Analysis of Additional Eddy-Current Copper Losses in Large Converter-Fed Hydropower Generators

Abstract

This paper investigates the effect of converter operation on AC copper losses in the stator and damper windings of a large hydrogenerator. Stator currents are computed using finite element simulations. The computed current waveforms are used as an input to estimate the AC copper losses in the stator due to converter operation using an analytical approach. Damperbar losses are calculated directly in the finite element analysis. The generator is simulated with a two-level voltage source converter and a three-level neutral-point-clamped converter topology. Different carrier frequencies are used to investigate their effect on the AC copper loss. Methods for handling these additional losses are discussed and analysed.