The Smart Grid needs energy storage to cope with the highly volatile energy generated by renewable energy sources. Power converters that employ DAB bi-directional DC-DC converters are commonly used to transfer this stored energy to and from the Smart Grid. To maintain grid stability and ensure good transient performance, fast and accurate control of these converters is required. The aim of this thesis is to design a high performance closed-loop regulator for a DAB converter that can achieve a very fast transient response. To achieve this goal, a dynamic representation of the DAB converter dynamics is derived based on the significant harmonics present in the converter switching signals. It is then identified in this work that deadtime can have a significant effect on converter dynamics, so a series of closed form expressions that predict the effect of deadtime across all operating conditions were derived. The prediction is used to extend the harmonic model, achieving a first order, two-input, small-signal state space model that was verified in simulation and then matched to an experimental DAB converter. This new harmonic model was used to investigate the performance limits of a closed loop P+I (Proportional + Integral) voltage regulator for the DAB converter, and several enhancements to maximise its performance were developed. First, it was found that the controller gains are limited by transport delay, which is inherent to the digital implementation of the controller. Accounting for this delay allowed the maximum possible controller gains to be calculated. Second, it was found that the plant gain changes significantly with operating point, so controller gains are recalculated dynamically across the entire operating range to maintain consistent operation. Third, load current was found to act as a disturbance to the system, severely compromising performance. A feed-forward disturbance rejection algorithm was developed and applied to the closed loop regulator to resolve this problem. The new regulator was tested in a Smart Grid AC load application, where the DAB converter was used as a DC supply for a H-bridge DC-AC inverter. The excellent voltage regulation achieved by the new closed loop controller significantly reduced the output capacitance required to maintain the DAB output voltage under both steady-state and transient conditions. This result offers the potential to eliminate the traditional electrolytic capacitor used in these applications, with associated size, cost and lifetime benefits. All ideas in this thesis were verified on a 1kW prototype DAB bi-directional DC-DC converter
