Analytical Modelling of Harmonics in an Exciterless Synchronous Generator

The replacement of the brushless exciter in the synchronous generator has long been desired as a method to increase power density. There are many topologies available that allow the excitation system of a synchronous generator to be combined with the main magnetic circuit, but these topologies have previously only been demonstrated on low power machines. This paper develops an analytical model of an existing exciterless machine topology and uses it to produce an optimized winding configuration to convert an existing, brushless exciter based, generator design to exciterless. Harmonic performance is a key requirement for medium power designs, with strict restrictions placed on manufacturers by grid standards worldwide. Therefore, the focus of the analytical model is to accurately predict the harmonic content of the machine at no-load, including the overall output voltage shape. This is validated experimentally against a prototype machine, and the feasibility of the exciterless topology, for medium power and above applications, is discussed.