Liye Xiao

Recent Progress of Power Application of Superconductor in China

The significant progresses in high Tc superconducting wires or tapes have excited a great deal of research interests in power application. This paper will review the recent progresses of power application of superconductor in China. An improved bridge-type fault current limiter was tested and a 10.5 kV/1.5 kA demonstrator has been operated at a substation in Hunan Province in 2005. A 75 meter, 10.5 kV/1.5 kA three phase HTS cable has been installed and operated at the Changtong Cable Headquarter in the end of 2004, and a 30 meter, 35 kV/2 kA HTS power cable was installed at substation and has been operated since July 2004. A 10.5 kV/400 V/630 kVA HTS transformer has been installed and operated at TBEA electric factory in 2005. A 500 kj/150 kVA SMES unit was developed and tested. 1.0 MJ/0.5 MW SMES will be installed in a power grid in 2006. Besides, a new kind equipment of fault-current-limiting SMES is being developed and a 100 kJ/25 kW prototype has been made and tested.

Development of a 630 kVA Three-Phase HTS Transformer With Amorphous Alloy Cores

This paper describes design and operation of a three-phase HTS power transformer with capacity of 630 kVA operated in liquid nitrogen of 77 K for primary/secondary voltages of 10.5 kV/0.4 kV. The windings were wound by hermetic stainless steel-enforced multifilamentary Bi2223/Ag tapes. The structures of primary and secondary windings are solenoid and double-pancake respectively. Cryostat is made from electrical insulating materials with room temperature bore for commercial amorphous alloy core. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests. The ac losses were calculated and measured by method of conventional transformer. The HTS power transformer successfully operated in a live power grid.

Design of a High Temperature Superconducting Generator for Wind Power Applications

High temperature superconducting (HTS) generator was promising in the wind power applications for its advantages in the weight, size and thermal stability against load fluctuations, especially in the “direct-driven” design. A 100 kW generator was proposed for the demonstration of the feasibility of using HTS in 10 MW wind turbine generators. The electromagnetic design and optimization of the rotor were done using finite element method (FEM). The excitation coil of the rotor was designed considering variable working conditions. According to the numerical results, a number of suggestions in the design and winding techniques of the superconducting rotor were proposed.

Recent Main Events in Applied Superconductivity in China

With strong support from Chinese government bodies such as the National High Technology Research and Development Program of China, National Natural Science Foundation of China and the National Basic Research Program of China, the field of applied superconductivity in China has been developed in different areas. Especially in the fusion application area, the first fully-superconducting tokamak, EAST (Experimental Advanced Superconducting Tokamak), has been successfully constructed and commissioned in the last two years. Based on the requirement from the ITER project, high performance Bi-2223 HTS tape, and Nb3Sn and NbTi strands have been developed as well. In the area of HTS applications for electric power systems, R&D has been focused on superconducting power cable, superconducting magnetic energy storage, superconducting transformer, superconducting fault current limiters. In this paper, the recent progress in applied superconductivity in China is reported.

HTS Power Technology for Future DC Power Grid

The growing environmental pressure resulting from the use of fossil fuels is leading mankind to make a transition from the use of traditional energy sources to that of renewable energy based clean energy. Because renewable energy has the feature of instability, it thus brings significant challenges on real-time power balance and power dispatching. Therefore, to secure the power supply, the grid needs to be upgraded by the selection of a reasonable grid structure and operation mode. In this paper, a multiple-level direct current (dc) loop grid, which would be the suitable mode for the future power grid, is suggested. Then, the high-temperature superconducting (HTS) dc power technology such as the HTS dc power cable and dc fault current limiter for the future power grid are discussed. We also report on the test and operation of a 360-m/10-kA HTS dc cable that is being built and would be used for an electrolytic aluminum plant of Zhongfu Group in Henan Province, China.

Fabrication and Tests of a 1 MJ HTS Magnet for SMES

In this paper, the design, fabrication and tests of a I MJ HTS magnet for SMES was presented. The magnet was fabricated by BSSCO tapes, it consisted of 44 pancakes, the inner diameter of the winding is 400 mm, the outer diameter is 568 mm and the height is 648 mm, the inductance is 6.38 H and the rated operation current is 560 A at 4.2 K. The tests show the magnet could be operated at the design parameters. The magnet will be used for the 1 MJ/500 kVA SMES unit which will be demonstrated at a 10 kV substation in Beijing.

The effect of ZrSi2 and SiC doping on the microstructure and Jc-B properties of PIT processed MgB2 tapes

We investigated the effect of ZrSi2 and SiC doping on the microstructure, critical current density Jc and flux pinning of Fe-sheathed MgB2 tapes prepared by the in situ powder-in-tube method. Heat treatment was performed at a low temperature of 650 °C for 1 h. The phases, microstructures and flux pinning were characterized by means of x-ray diffraction, scanning electron microscope, magnetic and transport property measurements. It was found that the tapes doped with nanoscale SiC had the best pinning performance, while the ZrSi2 powder showed a similar improved field dependence of Jc compared with undoped samples. Jc values for the SiC doped samples were enhanced by two orders of magnitude at 4.2 K in magnetic fields above 8 T. At 4.2 K and 10 T, the Jc reached ~1.5 × 104 A cm−2. Moreover, the critical temperature for the doped tapes decreased slightly (<1.2 K). Microstructural analysis shows that very good grain connections or/and grain refinement were obtained for the doped tapes. The mechanism of the enhancement of the flux pinning is also discussed.

Evaluation of the Performance of BTFCLs for Enhancing LVRT Capability of DFIG

Performance of three kinds of bridge-type fault current limiters (BTFCLs) for enhancing low-voltage-ride-through (LVRT) capability of DFIG is evaluated in this paper. The common BTFCL can effectively enhance the LVRT capability of DFIG. However, the fault-current-limiting inductor (FCLI) is periodically inserted into the stator circuit under normal operation for compensating power losses of the FCLI. The periodically insertion of the FCLI induces stator voltage spikes, which causes significant stator flux and electromagnetic torque oscillations. One feasible way to solve this problem is to use an additional current-regulating circuit (CRC). However, the additional CRC increases hardware cost, reduces reliability of the whole system, and induces more power losses. To solve this problem, a BTFCL with bypass resistor (BTFCL-BR) is presented. The BR absorbs the majority of the current harmonics during normal operation and eliminates the stator voltage spikes. The flux and electromagnetic torque oscillations can thus be significantly reduced. The performance of three kinds of BTFCLs is evaluated by simulation and experimental studies on a typical 1.5 MW wind turbine driven DFIG system and a 2 kW DFIG prototype. By simulation and experimental evaluations, it seems that the BTFCL-BR approach is the most promising solutions among the three kinds of BTFCLs.

Design of a 380 m DC HTS Power Cable

High temperature superconducting (HTS) power cable is an effective power transmission utility with large capacity, high efficiency, and low loss, especially in DC power transmission. This paper describes the design of a 380 m HTS power cable with rated current of 10 kA for an aluminum electrolysis enterprise. The power cable connects the rectifier at a substation at one end with the bus bar of an aluminum electrolysis plant at the other end at Henan Zhongfu Industrial Co. LTD. The power cable will be energized in late of 2010. The design of the cable conductor, cryogenic envelope, termination, refrigeration, and online monitoring system of the 380 m HTS power cable are discussed in this paper.

Development of a 10 kA HTS DC Power Cable

The new energy revolution which will be dominated by renewable energy will need to develop a corresponding new power grid. Based on the characteristics of renewable energy resources, and the stability problem of AC network, it was proposed that the DC-based transmission grid should be developed in the future. The high Tc Superconducting (HTS) power cable will be a competitive candidate for large-capacity power transmission of renewable energy. In this paper, the progress of the development of a 360 m/10 kA HTS DC power cable is presented, and the prospects of HTS cable is discussed.