Comparison of universal field oriented (UFO) controllers in different reference frames

The principle of the universal field oriented (UFO) controller, operating in an arbitrary reference frame, is applied to a CRPWM inverter. Due to its high degree of generality,the UFO controller is compatible with rotor, stator, and air-gap flux field oriented control. The authors compare the stability regions and the steady state performance of these three types of controllers applied to the same machine. The rotor flux based controller has been selected as the basic reference. Digital simulation results are carried out to show that the performance of the complete UFO system, i.e., combined direct and indirect UFO, in a nonrotor flux based reference frame leads to a robust high performance drive with no dependency on machine parameters in steady state