Qingquan Qiu

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.

Development of the World's First HTS Power Substation

With the increasing depletion of fossil fuels and growing environmental pressure, the mankind has got known the need to vigorously develop the renewable energy and the energy-saving technology. The high Tc superconducting (HTS) power technology will be very helpful to enhance the stability, reliability, and efficiency and transmission capacity of the power grid which would be dominated by the renewable energy. In this paper, we will report the installation and operation of a 10 kV HTS power substation which includes a 75 m/1.5 kA HTS power cable, a 10 kV/1.5 kA HTS fault current limiter, a 1 MJ/0.5 MVA high Tc SMES and a 630 kVA/10 kV/0.4 kV HTS power transformer.

Development and Demonstration of a 1 MJ High-Tc SMES

A superconducting magnetic energy storage system (SMES), with stored energy of 1 MJ and compensation power of 0.5 MVA, has been developed successfully, and now is operating at the worlds first superconducting power substation at Baiyin National High-Tech Industrial Development Zone, Gansu Province, China. The SMES employs a high Tc superconducting magnet, which consists of 44 pancakes, operates at 4.2 K in liquid helium, and is cooled down by 4 G-M cryo-coolers. The SMES connects to a 10.5 kV power grid by the use of a power conversion system. Since 16 February, 2011, the SMES has been operating reliably, and providing good-quality power for three companies.

Winding Design and Electromagnetic Analysis for a 1250-kVA HTS Transformer

Because high-temperature superconducting (HTS) coils possess low-resistivity, large-current-carrying, and state transition characteristics, the design of HTS transformers is much different from that of conventional ones. The general design of 10.5-kV/1250-kVA HTS transformer is given first. In the electromagnetic design of the 1250-kVA HTS transformer windings via field-circuit coupling simulation, the influence of leakage magnetic field on the critical current of tapes and the circulating current of parallel branches was considered. Moreover, the transient stability of transformer windings combined with superconducting fault current limiter in the HTS power substation is discussed. Based on electromagnetic analysis, the primary and the secondary windings are constructed, and a special transposed method for double pancakes wound with four parallel tapes is proposed. Finally, the current-carrying ability of the primary and the secondary windings is tested in 77 K. Their critical currents are higher than 200 and 3200 A, respectively, which is enough in rated operating condition.

Analysis of Levitation Characteristics of a Radial-Type High-Temperature Superconducting Bearing Based on Numerical Simulation

A two-dimensional (2D) axisymmetric finite-element model was proposed to simulate the levitation characteristics of a radial-type high-temperature superconducting (HTS) bearing. The E-J power law together with an H-formulation was used to consider the superconducting state. The numerical model was successfully implemented using a FORTRAN program. A comparison of the experimental results with the simulation was given to validate the model. It shows that they have good agreement. The electromagnetic behavior inside the HTS bulks was also analyzed. The model presented in this paper can be used to optimize the design of a radial-type HTS bearing.

A Real-Time Measuring and Control System for the World's First HTS Power Substation

The worlds first high-temperature superconductor (HTS) power substation (the substation) for the only power distribution grade has been successfully developed in live grid in 2011 in Baiyin, Gansu Province of China. This 10 kV HTS power substation is an integration of 75 m/1.5 kA HTS power cable, 10 kV/1.5 kA HTS fault current limiter, 1 MJ/0.5 MVA high Tc superconducting magnetic energy storage and 630 kVA/10 kV/0.4 kV HTS power transformer. The HTS power substation is operated automatically by a real-time measuring and control system, and it is not necessary to have anyone on duty. Software is developed by using LabView program. The cooling system providing a low-temperature environment for the cryogenic devices is an independent system, and is also the key part to ensure the run of the substation. The real-time measuring and control system for the substation, which comprehensively measures and controls the related signals of the HTS power substation, is introduced, and the controlling system for the cooling system is described in detail in this paper.

Development of a Combined YBCO/Bi2223 Coils for a Model Fault Current Limiter

Recently, the high-temperature superconducting (HTS) devices and superconducting technologies have become widespread in the field of electric power. The 2G wires are expected to be used in future power applications because it has high properties in high temperature and high magnetic fields. One of the most promising applications for HTS coils in electrical engineering is for high-temperature superconducting fault current limiter. In this paper, the design, fabrication, and experiment of the combined YBCO/Bi2223 coils were described. Nine coils wound with 122 m YBCO tapes and three coils wound with 376 m Bi2223/Ag tapes, were assembled into the combined coils. The YBCO coils were in a noninductance configuration and the Bi2223/Ag coils were in a solenoid configuration. For getting higher resistances and rapid response to the fault current, the structure of the combined coils, the heat stability, and the insulation of the YBCO coils were the main targets in the development of the YBCO coils.

Control and Test of a 0.5 MVA/1 MJ SMES

A 0.5 MVA/1 MJ superconducting magnetic energy storage system (SMES) has been installed in a superconducting power substation. The SMES is designed to compensate active power fluctuations, current harmonics and reactive power of the downstream load. The system configurations and control strategies are described. Experimental and field test results show that the proposed SMES can effectively improve the power quality of the power system.

Design Method of SMES Magnet Considering Inhomogeneous Superconducting Properties of YBCO Tapes

Design of SMES magnet is a complicated process containing many problems such as stability, magnet configurations, and nonlinear characteristic during optimization. In this paper, we first studied the characteristics of considered YBCO tape such as B-J characteristics and inhomogeneous superconducting properties through a series of experiments. To select the best configuration that needs the least YBCO tape, we proposed a new stepped shape configuration of SMES magnet and compared the design of different stepped shape with rectangular cross-section magnet models. The results showed the inner stepped shape and outer stepped shape cross-section models need the least YBCO tape at 20 K and 77 K, respectively. Simulated annealing (SA) is adopted as optimization algorithm to avoid local optimal solution and find global optimal solution. Finally, we optimized a magnet prototype as an example considering all the obtained results in this paper.

Investigation of Flux-Coupling Type Superconducting Fault Current Limiter With Multiple Parallel Branches

The flux-coupling type superconducting fault-current limiter (FC-SFCL) is discussed in this paper. Considering the shortcomings of conventional inductive and resistive SFCLs, two novel FC-SFCLs with multiple parallel branches are carried out. Considering the characteristics of YBCO tapes in 77-K LN2 environment, the design scheme of the HTS module is studied according to the impedance parameters, the number of parallel branches, and insulation distance. Furthermore, the electromagnetic analysis and parameter calculation of the module are performed. In order to identify the status of the HTS module in normal operating, current limiting, and reclosing processes, the status identification method for HTS module is analyzed. Finally, the possible application of FC-SFCL in power grid is discussed.