Study on Digital Implementation of Full-Order Flux Observer for Induction Motor

Sensorless vector control system based on the full-order flux observer is widely applied benefiting from development of the digital signal processor (DSP). An essential step in the digital implementation is discretizing the continuous observer into the expression which can be implemented by DSP. Forward Euler method (FEM) is simple and easy to work out. However, the discrete full-order flux observer discretized by the FEM losses its performance, especially of precision and convergence, because this discretization method has characters of low precision which will result in poor convergence. In this paper, error and convergence properties of the FEM are analyzed firstly, and then an improved method for the implementation of the discrete full-order flux observer in DSP is proposed. It increases iteration frequency of the observer within a switching period and the iteration step size is equivalent to be decreased. Consequently, precision and convergence of the observed states are improved. Finally, simulation and experimental results verify the effectiveness of the proposed method.