An Augmented State Space Modelling Approach for DC-DC Converter Start-Up in Closed Loop

The continuity of power supply for disturbance-sensitive loads is ensured by replacing faulty converters while the load remains operational. The start-up transient of the incoming converter is crucial for uninterrupted power delivery to the load as well as the stability of the overall system. Existing small-signal approaches for DC-DC converters are of insufficient for modelling this start-up accurately, due to its inherent large-signal nature. This paper addresses this issue by proposing a modelling approach for the closed-loop start-up of DC-DC converters, using state space augmentation. The proposed method appends the state space of a system operating in closed loop by considering the control input to be an additional state. This appended or augmented model facilitates accurate prediction of the transient behaviour during closed-loop start-up. An analytical modelling algorithm is presented for a generic system. Subsequently, the proposed approach is instantiated for a boost converter operating in closed loop. The accuracy of the proposed approach is demonstrated through simulation results as well experiments on a laboratory prototype.