Passivity-based stabilization of converter in DC power supply system using feedforward control

This paper proposes a passivity-based stabilization control of a converter in a DC power supply system using feedforward (FF) control to improve output frequency impedance characteristics that satisfy the Nyquist stability criterion. The principle is that the output impedance is designed to be passive, and the system is sufficiently stable for any filter impedances. The new design principle for the proposed stabilization method consists of four steps. First, the state feedback (FB) control gains with a mitigated integral compensator are designed to possess a good response characteristic according to the optimal control. The designed characteristic of the output impedance may not be passive at a lower frequency band due to an essential characteristic of an integral compensator. Second, the integral characteristic is modified and a resistive characteristic is added to the band by a new FF control design based on a fitting method to make the total characteristic passive and to ensure stability. Third, the correction coefficients are tuned to eliminate a deviation between the measured and reference output voltage values at transient operations. Finally, the system passivity is re-checked, and a resistive characteristic is re-added using the FF control design if a nonpassive band exists. The effectiveness of the proposed method to render the system passive and stable is investigated and validated using simulated and experimental results.