An Improved-Discrete-Time Model based Equivalent Series Inductances Identification Method for Quad-Active Bridge Converters

In this paper, an improved-discrete-time model (IDTM) for quad-active bridge (QAB) converters is derived at first, which can accurately describe dynamic behaviors with considering equivalent series resistances (ESR), and obtain pole values of high-frequency chain current (HFCC) and load voltages. Then, an accurate equivalent series inductances (ESL) identification method based on IDTM is proposed, which uses the discovered mutual weakening effect to improve the accurate of the identification value. Moreover, proposed a variable-step approximation method to reduce the complexity of solving nonlinear equation systems in ESL identification process. Finally, a simulation and hardware-prototype platforms are conducted for validation. The results indicates that the proposed IDTM can accurately describe dynamic behaviors and pole values during voltage and load transient stages, and achieve a maximum 20.99 % error reduction in comparison to previous average model. Compared with the short-circuit ESL direct-measurement method, the proposed IDTM-based ESL identification method can reduce the estimation errors of the HFCC and the load voltage by up to 66.05%.