Performance study of smart transformer based on Backstepping-Sliding Mode Control with integral action

This paper proposes a Backstepping-Sliding Mode Control (BS-SMC) design with the aim to improve the dynamic performance of the Smart Transformer (ST) in the distribution grid. This controller combines both Backstepping and Sliding Mode controller’s advantages. Moreover, to mitigate the chattering phenomenon of the SMC, an integral action is introduced to the traditional sliding surface. This combination guarantees an automatic estimation of unknown or uncertain parameters of ST, especially in the presence of intermittent and irregular Renewable Energy Sources (RES) in the distribution grid. Additionally, it enables the improvement of the controller’s robustness against RES voltage and system parameter variations. A comparative study between the proposed controller and existent controllers, namely PI and SMC controllers, is established, and the superiority of BS-SMC is proved. Moreover, simulations are carried out under normal operation mode and in the presence of parameter variations. The obtained results confirm the effectiveness of the proposed controller and prove the enhanced performance of BS-SMC controller as well as its high robustness against source voltage and ST parameters variations compared to PI and SMC controllers. Furthermore, the performed simulations highlight the ST features in terms of harmonic isolation and electrical separation between the medium- and low-voltage grid sides.