Modeling of PWM converters is derived from the conventional averaging technique. In Series Resonant Dual Active Bridge (SRDAB), the conventional averaging method fails as the current flowing through the resonant tank of the SRDAB is alternating in nature.

This research proposes a generalized average model for SRDAB converter with variable phase shift control. This proposed model uses the output filter capacitor voltage, resonant capacitor voltage, and resonant inductor current as state variables. The dc component and the fundamental component of state variables are used to develop the proposed model. The transformer's leakage resistance is considered for more accurate modeling. With the help of the model proposed, the average model and the small signal model of the converter are derived and compared with the switching converter model time domain simulation. The beat frequency dynamics often seen in the resonant converters could be predicted using this proposed model. The analytical expression for small signal control to output transfer function for phase shift control is derived, which aids in the control loop design.

This model is further extended to other control schemes available for SRDAB and developed a unified mathematical model for varying control schemes. In the unified model, by replacing the values of the variables according to the control schemes (SPS, EPS, DPS, or TPS), one can easily get the proper model, which could help in further designing and understanding the dynamics. The proposed model is verified with an experimental setup for a load of 1.5 kW using Software Frequency Response Analyzer (SFRA) tool available in the F28379D microcontroller.