Adaptive dynamic control of a bi-directional DC-DC converter

Abstract

It is important for a bi-directional dual active bridge DC-DC converter to maintain a stable output voltage under input voltage and output load changes, as well as providing a fast transient step response. However, designing a voltage regulator that achieves this performance is challenging, and requires a precise analytical converter model. This paper develops such a model, firstly by analysing the response of the converter to the individual harmonics of the phase shifted square waves that modulate the bridges, and then by combining these responses into a small signal model that accurately describes the dynamic performance of the converter. From this model, an adaptive voltage regulator is then proposed that adjusts its proportional and integral gains as the steady state operating conditions vary, to achieve the design target of a slightly underdamped response at all times. The theoretical analysis is confirmed by matching simulation and experimental results.