Design of voltage model flux observer

The voltage model flux observer can accurately estimate the stator flux when operating at high speed. However, at low speed this estimation is highly sensitive to the stator resistance variation. Also the observer needs voltage sensors for actual voltage measurements and becomes less accurate if command voltages are used, especially beyond the linear modulation region, where the command voltages are no longer equal to the actual ones. These problems are addressed through the design of a closed-loop voltage model flux observer that is completely insensitive to stator resistance variation, and thus it can work at high as well as low speed. The proposed observer also does not require any voltage signal information, either command or measured one, thus making it more accurate even beyond the linear modulation region without adding any voltage sensors. The observer stability has been verified. Simulation and experimental results are presented to validate the proposed algorithm.