This paper presents a method of improving the optimal calculation speed of the cake superconducting magnetic energy storage coil. The optimal size of the cake superconducting magnetic energy storage coil at a given total length of strip is obtained. The calculation speed of genetic algorithm and particle swarm algorithm when calculating the optimal coil size is analyzed and compared. Simulated results show that particle swarm algorithm converges faster than genetic algorithm. Experimental results verify the correctness of the simulated ones.
This article analyzed the losses from the saturated iron-core superconducting fault current limiter (SISFCL) which could be potentially applied into a Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) network. The mathematical model of SISFCL and the loss computation on High Temperature Superconducting (HTS) parts have been performed based on the FEM (finite-element method) combined with H-formulation solved by the COMSOL. Before the FEM modelling of SISFCL, the fault current statues were modeled using PSCAD. The operation performance of SISFCL was simulated as well based on the electromagnetic characteristics analysis, and the power dissipations in the HTS coils of SISFCL were calculated. Results demonstrate even with a DC system, there were certain amounts of loss happened in the HTS coils of SISFCL, if the SISFCL encountered a considerably high fault current.
In order to meet the requirement of ocean energy power generation, a novel linear rotary permanent magnet machine (LRPMM) is proposed with E-type stator structure and interlaced poles. The adjacent interlaced PM poles in the circumferential direction are staggered half pole pitch in the axial direction. The optimization design of LRPMM is analyzed by analytical calculation method and 3-D finite element method (FEM), and the best optimization variable values are achieved. Compared with the results of the traditional topology analyzed by 3-D FEM, the electromagnetic characteristics are increased and the amplitudes of the cogging torque and detent force are reduced. An energy storage system of LRPMM is built, which can improve the effective utilization of wave energy and tidal energy.
Research in the field of superconductivity mainly works in the liquid nitrogen temperature zone. If power electronics are also integrated at low temperatures, power devices have more favorable operating characteristics and a heat dissipation environment. Compared with room temperature, the possibility of device switching may cause performance or even damage. This paper presents a technical concept of a liquid nitrogen immersion cooling Cryogenic Power Electronics Building Block (CPEBB) module device. We can freely choose models according to actual needs and build different low-temperature DC-DC circuit modules and low-temperature AC-DC circuit modules.
REBCO coated conductors have outstanding performance in large scale applications. This paper investigates the adiabatic stability of a Bitter-like HTS magnet, which is stacked by REBCO annular plates and insulators with same inner and outer diameters interactively. In the model, this HTS magnet is magnetized by flux pump, and the induced screening current in the annular plates are equivalent to the superposition of concentric ring circuits. We calculate the flux change under heat disturbance, and investigate its adiabatic stability at different size and operating temperature. The anisotropic character of the critical current of REBCO is considered in the simulation.
In this paper, we introduce an equivalent circuit axisymmetric model to estimate the ramping loss on high-temperature superconducting (HTS) coils with different co-wound materials during the charging process. The ramping loss is the joule loss which is caused by the radial current in HTS coils. It is founded that the material with lower resistivity could produce more radial currents. According to the simulation results, the ramping losses are almost same in quantity. The ramping loss needs to be considered carefully as soon as possible before designing large no-insulation HTS coils or magnets.
With higher magnetic field, the imaging quality and signal-to-noise ratio of MRI system will be significantly improved. The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) has announced a project, which is supported by the Chinese Academy of Sinences, to design a 14T MRI magnet with a 900 mm warm bore and comprised of Nb3Sn Rutherford cables, the homogeneity of the magnetic field is better than 0.5 ppm in a 22 cm diameter spherical volume. This paper is focusing on the introduction of the structural design of the 14T MRI magnet systems, including the coils, main frame, cold shield, dewar, pre-tension and supporting structures. In addition, the preliminary mechanical analysis results of the structure systems are performed.
The post spacer has been used to support the operation of 1000 kV DC Gas Insulated Transmission Line (GIL) for the ITER neutral beam injector. It was considered that the conductivity gradient design along the spacer surface notably suppressed the electric field distortion. In this paper, the electric field distribution of post spacer under 1000 kV dc voltage stress was analyzed and the surface conductivity gradient was applied to optimize the surface electric field distribution. The results indicated that the optimization method with surface conductivity gradient can uniform the electric field distribution along the surface of post spacer.
Flux pumps are a type of wireless energizing device for superconducting systems. The dynamic resistance voltage in the flux pump are the main source for powering the superconducting system. But it can induce undesirable DC current in the circuit of flux pump. This paper discusses how to remove the induced undesirable DC current and improve the performance of the transformer-rectifier flux pump through the optimization of its circuit.
To limit the fault grid current in urban distribution network when a three-phase-to-ground fault occurs in the conventional cross-linked polyethylene (XLPE) power cable joint (CCJ), this paper presents a novel superconducting fault current limitation (FCL) scheme by using a superconducting cable joint (SCJ). The basic principle, circuit modeling and distribution network integrated with the SCJ are presented in detail. Then intensive study is conducted without and with the proposed novel SCJ scheme. The simulation results obtained show that the harmful large fault grid current can be largely reduced by using the proposed SCJ when a grounded fault occurs in the CCJ. Thus the operating environment of the cable trench can be maintained without causing large area power off.
To improve the dynamic performance of doubly fed induction generator (DFIG) based wind turbine during grid voltage swell, this paper presents a novel combinational high-voltage ride-through (HVRT) scheme by using a rotor-side superconducting fault current limiter (SFCL) and a DC-link brake chopper. The basic principle, circuit modeling and control strategies of the SFCL and chopper are presented in detail. Then the comparative study between the proposed SFCL-chopper-based combinational scheme and a SFCL-based scheme is conducted. The simulation results obtained show that the stator voltage, rotor current and DC-link voltage behaviors of the DFIG during grid voltage swell are significantly improved.
In order to reduce the energy storage cost under multiple-line distributions, this paper investigates a new interline DC dynamic voltage restorer (IDC-DVR) scheme with one superconducting coil shared among multiple compensating circuits. An improved DVR chopper assembly is used to connect the single coil with multiple power lines, and thus to satisfy with independent energy exchange requirement of any line to be compensated. The feasibility of the proposed scheme is technically verified to maintain the transient voltage stability in multiple-line voltage swell and sag cases.
The current distributions are analyzed in the Bi2223 tapes of the superconducting bipolar DC energy pipeline with the HTS bipolar DC cables cooled by the transferred liquid natural gas (LNG), with the focus on the three dimensional (3D) modeling of the helical type of HTS tapes. It is especially important to improve the utilization of the HTS tapes by making the currents uniformly distribute among the tapes. Based on the E-J power law [1], the current distributions in both straight and helical Bi2223 tapes of the double-core bipolar DC cables are calculated by two-dimensional and three-dimensional models respectively with the commercial software COMSOL Multiphysics. The results indicate that the current distributions in the straight tapes are not uniform with the highest value being 40% higher than the lowest one for the sample case, where the bipolar voltages are ±110 kV and the current is 1 kA. Whereas the currents in the helical tapes are much more uniform. Both parallel and perpendicular magnetic fields on the helical tape surfaces are evaluated.
The electromagnetic fluctuation occurred in the HTS stator magnet owing to the alternating magnetic field and its harmonic component of rotor in the synchronous wind turbine generator (SWTG). It is a potential risk results in the quench of HTS stator magnet. To address this problem, we applied a no-insulation (NI) magnet technology to the HTS racetrack coil to inhibit the thermal runaway utilizing its outstanding self-protection characteristic and tolerance of over-current. In this study, we focus on investigating the feasibility of the NI HTS racetrack coil, in the practical application of MW-class SWTG. Hence, first, an electrical and thermal coupling numerical model using partial element equivalent circuit (PEEC) and finite element method (FEM) is established. Based on this model, the influence of electromagnetic fluctuation on the thermal and current behaviors of the NI HTS winding during the operation of STWG, was clarified. Further, the influences of turn-to-turn contact resistance of NI racetrack coil on the quench characteristic under various electromagnetic fluctuations were discussed. According to these results, the relationship between the rotation speed of STWG and the turn-to-turn contact resistance of the NI racetrack coil was estimated.
This paper proposes a new hybrid-excited doubly salient permanent magnet machine (HE-DSPMM). The proposed machine employs the PMs in both the yoke and slot openings of the stator, and the concentrated PM flux can effectively enhance the torque capability of the machine. Moreover, by injecting the dc-biased sinusoidal current into the armature windings, the proposed machine can achieve the flux regulation without the field windings. The topology and operation principle of the proposed machine are described. Then, the electromagnetic performance of the machine is investigated based on finite element analysis. The results show that the proposed machine has the high torque capability and flexible flux regulation ability.
This paper investigates methods to increase the energy storage density of superconducting flywheels. The circumferential and radial stresses suffered by the three flywheel models at the same speed are analyzed and compared. The maximum energy storage densities that can be achieved by these models are calculated. Unequal thickness layering and applying compressive stress to the outermost layer can effectively improve the energy storage density of superconducting flywheels.
This paper focuses on the rotor thermal design of the axial flux permanent magnet synchronous machine (AFPMSM) with housing water-cooling. By adapting the effect of disc rotor self-ventilation, an enhanced cooling method has been innovated to optimize the temperature distribution of the rotor in AFPMSM. Two scenarios will be created to compare their influence on cooling enhancement of rotor with the diverse types of fins, the annular fin and the rectangular fin, each will be installed separately to the internal surface of housing. There is a significant effect by using this method in all types of AFPMSM with housing cooling, especially for multi-rotor ones. The results of CFD show that the effectiveness of annular fins is essentially enhanced, with 25% more heat dissipation achieved.
The liquid hydrogen Storage System (LHSS) combined superconducting magnetic energy storage (SMES) have both features of power-type and energy-type energy storage, and is capable of providing power grid auxiliary services. This paper analyzes basic structure of LHSS combined SMES. Requirements for participating in grid auxiliary services and the VSG control strategy are also analyzed in this paper. A novel two layer control strategy which focus on upper layer energy control and lower layer power control is proposed in this paper. A study case is given to verify the effectiveness of the proposed control strategy.
A hybrid stator pole memory machine (HSP-MM) with direct current (DC) bias magnetization is developed in this paper. By introducing the concept of zero-sequence current magnetization, the DC magnetizing winding used in the traditional DC magnetizing MM is eliminated, which improves the utilization rate of internal machine space and the overall torque density. The re/demagnetization of low coercion force (LCF) permanent magnet by DC bias pulse enables HSP-MM to obtain the flexibility of flux regulation. The topology and adjustment flux principle of HSP-MM are depicted and addressed. The electromagnetic characteristics of the HSP-MM at different magnetization levels are analyzed and investigated, which demonstrates that the proposed machine has the good ability of flux regulation.
This article introduced one special cryogenic cooling system for one specific HTS magnet. The system flow chart is drawn, and the main components are analyzed and designed. The performance of the system was evaluated by calculating heat leakage and cooling start-up time, by which approach the technical path to achieve predetermined goal.
