Sliding mode and current observer‐based direct power control of dual active bridge converter with constant power load

Abstract

This article presents a bidirectional isolated DC-DC dual active bridge (DAB) converter, with an improved control strategy under constant power load (CPL) conditions. Major applications of DAB are in solid-state transformers (SSTs), energy storage systems, dc-microgrid, and electric vehicle, where it feeds other converters, which act as a CPLs. CPLs have negative impedance characteristics, thereby, have a destabilizing effect and impact the dynamics and stability of power converters feeding them. Maintaining the dc-link stability and obtaining a robust control with enhanced dynamic performance is a significant challenge. This paper proposes a sliding mode control method for DAB feeding CPL in its output dc-link. A sliding mode controller is designed to employ direct power control and maintain a constant output voltage in dc-link for various loading conditions. Additionally, to remove the output current sensor, an output current observer is proposed for improving the reliability and decreasing the cost. The proposed method improves the transient performance, with robust control over parameter mismatch when CPL is connected to the dc-link. The transient performance and output voltage regulation with the proposed control technique are simulated with a 3 kW DAB converter in MATLAB/Simulink environment. Furthermore, the same proposed control scheme is validated experimentally with various loading conditions.