L.Y. Xiao

Development and Test of 10.5 kV/1.5 kA HTS Fault Current Limiter

Superconducting Fault Current Limiter (SFCL) is an attractive appliance for modern electrical power system. A 10.5kV/1.5 kA three-phase HTS fault current limiter was developed by IEE, CAS. This improved rectifier-type SFCL with HTS coil of 6.25 mH is going on a demonstrated long-term reliable operation in a real 10.5 kV substation located in Hunan, China. In a three-phase-to-ground short circuit test of grid, the prospective fault current of 3.5 kA was limited to 635 A at the pre-setup short-circuit point successfully

Development of HTS AC Power Transmission Cables

Along with the rapid growth of the national economy in China, the electric utility is faced with an ever rising demand for electricity and the problem to solve large capacity power transmission. Under the support of the High Technology Research & Development Program of China, a 1.5 kA/10.5 kV 10-m long 3-phases HTS transmission power cable and a 75-m long, 3-phase, 10.5 kV/1.5 kA HTS power cable have been developed successfully by the Institute of Electrical Engineering, Chinese Academy of Sciences. The 75-m long HTS power cable operates now at a local live distribution grid of 6.6 kV to supply electric power for Changtongs factory in Baiyin, Gansu Province. The cable operates stably and reliably over 7000 hours since December 2004.

Development of solenoid and double pancake windings for a three-phase 26 kVA HTS transformer

We prepared 6 coils from the stainless steel-enforced multifilamentary Bi2223/Ag tapes and studied their electromagnetic behavior for a three-phase 26 kVA (400 V/16 V, 37.5 A/937.5 A) transformer. The primary windings were solenoid coils consisted of 4 helically wound layers, and the secondary windings were consisted of 24 double pancakes connected in parallel with 3 layers, the strand of 6 windings was consisted of two parallel transposed multifilamentary tapes. A numerical analysis has been developed to predict the DC and AC behavior of the coils based on measurements of short samples and tested coils at 77 K. A comparison is made between the experiment and model calculation.

Research on Stability of

Magnesium diboride (MgB2) shows a wide application prospect in the field of low field DC application for its relatively simple structure and rather higher critical temperature than LTS. With the development of MgB2 composite superconductor manufacturing technology and cryogenic technology, developing conduction cooled superconducting MRI system with MgB2 composite superconductor is becoming increasingly feasible. An MgB2 superconducting magnet for MRI was developed. The MgB2 superconducting magnet is used to investigate the fundamental scientific problem of the MRI main magnet, including field uniformity and stability, influencing factors of MgB2 composite superconductor on field uniformity and stability. The superconducting magnet consists of 2 solenoids wound with MgB2 wire with the length of 60 m. The magnet has an outer diameter of 169 mm, an iron core diameter of 135 mm, and air gap of 32 mm. The superconducting magnet is fabricated and tested. The central magnetic field reaches 1.0 T when the current of the MgB2 magnet is 290 A. The central magnetic field is 0.39 T when the current of the MgB2 magnet is 100 A. In this paper, the minimum quench energy, the quench propagation velocity and the minimum propagation zone of the MgB2 composite conductor are measured. Main magnet for MRI with MgB2 composite superconductor is analysed and proposed, including magnet design and test results. By theoretical modeling and simulation, the detailed quench propagation of the magnet is further analysed. Finally, the stability criteria of conduction-cooled MRI magnet are established.

{\rm MgB}_{2}

The design and test of High Temperature Superconducting (HTS) coils for a three-phase 10.5 kV/1.5 kA HTS fault current limiter (FCL) are described. It is well known that the critical current (Ic) of HTS materials is very sensitive to the orientation of fields. In the design of HTS coils, the value of the perpendicular component of magnetic field (Bperp) should be reduced, and the coils should be wound and jointed easily. In order to enlarge the current carrying capacity of the coil, the double pancakes in the coils were connected in parallel. Based on the field distribution in the coil and the current distribution in each double pancake, the design of the coil was optimized. Three coils wound with Bi-2223/Ag tape have been developed and tested in liquid nitrogen

Superconducting Magnet for MRI

Close circuits made of Fe and composite sheathed, mono- and multi-filament MgB2 wires were fabricated and tested in liquid He and conduction cooling environments for the demonstration of persistent current operation in such as the magnetic resonance imaging (MRI) magnets. Persistent current switches and superconducting joints were designed and installed in the circuits. The decay time of the captured magnetic field in the coil and joint resistance were measured. According to the results, the resistance of the closed circuit at low temperature can be less than 10−13 Ω, showing a potential for application in the currently develop MgB2 MRI systems. The causes of the circuit resistance were also discussed.

Design and Test of High-

The critical performance of YBCO tape with inhomogeneous superconducting properties was simulated by use of a bad point distribution model and the Gaussian distribution model. The critical current and n value of the whole HTS tape was analysed. The reliability of the simulation was verified with the experimental data. The results of the two simulation models were compared each other. The influence of inhomogeneous properties on the critical performance of YBCO HTS tape was proved by simulation results which are helpful for the simulation of superconducting devices based on YBCO HTS tapes.

T_C

This paper presents the damping torque analysis of an energy storage system (ESS) control in a multi-machine power system. The objective of the analysis is to examine the effect of the ESS control on the power system small-signal stability. Firstly in the paper, a systematic procedure to establish a linearized model of the multi-machine power system with the ESS installed is presented. Secondly the damping torque contribution from the ESS control, including the normal voltage control functions and the supplementary damping control function, is derived. Finally an example multi-machine power system installed with a battery energy storage system (BESS) is given in the paper. Results of damping torque analysis are confirmed by the computation of system oscillation mode and non-linear simulation.

Superconducting Coils for a Three-Phase 10.5 kV/1.5 kA Fault Current Limiter

Magnesium diboride shows a wide application prospect in the field of low field DC application for its relatively simple structure and rather higher critical temperature than LTS. With the development of composite superconductor manufacturing technology and cryogenic technology, developing conduction cooled superconducting MRI system with composite superconductor is becoming increasingly feasible. An superconducting magnet for MRI was developed. The superconducting magnet is used to investigate the fundamental scientific problem of the MRI main magnet, including field uniformity and stability, influencing factors of composite superconductor on field uniformity and stability. The superconducting magnet consists of 2 solenoids wound with wire with the length of 60 m. The magnet has an outer diameter of 169 mm, an iron core diameter of 135 mm, and air gap of 32 mm. The superconducting magnet is fabricated and tested. The central magnetic field reaches 1.0 T when the current of the magnet is 290 A. The central magnetic field is 0.39 T when the current of the magnet is 100 A. In this paper, main magnet for MRI with composite superconductor is analysed and proposed, including magnet design, test results, and field uniformity.

Close circuit test of MgB2 coil with superconducting joints and a persistent current switch

An extended power angle concept based control scheme of doubly fed induction generators (DFIGs) is proposed to operate in place of the conventional PQdq control scheme during the grid fault ride-through (FRT) in this paper. In contrast to the PQdq control, the proposed control has a way better capability to support the terminal voltage of DFIG during the fault period, so that it can help DFIG ride through severe grid faults more efficaciously. The extended power angle of DFIG is defined firstly and then the mechanism of DFIG transient behaviors is revealed based on the understanding of the transient characteristics of the defined power angle. The new control solution of DFIG is designed and verified afterwards. In the paper, an example of 16-machine 5-area power system with 2 grid-connected DFIGs is presented to demonstrate the effectiveness of the proposed control strategy when applied in the large-scale power systems during the system disturbance. Simulation results show that both the capability of FRT of the DFIG and the transient stability of the whole power system are greatly enhanced by the application of this control scheme compared with the PQdq control method.