Improved virtual flux observer based on orthogonal feedback compensation suitable for direct power control application

In the case of PWM rectifier unsteady virtual flux amplitude caused by grid voltage instability. We can´t achieve constant flux amplitude saturation limit. In order to eliminate the errors caused by direct current drift and initial value in voltage model based flux estimation of direct power control system, a new virtual flux observer based on virtual flux linkage to be perpendicular to grid voltage, it depends on the adaptive controller to adjust the compensated reference flux, for the fast and accurate tracking of flux changes caused by the grid voltage fluctuations. The new simple structure of flux observer is easily achieved in the engineering without proportion integral regulator. Experimental results show that the orthogonal feedback compensation theory can effectively restrain the saturation feedback and direct current drift while dynamic error is diminished, improve the precision of virtual flux estimation efficiency, and also improve the directional accuracy of system as well as its dynamic and static performance.