and demonstrates the efficacy for minimizing the electrical loss of the high-temperature superconducting (HTS) coil, assembled in the modular double pancake types. It presents a winding method that avoids soldering between the pancake connections and thus removes the primary cause of the electrical loss generated in the existing design. This proposed winding method can effectively achieve zero electrical loss. This paper particularly presents the application of the proposed winding for the HTS-SMES and demonstrates the feasibility and improved functional benefits with reference to the conventional coil. This paper should maximize the operational benefits of using the SMES coil employing the proposed winding method in charge and discharge operations and should increase the effectiveness and efficiency in cryogenic systems.

Analysis of transient state in HTS tapes under ripple DC load current

The paper concerns the analysis of transient state (quench transition) in HTS tapes loaded with the current having DC component together with a ripple component. Two shapes of the ripple were taken into account: sinusoidal and triangular. Very often HTS tape connected to a power electronic current supply (i.e. superconducting coil for SMES) that delivers DC current with ripples and it needs to be examined under such conditions. Additionally, measurements of electrical (and thermal) parameters under such ripple excitation is useful to tape characterization in broad range of load currents. The results presented in the paper were obtained using test bench which contains programmable DC supply and National Instruments data acquisition system. Voltage drops and load currents were measured vs. time. Analysis of measured parameters as a function of the current was used to tape description with quench dynamics taken into account. Results of measurements were also used to comparison with the results of numerical modelling based on FEM. Presented provisional results show possibility to use results of measurements in transient state to prepare inverse models of superconductors and their detailed numerical modelling.

Design study of 4.5 MJ sector-toroidal SMES coil

In continuation of SMES technology development in our centre, design study of a 4. 5 MJ (1.25 kW h) sector-toroidal SMES coil using custom make Rutherford type NbTi cable is reported. The sector- toroid is optimized with six modular type solenoid coils connected in series. The basic module is considered to be solenoid type because of its easier winding technique though it is not the best choice from stress considerations. The coil operating current as well as maximum magnetic field at the inner layer has been determined in order to limit voltage across the coil during discharging mode of its operation and also to minimize the overall dynamic and static load in the cryostat. Due to asymmetric field distribution around the coil, each coil experiences a huge centered force that needs to be arrested with proper support structures. Therefore, extensive magneto-structural stress analysis has been carried out using commercial finite element code ANSYS. The paper describes the magnetic design, three dimensional stress analyses in coil and its support structure during cool-down and energisation, design scheme of sector- toroidal SMES cryostat, etc.

Development of a High-Efficiency Conduction Cooling Technology for SMES Coils

YBCO(YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> ) wires have superior characteristics such as high energy densities, thus allowing the fabrication of large-scale, high power-output superconducting equipment applications. A high voltage is desired to achieve a large power output from a superconducting coil, and is realized by improving the insulating properties of the coil with the introduction of solid insulation. However, because high temperature superconducting wires have high critical temperatures and thermal tolerance compared to metal-based superconducting wires, the benefits offered allow the insulated superconducting coil to be directly cryocooled. In a helium circulation cryocooling system, the aluminum-fabricated transmission heat shields are coated around the surface of the coils to cryocool equally, and are embedded into the transmission heat shields with the conducting pipe allowing helium gas to circulate. We manufactured a conduction cooled model coil of 600 mm class diameter, and have verified the ability to realize a cooling of more than 3 W/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for coil surface heat flux at an operating temperature of 20 K using the demonstration cooling system. In addition, we have also evaluated the electric insulation performance, which is in contradiction to the cooling performance. The conduction-cooled YBCO coil withstood up to DC 13 kV voltages at 20 K.

Unified Control for a Wind Turbine-Superconducting Magnetic Energy Storage Hybrid System Based on Current Source Converters

This paper proposes the unified control for a novel wind turbine-superconducting magnetic energy storage (SMES) hybrid system, where the SMES coil is integrated with the DC link of the current source converter (CSC) fed wind energy conversion system. The unified power and current control schemes are proposed for general grid conditions by designing the proper active damping, the closed-loop grid current regulation, and the decoupled double synchronous frame phase locked loop (DDSRF-PLL). Furthermore, the system operation schemes are proposed and designed for both the normal SMES current condition and the low SMES current condition. The performance of the proposed control schemes are verified by computer simulation.

The Beneficial Role of SMES Coil in DC Lines as an Energy Buffer for Integrating Large Scale Wind Power

Wind energy resources are accounting for an ever-greater portion of the many nations' generation portfolios to address global climate change concerns and reduce carbon dioxide emissions. Increasing the role of wind in the power generation mix, however, presents significant operational challenges in ensuring the grid security and power quality due to the inherent resource variability. This paper addresses the integration of large-scale wind resources into the grid through DC lines incorporating SMES coil: Doubly-Fed Induction Generator (DFIG) type wind power plant linked by line-commutated HVDC with and without SMES is investigated using PSCAD/EMTDC for various operating scenarios. The study demonstrates the effectiveness of applying SMES coil in the DC line for mitigating the wind power intermittency and for improving its dispatchability and quality. Enhanced robustness for AC and DC faults due to the SMES coil and its benefits are also discussed.

Design Study of SMES System Cooled by Thermo-Siphon With Liquid Hydrogen for Effective use of Renewable Energy

In order to use effectively renewable energy sources, we propose a new system, called Advanced Superconducting Power Conditioning System (ASPCS), that is composed of SMES and Fuel Cell-Electrolyzer (FC-EL) in connection with a liquid hydrogen station for vehicles. The new system will compensate the fluctuating renewable energy sources with SMES having characteristics of quick response and large I/O power, and with FC-EL having characteristics of moderate response and large storage capacity. The SMES coil with an MgB2 conductor operated at 20 K is cooled with a thermo-siphon cooling system by using cryogen from the liquid hydrogen station. The necessary minimum storage capacity of SMES is estimated as 50 MJ for compensating output power of 1 MW. A four-pole SMES coil is designed by using stranded cable concept. The design study of the SMES coil composed of the MgB2 conductor and the thermo-siphon cooling system is reported.

Quench Detection and Protection of Cryocooler-Cooled YBCO Pancake Coil for SMES

In this paper, we focus on the quench detection and protection of a cryocooler-cooled pancake coil for SMES wound with a YBCO bundle conductor composed of laminated electrically insulated YBCO-coated conductors. Because the normal-zone propagation velocity is much slower in a high-temperature superconducting (HTS) coil than in a low-temperature superconducting (LTS) coil, the detection of the non-recovering normal zone using a voltage signal is quite difficult. Quench detection is considered to be more difficult during SMES operation because of the noise of the converter or other equipment. Therefore, a quench must be detected using some other method. In the previous paper, we showed that a quench in the coil could be detected by observing the transposition of the current in the bundle conductor caused by local normal transition. In this paper, based on this quench detection method, we investigate the transposition of current and the thermal behavior during the quench detection and the dumping of the stored energy by an external resistance in coils wound with a YBCO laminated bundle conductor for SMES and determine the appropriate stabilizer thickness of the YBCO-coated conductors.

Numerical Simulation of MgB&lt;sub&gt;2&lt;/sub&gt; Superconducting Magnetic Energy Storage Coil

A coupled thermal electromagnetic finite element analysis has been used to numerically simulate the electromagnetic characteristics of an MgB2 SMES coil. Magnetic field distribution data and current density predictions of the numerical model were compared with the literature and with the superconducting properties of explosively consolidated MgB2 samples measured experimentally. The material Jc characteristics were determined by applying Bean’s critical state model on the material magnetisation measurements conducted on a superconducting quantum interference device (SQUID).

Probabilistic assessment of power system transient stability incorporating SMES

This paper presents a stochastic-based approach to evaluate the probabilistic transient stability index of the power system incorporating the wind farm and the SMES. Uncertain factors include both sequence of disturbance in power grid and stochastic generation of the wind farm. The spectrums of disturbance in the grid as the fault type, the fault location, the fault clearing time and the automatic reclosing process with their probabilities of occurrence are used to calculate the probability indices, while the wind speed statistics and parameters of the wind generator are used in a Monte Carlo simulation to generate samples for the studies. With the proposed method, system stability is ”measured”. Quantitative relationship of penetration level, SMES coil size and system stability is established. Considering the stability versus coil size to be the production curve, together with the cost function, the coil size is optimized economically.

Analysis of Current Distribution in Multi-Laminated HTS Tape Conductor for Double Pancake Coil of SMES

A multi-laminated HTS tape conductor has been recently developed to fabricate large double pancake coils. If the HTS tapes are simply laminated to form the conductor, the current distribution in the laminated tape conductor of the coil is unbalanced because of different inductances of all tapes. It is very important to analyze current distributions in the multi-laminated tape conductor used for the double pancake coil for SMES. In this paper, we analyze the current distribution in the tape conductor by using electrical circuit model, and then discuss how to obtain the homogeneous current distribution. One way is to transpose the tape position at both ends of pancake coil so as to arrange the tapes symmetrically. However, this method is not perfectly geometrical symmetry for more than 3 laminated tapes in the conductor. We propose new method to obtain homogeneous current distribution by adjusting gaps between HTS tapes in the conductor. Finally we numerically demonstrate the homogeneous current distribution in the 4-laminated tapes with inserting additional thickness among tapes.