Uncertainty and Disturbance Estimator-Based Robust Tracking Control for Dual-Active- Bridge Converters

Abstract

External disturbances, system uncertainties, and various load characteristics, e.g., deadtime effect, computation time delay, circuit parameter uncertainty, and the constant power load (CPL), can lead to tracking errors that even result in instability in the output voltage of dual-active-bridge (DAB) converters. To address those challenges and improve the output performance, an uncertainty and disturbance estimator (UDE)-based robust voltage control scheme is proposed in this article. First, a generic dynamic model for DAB converters is proposed based on the converter output current to simplify the controller design, which integrates the DAB circuit model with the phase-shift control scheme. Then, the UDE-based voltage controller is presented based on the proposed model, and the stability performance is discussed in detail. With the CPLs, the output impedance of the UDE-controlled DAB converter is also modeled for the first time to show the stability boundary. Based on the derived stability criteria, the design of the UDE controller is summarized. A series of comparative experiment studies has been conducted, and the results prove that the proposed scheme can notably improve the voltage tracking performance and extend the stability boundary of the DAB converters when feeding CPLs even under significant parameter uncertainties.