A PI Based Simplified Closed Loop Controller for Dual Active Bridge DC-AC Converter For Standalone Applications

DAB based inverter (DABI) provides DC to AC conversion with variable input voltage source. The fundamental modulation consists of either dual or triple phase shift modulation. Therefore, it is important to understand the dynamic model for the fundamental dual phase shift modulations before designing a closed loop controller for the DABI. With an accurate dynamic model, the AC output voltage can be controlled in every high frequency switching cycle. Alternatively, the peak switching cycle may be controlled once every line cycle to maintain peak voltage at a desired value. In this work a modified generalized average model is developed for dual phase shift modulation and is applied to control the DABI output AC voltage. Afterwards, a simple PI based closed loop controller is developed based on the derived model for output voltage control. Finally, in order to improve the response time for the PI-only controller, a combined feedback and feedforward controller is proposed which is shown to improve the settling time by 66%. Simulation and experimental results are provided validating the controller performance.