H^∞ control of boost converters

The tasks of the controller in a PWM power converter are to stabilize the system and to guarantee an almost constant output voltage in spite of the perturbations in the input voltage and in the output load. We propose to design the controller using H^∞ control theory, via the solution of two algebraic Riccati equations. The almost optimal H^∞ controller is of the same order as the converter and has a relatively low DC gain (as opposed to the classical approach of maximizing the gain at low frequencies). In a case study, for a typical low power boost converter, we obtain significantly improved frequency responses of the closed loop system, as compared to classical voltage mode, current mode or feedforward control.