Design of a 12-MW HTS Wind Power Generator Including a Flux Pump Exciter

© 2016 IEEE. A flux pump (FP) exciter injects dc current into the higherature superconducting (HTS) field coils of an HTS rotating machine without a slip ring and current leads. When designing a large-scale HTS generator with integrated FP exciter, the coil inductance, field current, and time constant need to be optimized for better performance of the machine. In this paper, a 12-MW HTS wind power generator with integrated FP exciter was designed. The essential parameters of a 12-MW HTS generator were optimized using the Taguchi method, targeting the minimization of weight and volume of the generator, the length of HTS wire, and the inductance. In particular, the FP exciter was adopted for supplying dc current to the HTS field coils without the power supply and the slip ring. The magnetic field distribution was analyzed using the 3-D finite-element method. The induced dc current and charging and discharging times of the FP exciter were compared with the metal current leads, for confirmation of the effectiveness of the FP exciter. The detailed results of the HTS generator design were discussed in detail

Design and Heat Load Analysis of a 12 MW HTS Wind Power Generator Module Employing a Brushless HTS Exciter

Brushless high-temperature superconducting (HTS) flux pump exciters, which enable large currents to be injected into a superconducting circuit without requiring a power supply, slip ring, and current leads, are promising candidates for HTS rotating machine application. This paper outlines the design and heat load analysis of a 12-MW HTS wind power generator module employing a brushless HTS exciter. The 12-MW HTS generator module and the HTS exciter were simulated using the 3-D finite element method. The module design of the generator was focused on reducing the heat load and inductance per rotor pole for application of an HTS exciter. A highly permeable ferromagnetic material was used to increase the magnetic flux density incident on the HTS stator wire of the exciter, even with a large radial gap between the rotor and the stator, and hence increase the injected current. Based on the electromagnetic simulations, the design of the module was confirmed, and the iron loss of the exciter was calculated. Then, the conduction and radiation heat loads were simulated. The induced dc current value and ramping time of the DC current at the HTS stator wire of the exciter were calculated. The detailed results of the module with the HTS exciter were discussed, and the results obtained in this paper are useful in designing large-scale HTS generators. © 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Development of a brushless HTS exciter for a 10 kW HTS synchronous generator

HTS synchronous generators, in which the rotor coils are wound from high-Tc superconducting wire, are exciting attention due to their potential to deliver very high torque and power densities. However, injection of the large DC currents required by the HTS rotor coils presents a technical challenge. In this paper we discuss the development of a brushless HTS exciter which operates across the cryostat wall to inject a superconducting DC current into the rotor coil circuit. This approach fundamentally alters the thermal load upon the cryogenic system by removing the need for thermally inefficient normal-conducting current leads. We report results from an experimental laboratory device and show that it operates as a constant voltage source with an effective internal resistance. We then discuss the design of a prototype HTS-PM exciter based on our experimental device, and describe its integration with a demonstration HTS generator. This 200 RPM, 10 kW synchronous generator comprises eight double pancake HTS rotor coils which are operated at 30 K, and are energised to 1.5 T field through the injection of 85 A per pole. We show how this excitation can be achieved using an HTS-PM exciter consisting of 12 stator poles of 12 mm YBCO coated-conductor wire and an external permanent magnet rotor. We demonstrate that such an exciter can excite the rotor windings of this generator without forming a thermal-bridge across the cryostat wall. Finally, we provide estimates of the thermal load imposed by our prototype HTS-PM exciter on the rotor cryostat. We show that duty cycle operation of the device ensures that this heat load can be minimised, and that it is substantially lower than that of equivalently-rated conventional current leads