Non-linear magnetic modelling of aircraft variable frequency synchronous generators

It is essential for manufacturers of aircraft electrical equipment to accurately model major components such as variable frequency starter generators (VFSG) prior to integration in an aircraft electrical power system. Although prior work exists on the theoretical approach for modelling motors and generators it is still a challenging problem for engineers to able to integrate complex electro-magnetic models such as VFSG in a simulation to enable behaviour and performance to be effectively and efficiently modelled in a simulator. A particular problem is the trade-off between simulation speed and accuracy when non- linear windings are considered, and this paper considers the impact of non-linear magnetic behaviour on the overall model of a synchronous generator when approximations such as the well known DQ0 axis approach are used. This paper shows a hybrid approach to address this problem by including both winding non-linearities and a three stage VFSG model using DQ0 axis transformations to ensure correct THD behaviour without using a full ABC approach.