Comparative Study of Relieving-DC-Saturation Hybrid Excited Vernier Machine With Different Rotor Pole Designs for Wind Power Generation

Hybrid excited (HE) machines are a potential solution for wind power generation for their high efficiency from permanent magnet (PM) and good flux regulation ability from flexible field current. However, the principle and machine performance of different structures are diverse, which brings challenges in selection of machine topologies and in the dimensional parameter design. Hence, in this article, two machines with different topologies are presented and analyzed to show their merits and demerits. Both machines have relieving-DC-saturation PMs located in the slot openings, while only one of them has consequent rotor PMs to provide an auxiliary flux and to enhance torque production. In this article, the machine structure and working principle are presented, including the relieving-DC-saturation-relieving effect and air-gap field harmonic analysis. For a fair comparison, under the same outer diameter, rated current density, the dimensional parameters of two machines are optimized with genetic algorithm (GA). Further, the machine performance of the optimal models is compared in terms of torque production, back EMF, voltage regulation ability and speed range. The merits and demerits of both machines are summarized in the conclusion.