Influence of asymmetric-paths winding on electromagnetic force of variable speed pump storage generator-motor

Abstract

Stator asymmetric-paths winding of variable speed pump storage (VSPS) generator-motor can solve the problem of mismatch of unit speed, capacity and outlet voltage. However, different winding connection schemes will lead to the change of magnetomotive force (MMF) asymmetry of each branch, and then affect the electromagnetic force of generator-motor. In order to explore the effect of this winding type on the electromagnetic force, stator asymmetric-paths winding's MMF and electromagnetic force of 336 MW VSPS generator-motor is derived. Waveforms and harmonic contents of the stator asymmetric-paths winding MMF of the equal-pitch and unequal-pitch schemes are analyzed. Under the consideration constraints of factors such as minimizing MMF asymmetry and electromagnetic vibration, a reasonable asymmetric-paths winding scheme with unequal pitch is determined It is concluded that asymmetric-paths winding scheme with pitch of 14-15-16 can effectively weaken the low-order MMF harmonics and reduce the electromagnetic force under the limitation of asymmetric-paths winding form. The finite element model of VSPS generator-motor is further developed, and the electromagnetic force amplitude and spatial and temporal distribution characteristics under 6 winding schemes are calculated to verify the accuracy of the calculation model. The results of the study can provide technical support for the development of localized VSPS generator-motor.