A low-speed linear harmonic generator for grid-tied and stand-alone operation using hybrid excitation topology

Since intermediate mechanical conversion mechanisms for speed, torque and motion conversion can be entirely eliminated, the direct-drive wave power generation attracts more and more attention. Among various proposed generators, the permanent-magnet (PM) vernier generator is considered as a viable solution for the wave energy harvesting. This generator can efficiently harness this low-speed and high-power energy source via a so-called vernier effect by utilizing the effective harmonic magnetic field. However, since only PMs are engaged for field excitation and the harmonic magnetic field is adopted, it is incapable to provide a flexible voltage control and power factor improvement. Moreover, the voltage regulation is incredible high. The purpose of this paper is to design a linear harmonic generator for producing electricity in a wave farm. Except for the PM excitation, the proposed generator is equipped with a set of DC field winding for the hybrid excitation. With this merit, the proposed generator exhibits a satisfactory performance for voltage regulation and power factor improvement which is desirable for both grid-tied and stand-alone operation.