Research on magnetic field state analysis of a nonsalient pole synchronous generator

This paper is based on the definition of minor asymmetric degree and the relative position of the magnetic field. The relative position of the magnetic field is the angle between the positive and negative sequence magnetic fields. The corresponding relationship between the nonsalient pole synchronous generator steady performance and the magnetic field state is discussed when the generator operates at minor asymmetry. To analyze this corresponding relationship, the Taylor expansion formula with Lagrange remainder and symmetrical components is adopted. We study the relationship between the armature current and the relative position of the magnetic field, deducing the armature current expressions with second-order remainders. The law of the armature voltage is also obtained by phasor analysis. As an example, this paper executes two-dimensional finite element numerical calculations on a nonsalient pole synchronous generator. The result shows that the numerical calculation agrees with the deduced expression, which verifies the correctness of the expressions. In the meantime, during the process of deducing the expressions, a method of calculating the positive and negative sequence currents is proposed and their effective range is offered. When the generator works at maximum overvoltage and maximum undervoltage, the specific value of the relative position of the magnetic field is presented. This paper has important implications for generator running and protection.