Adaptive control; dc-dc power converters; fuel cells; nonlinear control systems Adaptive control systems; Asymptotic stability; Backstepping; Closed loop systems; Controllers; Electric inductors; Electric inverters; Fuel cells; Fueling; Lyapunov functions; Lyapunov methods; Nonlinear control systems; Power converters; Power generation; Two term control systems; Voltage control; Voltage regulators; Adaptive back-stepping; Adaptive backstepping control; Adaptive Control; Average currents; Converter system; Load variations; Output voltage regulation; Proportional integral; DC-DC converters