Combining Time and Frequency Domain Design in Current Control to Optimize Command and Disturbance Response

Abstract:
This paper presents a model-based design method for current controllers of pulse-width modulated converters. It demonstrates how the command-tracking and disturbance rejection behavior of current controllers must be designed separately via appropriate state-feedback and feedforward paths, as well as feasible references to yield an optimized system behavior. The method features a state-feedback design in the frequency domain that optimizes the load and disturbance voltage response and illustrates important design limitations. The state-feedback design in the frequency domain is effectively linked to the time domain to facilitate a physically understanding of all control design decisions. For optimized, high-bandwidth command tracking, a trajectory filter generates feasible references for the state-feedback control, as well as for command-feedforward. The trajectory filter takes into account the available voltage margin and limits the di/dt of the trajectories to prevent saturation of the feedback controller and eliminate any windup issues. The proposed design method is evaluated based on experiments that validate its wide applicability.