Magnetic Energy Storage Coil Research Articles

Analysis on the Effect of Magnetic Energy Storage on the Stability Parameters of a Wind Generator Connected System

The usage of superconducting storage medium for the improvement of system stability is studied in this paper. A Superconducting Magnetic Energy Storage coil (SMES) is used along with the wind energy connected system. The grid connectivity is maintained with the help of converter unit, controlled using fuzzy logic. The system model is simulated on MATLAB/SIMULINK environment and the variations of parameters of the generators are studied.

MEST: A new Magnetic Energy Storage and Transfer system for improving the power handling in fusion experiments

A new magnetic energy storage scheme is studied for improving the power handling in fusion experiments: it can be applied both to tokamak or RFP experiments to supply the poloidal superconducting coils and can efficiently support the operation of the Central Solenoid (CS), without the need for resistive switching networks, thus with the advantage of energy dissipation avoidance. The basic idea, presented with reference to the CS circuit, is to provide an additional Superconducting Magnetic Energy Storage coil (TC), pre-charged along with the CS one to the same current value and then to transfer step by step the energy from one to the other and vice versa during the different phases of the plasma pulse, via switched capacitor. The principle is applied to the case of a Fusion-Fission Hybrid Reactor, based on Reversed Field Pinch configuration operated exploiting the flux double swing.

Voltage Sag Compensation using DVR based Superconducting Magnetic Energy Storage Coil with Pi Controller

Voltage sag is an primary energy satisfactory situation for which the dynamic voltage restorer (DVR) is known as an mighty gadget to mitigate them. The Dynamic Voltage Restorer (DVR) is fast, bendy and effective option to voltage sag hindrance. SMES science has the abilities to carry actual vigor storage attribute to look after consumers from the grid voltage fluctuations. The DVR can restoration the load voltage within few milliseconds. A few configurations and manipulate ways are proposed for the DVR. To clear up this trouble, super conducting magnetic power storage (SMES) situated dynamic voltage restorer (DVR) is introduced to preserve patrons from the grid voltage fluctuations. Because of its excessive vigor density and fast response, it's selected as the vigor storage unit to beef up the compensation ability of DVR. The paper concentrates on efficiency advantages of adding power storage to vigor digital compensators for utility purposes. Simulation results have been presented to illustrate and realize the performances of DVR below voltage sags stipulations. The results got by simulation using MATLAB established the effectiveness of this gadget in compensating voltage sags with very rapid response (relative to voltage sag time).

Eddy-Current Losses of a HT-SMES Coil Under Controlled and Uncontrolled Discharge Conditions

This paper presents an analytical approach of eddy-current loss in a high temperature superconducting magnetic energy storage coil based on finite-element algorithm and numerical circuit analyses. A solenoidal coil with step-shaped cross-sectional shape is introduced to reduce the total eddy-current loss of the whole coil by diminishing the eddy-current losses located at two coil ends. Two coil-current-dependent formulas are derived to estimate the eddy-current loss, e.g., 294 J for a 1.2 H/880 A Bi-2223 solenoidal coil in a 1000 V/500 kW constant-power energy discharge process and then the uncontrolled energy discharge process.

Pareto optimal design of sectored toroidal superconducting magnet for SMES

A novel multi-objective optimization design approach for sectored toroidal superconducting magnetic energy storage coil has been developed considering the practical engineering constraints. The objectives include the minimization of necessary superconductor length and torus overall size or volume, which determines a significant part of cost towards realization of SMES. The best trade-off between the necessary conductor length for winding and magnet overall size is achieved in the Pareto-optimal solutions, the compact magnet size leads to increase in required superconducting cable length or vice versa The final choice among Pareto optimal configurations can be done in relation to other issues such as AC loss during transient operation, stray magnetic field at outside the coil assembly, and available discharge period, which is not considered in the optimization process. The proposed design approach is adapted for a 4.5MJ/1MW SMES system using low temperature niobium–titanium based Rutherford type cable. Furthermore, the validity of the representative Pareto solutions is confirmed by finite-element analysis (FEA) with a reasonably acceptable accuracy.

Design optimization of superconducting magnetic energy storage coil

An optimization formulation has been developed for a superconducting magnetic energy storage (SMES) solenoid-type coil with niobium titanium (Nb–Ti) based Rutherford-type cable that minimizes the cryogenic refrigeration load into the cryostat. Minimization of refrigeration load reduces the operating cost and opens up the possibility to adopt helium re-condensing system using cryo-cooler especially for small-scale SMES system. Dynamic refrigeration load during charging or discharging operational mode of the coil dominates over steady state load. The paper outlines design optimization with practical design constraints like actual critical characteristics of the superconducting cable, maximum allowable hoop stress on winding, etc., with the objective to minimize refrigeration load into the SMES cryostat. Effect of design parameters on refrigeration load is also investigated.

Evaluation of Conduction Cooling Effect of Cryocooler-Cooled HTS Coils for SMES Application

In recent years, the quality of high-temperature superconductors (HTS) has been improving. Our goal is to apply an HTS coil to superconducting magnetic energy storage, because an HTS coil is more thermally stable than a low-temperature superconductor coil owing to high thermal margin during its transition to the normal state and its high thermal capacity at a high operational temperature. On the other hand, to enhance the reliability and safety of an HTS coil, it is necessary to establish a stability criterion to prevent thermal and mechanical damages during a quench. Therefore, we have to clarify the thermal behavior of a cryocooler-cooled HTS coil assuming practical applications. In this study, we evaluated the cooling effect using a numerical simulation and thermal conduction experiments. The numerical simulation was based on the finite element analysis, and the thermal conduction experiments were carried out on a model coil wound with electrically insulated copper and stainless steel laminated tapes. These had the same shape and dimensions as YBCO tape, assuming an application to an superconducting magnetic energy storage coil. We focused especially on the cooling effect of a winding with paraffin impregnation compared with that of a dry winding.

Use of a High-Temperature Superconducting Coil for Magnetic Energy Storage

A high temperature superconducting magnetic energy storage device (SMES) has been realised using a 350 m-long BSCCO tape wound as a ‘‘pancake’’ coil. The coil is mounted on a cryocooler allowing temperatures down to 17.2 K to be achieved. The temperature dependence of coil electrical resistance R(T) shows a superconducting transition at T = 102.5 K. Measurements of the V(I) characteristics were performed at several temperatures between 17.2 K and 101.5 K to obtain the temperature dependence of the critical current (using a 1 µV/cm criterion). Critical currents were found to exceed 100 A for T < 30 K. An electronic DC-DC converter was built in order to control the energy flow in and out of the superconducting coil. The converter consists of a MOS transistor bridge switching at a 80 kHz frequency and controlled with standard Pulse Width Modulation (PWM) techniques. The system was tested using a 30 V squared wave power supply as bridge input voltage. The coil current, the bridge input and output voltages were recorded simultaneously. Using a 10 A setpoint current in the superconducting coil, the whole system (coil + DC-DC converter) can provide a stable output voltage showing uninterruptible power supply (UPS) capabilities over 1 s.

Quasi-stationary magnetic fields of 60 T using inductive energy storage

A pulsed magnet for the generation of fields up to 60 T using inductive energy storage has been built, tested and used for experiments at the Grenoble High Magnetic Field Laboratory (GHMFL). The pulse magnet system consists of a magnetic energy storage coil, made from aluminum of rectangular cross-section with a warm bore diameter of 1.1 m. Inside the warm bore is a smaller high-field magnet made from copper wire with a cold bore diameter of 24 mm. An electrical supply network consisting of a shock alternator, transformer and a rectifier provides the storage coil with a maximum dc current of 120 kA. High-current circuit breakers then direct the stored energy into the high field magnet. For safety and redundancy, two independent monitoring systems control the energy transfers. The design layout of the magnet system and the generation of pulses with fields up to 60.3 T with a pulse duration of 100 ms is described.

Using a superconducting magnetic energy storage coil to improve efficiency of a gas turbine powered high speed rail locomotive

The US Federal Railroad Administration has been pursuing the use of locomotives with an on-board prime mover for high speed rail. Such systems would not require the added cost of rail electrification on top of the rail bed modifications. The prime mover runs a synchronous generator, with the output rectified to feed a DC bus. Adjustable speed drives control the traction motors. However, gas turbines run efficiently over a narrow speed range and a relatively narrow power range. The addition of a superconducting magnetic energy storage coil can improve overall system performance. The SMES coil is charged whenever the locomotive is in regenerative braking mode and whenever the prime mover is producing more power than is needed to maintain the desired speed down the track. The chief benefits to such a scheme are: (1) better acceleration at high speeds, (2) reduced prime mover power rating and weight, (3) reduced railbed cost due to reduced weight (4) reduced trip time and (5) improved fuel efficiency.

Experiment of force-balanced coil for magnetic energy storage

Higher magnetic field is of great advantage to superconducting magnetic energy storage because it promises a compact device. However, it does not affect the serious problem of huge electromagnetic forces caused by high magnetic fields and large coil current. Electromagnetic stresses, reaching as much as several hundred bars, thus become a major factor in determining whether a large-size strong magnetic field system can be established. In order to solve this problem, we have proposed the force-balanced coil (FBC) concept that reduces the huge centering electromagnetic forces by balancing them with the hoop forces caused by the toroidal current. Then we designed and fabricated a small-size superconducting FBC system to demonstrate the FBC concept. It was successfully excited up to near rated current. It is shown that the FBC system has the potential for simplifying the supporting structures and making the facility compact. © 1999 Scripta Technica, Electr Eng Jpn, 128(3): 82–91, 1999

Flow reduction by AC losses for a forced flow superconducting coil with a cable-in-conduit conductor

The forced flow superconducting coil especially made from a cable-in-conduit conductor (CICC) is applied for large-scale devices such as fusion magnets because it has high mechanical and electrical performance potential. It has merits for application for pulsed operation coils such as fusion magnets and superconducting magnetic energy storage coils because of excellent thermal and hydraulic performance. When there is heat generation in the coil due to the AC losses, the CICC has the advantage of being able to remove heat due to the large wet perimeter. Inlet flow reduction is caused by the heat generation on the forced flow coil. The inlet flow reduction provides a limit to the stable pulsed operation of the coil. The models are proposed to evaluate the flow reduction by AC losses due to the pulse operation comparison with the experimental data. The models include the viscosity of the supercritical helium and have good agreement with the experimental data. In addition, the stable operation condition of the pulse coil is also discussed. It can predict the stable conditions of the long pulse operations which are required for fusion and superconducting magnetic energy storage coils.

An evaluation of the inlet flow reduction for a cable-in-conduit conductor in pulsed operation

The cable-in-conduit conductor (CICC) is applied for large devices, such as the fusion magnets, because it has a high mechanical and electrical performance potential. Also, CICC has advantages when applied for pulsed operation coils, such as the fusion magnets and superconducting magnetic energy storage coils, because of its thermal and hydraulic performance. Superconducting coils made from CICC have a cooling path and the coolant of the supercritical helium circulates through the inside of the CICC. When the coil has heat generation due to the AC losses, the CICC has the advantage of being able to remove heat due to the large wet perimeter. The inlet flow reduction is caused by the heat generation of the conductor. The inlet flow reduction provides a limit to the stable pulsed operation of the coil. The inlet flow reduction is measured and discussed for the CICC in this paper. The design criteria of the inlet flow reduction is introduced for the CICC. The zero flow temperature is defined to achieve this purpose. The initial flow rate can be estimated by this criteria, which is applicable for the forced flow conductor, as well as for CICC.

Experiment of Force-balanced coil for Magnetic Energy Storage

Higher Magnetic field is of great advantage to Superconducting Magnetic Energy Storage because it promises a compact device. However, the serious problem of huge electromagnetic forces caused by high magnetic fields and large coil current, still remains. Electromagnetic stresses, reaching as much as several hundred bars, thus become a major factor in determining whether a large sized strong magnetic field system could be established. In order to solve this problem, we propose the force-balanced coil (FBC) concept that reduces the huge centering electromagnetic forces by balancing it with the hoop forces caused by toroidal current. Then we designed and fabricated a small size superconducting FBC system to demonstrate the FBC concept. It was successfully excited up to near rated current. It is shown that the FBC system has a potential for simplifying the supporting structures and making the facility compact.

Power control applications on a superconducting LVDC mesh

The behavior of a high-current, low-voltage DC system is studied. The DC system is made up of superconducting cables connected in a meshed configuration. The system could be made up of several large rectifiers feeding hundreds of small inverters connected to points in one or more AC systems. A unique aspect of this superconducting configuration is power transmission, at the optimal generator voltage level. This voltage level is also close to the subtransmission system voltage, eliminating the need for high-voltage insulation and transformers. A reduced system with one rectifier feeding three inverters is studied. The ability to control the output power from the inverters, both locally and globally, is demonstrated. Power control on the circuit with the addition of a superconducting magnetic energy storage coil is also studied. The large inductance of the coil changes the dynamic response of the system and requires a modification of the control system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Application of a superconducting coil for transient stability enhancement

Abstract Transient stability is an important part of power system design and operation. This paper presents a method to augment the transient stability by using a superconducting magnetic energy storage system. A conventional Graetz bridge converter provides an ideal interface between the three-phase power system and the superconducting coil. This makes power exchange in the superconducting coil fast and controllable. With appropriate gating to the thyristors of the converter, power can be drawn and stored in the magnetic field or vice versa. A mathematical model for the superconducting magnetic energy storage coil with a converter interface is presented. The developed model is integrated with an AC power system by using diakoptical techniques. Two types of control schemes with the generator rotor speed deviation as an input signal to the controllers have been studied on three different power systems. Finally, a comparative study between the dynamic shunt braking resistor method and the superconducting magnetic energy storage method was carried out on a 4-generator, 6-bus system. The computer simulation results reveal that the transient stability enhancement with the superconducting coil is superior to that of the dynamic braking resistor.

Ohmic heating losses in cryoresistive pulsed energy storage aluminium inductors for electromagnetic launchers

Analytic procedures are developed for calculating the ohmic heating loss for various cryoresistive magnetic energy storage coil configurations that are used to deliver periodic short huge bursts of energy to electromagnetic launchers (railguns). Simple geometries such as long solenoids, continuous winding toroids, low aspect ratio dipoles or straight wire are considered as examples. The effect of cabling on reducing eddy current losses is addressed in detail.

Design of the BPA superconducting 30 MJ energy storage coil

The design of a superconducting magnetic energy storage coil is presented. The purpose of this coil is to stabilize low frequency power oscillations in long high voltage ac power lines. The practical application for this specific coil will be the installation in the Pacific intertie between Washington State and Los Angeles, California. The guiding principles of the design are performance, fabrication economy and reliability.