Effect of Types and Orders of Electromagnetic Field Finite Element Meshes on Power Communication Harmonic Parameters Calculation Results of Tubular Hydrogenerators

In generator design field, waveform total harmonic distortion (THD) and telephone harmonic factor (THF) are parameters commonly used to measure the impact of generator no-load voltage harmonics on the power communication quality. Tubular hydrogenerators are considered the optimal generator for exploiting low-head, high-flow hydro resources, and they have seen increasingly widespread application in China's power systems recent years. However, owing to the compact and constrained internal space of such generators, their internal magnetic-field harmonics are pronounced. Therefore, accurate calculation of their THD and THF is crucial during the analysis and design stages to ensure the quality of power communication. Especially in the electromagnetic field finite element modeling analysis of such generators, the type and order of the finite element meshes may have a significant impact on the THD and THF calculation results, which warrants in-depth research. To address this, this study takes a real 34 MW large tubular hydrogenerator as an example, and establishes its electromagnetic field finite element model under no-load conditions. Two types of meshes, five mesh densities, and two mesh orders are analyzed to reveal the effect of electromagnetic field finite element mesh types and orders on the calculation results of THD and THF for such generators.