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A new topology of the active superconducting DC fault current limiter (DC-SFCL) applied in the hybrid AC.DC power supply systems is described. The simulation models of the DC-SFCL and the hybrid AC/DC power supply system are created by using MATLAB SIMULINK and the simulation tests are performed to evaluate the system performance.

A 150 kJ/100 kW conduction-cooled HTS superconducting magnetic energy storage magnet, which consists of 17 double pancake coils and operates at 20 K, was developed and manufactured in the Huazhong University of Science and Technology. To evaluate the thermal characteristic of the magnet, this paper conducts a series of experiments and carries out the loss analyses. When the maintaining time and peak value of the flat top current in the magnet are constant, the maximum temperature rise will first decrease and then increase with the continuous augment of the current ramp rate, and it means that there is a valley value for the maximum temperature rise during an operational cycle time including charging, standby, and discharging stages. Similarly, the total losses, which include the ac heat loss and the resistive loss caused by the joints between every two double pancakes and extra resistance of the high temperature superconducting (HTS) coils, will fall with the increase of the ramp rate to its valley value, and then it will increase with the ramp rate. Experimental results show that the temperature variation of the magnet is in keeping with the heat loss variation. [ABSTRACT FROM AUTHOR]

As superconducting magnetic energy storage (SMES) and battery are complementary in their technical properties of power capacity, energy density, response speed, etc., this paper proposes an SMES-battery energy storage system to stabilize a photovoltaic-based microgrid under different faults. The related theoretical modeling is stated, and the control and coordination methods of the SMES-battery are put forward. Using MATLAB, a comparison of with the SMES-battery and only with the battery is carried out. From the main specifications of the SMES magnet, the ac-loss calculation is also performed. The results show that i) the SMES-battery is better than the battery to timely deal with the transient faults of the microgrid; ii) the SMES-battery enables to ensure a seamless mode-transition for the microgrid under the external fault, and reduce the fault current in the point of common coupling to avoid an unnecessary off-grid under the internal fault; and iii) the SMES magnet's ac-loss power has a maximum value of 380 W, and it is acceptable for the future design of conductioncooled structure and cryogenic system. [ABSTRACT FROM AUTHOR]

This paper suggests a small-scale superconducting magnetic energy storage (SMES) to enhance the transient behaviors of a 100kWgrid-connected photovoltaic (PV) system, and conducts the conceptual design and performance evaluation. Considering the PV system requirements, the stored energy of the SMES is 90 kJ, and theYBCOtapes are adopted to make a solenoid SMES magnet. Based on the genetic algorithm, the magnet parameters including critical current, tape length, parallel and perpendicular magnetic fields are optimized. Using simulation tools, the effects of the SMES on the PV system are assessed, and the electromagnetic properties, stress, and loss of the SMES magnet are analyzed. The results prove that 1) the SMES improves the fault-ride-through capability and realizes an effective protection for the PV system. 2) A relatively large perpendicular magnetic field is found in both ends of the SMES magnet, and the maximum field is induced in the middle of the SMES magnet. 3) The maximum stress of the SMES magnet is acceptable, and the mechanical strength is satisfied. 4) The ac loss is crucial for voltage maintenance performance of the SMES at the fault. Under a short clearance time, the heat accumulation may have a moderate controllability. [ABSTRACT FROM AUTHOR]

In this paper, a flux-coupling-type superconducting fault current limiter (SFCL) is suggested to protect a 15-MW class doubly fed induction generator (DFIG)-based wind farm. Detailed conceptual design and performance evaluation of the SFCL are conducted. From the technical requirements and operational parameters of theDFIGwind farm, a 35-kV/500-A flux-coupling-type SFCL is designed, taking into consideration: 1) the winding type, core selection, and inductance values of the coupling transformer (CT); and 2) the structural style, tape length, and quenching resistance of the superconducting coil (SC). By use of different simulation tools, the electrical and electromagnetic characteristics of the SFCL are evaluated. The results show that the maximum magnetic field of the CT is 2.4 T, and the ac loss of the SC is 0.51W. Not only the electromagnetic properties and loss of the SFCL are acceptable, but also using the SFCL in the wind farm enables to suppress the fault current, compensate the voltage sag, and mitigate the wind power fluctuation. Thus, the robustness of the DFIG-based wind farm against the fault is enhanced, and the effectiveness of the proposed SFCL design is verified. [ABSTRACT FROM AUTHOR]

To model the nonlinear characteristic of the flux linkage for the switched reluctance motor, a modified flux linkage analytical model and a fast model are proposed. The models are based on an original polynomial model which fits the ψ-θ curve at different phase currents by analyzing the error percentage curve of the original model in this paper. The coefficient of the polynomial is discussed for a fast model in order to solve the modeling problems quickly. Then, the electromagnetic torque of switched reluctance motor is calculated by the modified model and the fast model, which agree well with the finite element results. Based on the modified model, the simulation model is built in MATLAB/Simulink. Also, an experimental platform is established to validate the proposed models. [ABSTRACT FROM AUTHOR]

Controlled reactors can adjust the output capacity to stabilize system voltage, control reactive power, and improve system stability according to operating conditions. The design of reactance and control system determines whether a controlled reactor can meet the requirement of stable operation. In this paper, the operating principle of a high temperature superconducting leakage flux-controlled reactor (HTS-LFCR) is introduced. The design of the reactance and the optimal initial turn-on angle of the control system are discussed. An HTS-LFCR is fabricated and tested. The experimental results show that the reactance design values are basically consistent with the experimental tests; when the initial turn-on angle of the control system is 90°, the reactor can achieve a smooth transition from one operating mode to another. [ABSTRACT FROM AUTHOR]

In this paper, a high-temperature superconducting (HTS) loss-free delay network for high-power pulses is performed. Based on the voltage and current pulse experiments carried out at 300 and 77 K, experimental results demonstrate that, under the matched resistive load condition, compared with a normal conducting lossy delay network, the HTS loss-free delay network can effectively reduce the amplitude attenuation of voltage pulses and the front-edge distortion of current pulses. [ABSTRACT FROM AUTHOR]