不对称负载对汽轮发电机磁场畸变及功角的影响

Influence of Asymmetrical Loads on Magnetic Field Distortion and Power Angle of Turbo-generator

大型汽轮发电机是电力系统的重要组成部分,其稳定性直接影响了电力系统的安全运行。在建立二维电磁场时步有限元模型的基础上,对一台1 407 MVA汽轮发电机的空载、额定负载及不对称负载运行工况进行深入研究。分析了汽轮发电机不同运行工况下磁场的变化,给出了发电机负载不对称工况下磁密偏移角度的计算方法,通过磁密偏移角度来定量的研究发电机磁场畸变的变化规律。研究了在汽轮发电机负载不对称工况对应的不同负序含量下发电机内功率因数角及功角的变化规律。研究结果表明汽轮发电机在带不对称负载时,不仅磁场发生偏移与畸变并且内功率因数角、功角均随负载不对称发生相应变化,得出的仿真结果与理论分析结果相一致,为发电机在负载不对称工况下磁场的研究及故障判断提供一定的理论基础。

Large turbo-generator is an important part in power systems and its stability directly affects the safe operation of the power system. On the basis of establishing two-dimensional electromagnetic field-circuit-motion coupled time-stepping finite element model,the no-load condition,rated load condition,and asymmetric operation condition of a 1407 MVA turbo-generator was further studied in the paper. Firstly,the paper analyzes changes in different conditions and definition calculation method of flux density deviation angle under asymmetrical load of generator. The variation law of the generator magnetic field is studied by the flux density deviation angle. The inner power factor and power angle are calculated under the condition of asymmetric load operation. The paper analyzes the change of inner power factor and power angle. The result indicated that turbo-generator not only the magnetic field displacement happened but also the change of inner power factor,power angle happened. The simulation results are consistent with the theoretical analysis. Therefore,it provides with certain theoretical basis for asymmetric operation condition and fault judgment of the generator.