A Novel Brushless Synchronous Generator Combining Series Hybrid-Excited and Salient-Pole Wound-Field Sections for Hydropower

This paper proposes a novel axially parallel salient pole hybrid excitation synchronous generator (PSPHESG) for small and medium hydropower (SMHP). To prevent irreversible demagnetization of the permanent magnets (PMs), while improving the power density and reducing the volume compared with those of a conventional electrically excited synchronous generator equipped with an AC exciter, a salient pole series hybrid excitation machine is axially integrated with an electrically excited machine, with the latter serving as the power compensation section. The basic structure and operating principles of the proposed PSPHESG are introduced. Finite-element analysis (FEA) is used to investigate the magnetic field distribution and no-load characteristics. Moreover, the phase angle deviation characteristics and output performances under load are analyzed, showing favorable voltage output capability over a wide load range during steady-state operation. Finally, the anti-demagnetization capability of the PM is studied under field forcing (FF) and de-excitation (DE). The results confirm that the PSPHESG not only provides good constant-voltage capability but also effectively avoids irreversible PM demagnetization during FF and DE, indicating its promising applicability to SMHP systems.