Stability Analysis of DAB Converters with Boundary Control for Electrical Vehicles

Advanced automotive electrical systems employ multi-voltage level ac and dc systems as well as electrical mechanism systems that have unique characteristic, dynamic and stability problems due to the time dependency of converters. Power electronic converters and motor drives in tightly regulated automotive systems often behave as constant power loads which have negative impedance characteristics. Classical control methods often focus on the constant resistance load where the linearizing analysis is applying in time domain. In this paper, based on the DAB DC-DC converter, circular switching surface (CSS) strategy which achieves step-up and step-down operations by controlling the four transistors, is described to avoid the instability of constant power load. This CSS control strategy is a nonlinear method to observe the switching actions of different states in phase plane (V
_out
, i
_L
). This report has described the control law of this proposed closed loop control method. Meanwhile, some simulation results and experimental results have indicated the feasibility of CSS control strategy.