A proportional-integral (PI) controller can be used to maintain the measured current component at its desired value. The pulse width modulation of the VFD defines the switching of the transistors according to the stator voltage reference which is the output of the PI current controller.
Originally developed for high-performance systems, FOCs are also increasingly attractive for low-cost applications due to their smaller motor size, lower cost, and lower power consumption. As low-cost, high-performance MCUs continue to be introduced, FOC continues to replace the lower-performance univariate scalar volts-per-hertz (V/f) control.