Robust Control for a Battery Charger Using a Quadratic Buck Converter

In this paper, the quadratic buck converter (QBC) is proposed as competitive alternative to implement a battery charger. Since QBC is a high order system, the required control is designed to follow the conventional constant-current constant-voltage protocol by means of three loops. Namely, 1) an inner-loop operating in sliding mode to control the current of the closest inductor to the input port providing the proper stability of the system, 2) a first outer loop designed to regulate the battery voltage providing the reference of the inner loop, and finally 3) a second outer loop to regulate the battery current modifying the reference of the voltage loop. Proportional Integral (PI) controllers are used in both outer loops, one of them synthesized by means of the robust loop shaping M-constrained integral gain optimization (RLS-MIGO) method, and the other designed using classical considerations for cascaded controllers. Both simulation and experimental results are presented validating the theoretical study and confirming the feasibility of the proposed control by means of analogue electronics.