A Concentrated Wound Interior Permanent Magnet Machine for Direct-Drive Wind Turbine Applications

摘要

In direct-drive wind turbine systems, intermediate gearboxes are eliminated to increase the efficiency and reliability of the system. This also reduces maintenance downtimes. The direct-drives necessitate the generator to have a low rated speed. Therefore, permanent magnet machines with high number of poles are favourable for direct-drive wind turbine applications. An interior PM synchronous machine (IPMM) offers a number of advantages such as the availability of reluctance torque, extended constant power speed range. These machines also present an economic edge with the reduced use of expensive rare earth magnet materials. This makes this IPM machine a promising candidate for direct drive wind turbine application.This thesis presents a systematic approach to design an interior permanent magnet machine with concentrated windings for direct-drive wind turbine applications. The initial phase of this work investigates and compares the performances of the interior PM synchronous machine with fractional-slot concentrated winding and the distributed winding in stators and the flat-shaped or V-shaped magnets in the rotor respectively. The design criteria are set to achieve a low cogging torque, low torque ripple, and high efficiency. The cogging torque and the torque ripple are reduced by improving the rotor and stator geometry utilizing the Finite Element Analysis. It was found that the fractional-slot concentrated wound interior permanent magnet synchronous machine can provide comparable performance as that of a distributed wound interior permanent magnet synchronous machine and even perform better on attributes like the cogging torque, power density, torque ripple and the copper loss. The fractional-slot concentrated wound interior permanent magnet synchronous machine with flat-shaped magnet structure is constructed to validate the findings experimentally. This thesis is the only detailed literature so far that investigates and presents experimental validation of the performance of a fractional-slot concentrated wound interior permanent magnet synchronous machine as a generator for direct-drive wind turbine system. This thesis also analyzes the dynamic performance of the prototype machine. The result shows that the existing dynamic control strategies of the distributed wound IPM machine can be easily adopted in a concentrated wound IPMM without any significant changes.The work done in this thesis creates a strong benchmark for future work on fractional-slot concentrated wound IPM machines suitable for direct-drive wind turbine application.