Design and implementation of a PI-PBC to manage bidirectional power flow in the DAB of an SST

Abstract

The interest of moving towards more sophisticated power grids and the possibility of having more efficient and reliable power semiconductor devices have enabled the introduction of new concepts in power systems, such as solid-state transformers (SSTs). SSTs are considered to be one of the most relevant elements in the future of smart grids since their functionalities allow for the appropriate integration of distributed generation, renewables, energy storage systems, among others, with traditional power grids. One of the main stages of an SST (a DC-DC stage) includes a dual active bridge (DAB) that enables bidirectional power flow, which is regarded as one of the main advantages over traditional power transformers. This work focuses on proposing a current control strategy based on PI passivity in order to regulate the power flow in a DAB. The proposed controller guarantees the system's stability in a closed loop, keeping its passive properties. In addition, it preserves the simplicity of a PI controller, with high performance and robustness, and it does not depend on the converter's parameters. The performance and effectiveness of the proposed controller is validated through time-domain simulations and experimental results under different power flow conditions, including bidirectional power flow. The results show that the proposed controller has a better performance than classical PI controllers.