Calculation Of Circulating Current Losses In Stator Bars Of Synchronous Compensator With Different Operating Conditions

Synchronous compensator is an important reactive power compensation equipment for ultra-high voltage power grid,stator bar is an important part of synchronous compensator,the related optimal design and manufacturing technology is an important issue in the design of synchronous compensator.The stator core of the synchronous compensator is longer,540 degree transposition of stator bar is common.With the leakage flux of the stator slot and the end,the stator bar of the synchronous compensator produce different leakage inductance electromotive force on each strand.There is a potential difference between the circuit formed by any two strands.Then the circulating current will be formed and the circulating current loss will be produced,which will seriously affect the service life and operation safety of synchronous compensator.In this paper,taking a 300 MVar large capacity synchronous compensator as an example,the circulating current loss of stator bar are calculated when synchronous compensator is in the motion of different load conditions.Aiming at the problem of calculation of circulating current loss in 540 degree transposition of stator bar in synchronous compensator,the equivalent strand loop method is proposed.Slot mutual inductance leakage reactance for 540 degree transposition and 540 degree viod transposition of stator bars in synchronous compensator is deduced by equivalent area method.Based on Kirchhoff’s law and Ampere’s loop theorem,a set of equations for calculating the strand current of stator bars in a single slot is presented.The equivalent calculation method of slot mutual inductance leakage reactance with 540 degree void transposition is combined with particle swarm optimization algorithm.On this basis,PSO-based optimization algorithm for circulating current loss of void transposition is proposed.Taking the circulating current loss of stator bars in synchronous compensator as the goal,void transposition length and position of stator bar as an optimization variable to optimize the design of stator transposition bar in synchronous compensator,double-layer isomeric transposition mode is proposed which can reduce the circulating current loss of stator bar effectively.Calculating the current and circulating current losses of single slot stator bar strands by FEM with 540 degree transposition mode and double-layer isomeric transposition mode respectively,and compared with the calculating results of equivalent strand loop method,the accuracy of equivalent strand loop method was verified.The circulating current loss of stator bars is calculated by equivalent strand loop method when synchronous compensator is with different operating conditions.