Multisampled Digital Average Current Controls of the Versatile Buck–Boost Converter

The coupled-inductor buck-boost converter is a versatile dc-dc converter, which is suitable for performing different roles within the hybrid power systems. Its multiple advantageous features include noninverting voltage step-up/step-down characteristic, high efficiency, wide bandwidth control, ability to control the input and output voltages and currents, and so on. All the existing current control approaches for this type of converter are based on analog control implementation, which allows achieving high closed-loop bandwidth. However, analog control limits the possibilities for applying the advanced control schemes and algorithms for achieving smooth operating mode transitions. This paper proposes two digital current control strategies for a versatile buck-boost converter: a predictive average current control and a multisampled average current control. Both the proposed digital control strategies ensure fast tracking of the control set point, low steady-state error, and a practically undegraded dynamic response of the system in comparison with the analog average current control. The theoretical analyses have been validated by means of simulations and experimental tests performed on a 48-V 600-W purpose-built prototype.