发电电动机静止变频器起动低频运行阶段的谐波特性

Harmonics Characteristics of Generator/Motor Starting With Static Frequency Converter During Low Frequency

磁动势与电磁转矩谐波特性的准确计算是对发电电动机起动运行性能进行分析的前提。在发电电动机静止变频器起动低频运行物理过程分析的基础上,建立了此运行阶段电流计算的精确模型,通过实例对电流谐波特性进行了定量计算;然后以此模型推导出了计及时间谐波影响的定子磁动势表达式,分析了不同时间谐波对定子基波磁动势的影响。最后,在计及转子凸极效应影响的情况下,推导出了低频运行过程中电磁转矩解析计算公式,样机电磁转矩的有限元计算结果验证了解析公式推导的正确性。计算结果表明:5次、7次时间谐波对定子磁动势影响最大,而11次、13次与29次、31次影响近似;6次谐波转矩幅值达到恒定分量的44.94%,12次谐波转矩幅值超过恒定转矩分量的30%。

Accurate calculation of magnetomotive force（MMF） and electromagnetic torque harmonics, is the premise of performance analysis for generator/motor starting system. Based on physical process analysis of generator/motor starting with static frequency converter（SFC） operating at low-frequency, the accurate currents calculation model was established under the process, and the currents harmonics characteristic was calculated quantitatively with a living example. Then, the stator MMF expression was derived from the current accurate model within considering the influence of time-harmonic, and it is analyzed that different time-harmonics affects on the stator fundamental MMF. At last, the accurate calculation formula of electromagnetic torque was derived within considering the effect of rotor salient pole, and a prototype electromagnetic torque calculated with the finite element method verified the correctness of the analytic formula derivation. The results show that the effect of the 5th and 7thtime-harmonics on stator MMF is the most serious, and that of the 11 th and 13 th are close to the 29 th and 31 th time-harmonics. And the 6th amplitude of harmonic torque accounts for 44.94% of constant torque, the 12 th harmonic torque is over 30% of that.