A Review on Flux Estimation Methods for Variable Flux Machine Applications

Permanent magnet variable flux machines offer an additional degree of freedom with adjustable rotor flux. To utilise this additional parameter for efficient control a detailed description of the flux condition in the machine is required. A basis for this is the estimation of magnetic field strength, which is the objective of this work. For the analyses, a simulation was set up to model the machine with variable magnetic flux. The simulation model was used to implement and analyze methods for determining permanent magnet flux. Some methods revealed a strong interdependence between inductances and magnetic strength, making them inapplicable. The methods that proved effective in this work are an extended Kalman filter and the use of information from an additional torque measurement.