Robustness of smart transformer based on backstepping-sliding mode controller under grid disturbances

The smart transformer (ST) is a key component for the continuously evolving smart grid applications. It is a very promising alternative to the conventional transformer owing to its numerous advantages. For instance, it allows instantaneous voltage regulation, bidirectional power control as well as the integration of renewable energy systems and electric vehicles into the distribution grid. Among the different existing ST topologies, the three-stage topology is considered as the most robust and efficient when coupled to the smart grid. In conjunction with an appropriate control strategy, it guarantees improved performance as compared to its counterparts. Several controllers were proposed for the three-stage based-ST, such as linear quadratic regulator, proportional integral, sliding mode control (SMC). However, these controllers require an exact value of ST system parameters, which is not guaranteed with the integration of renewable energies due to the abrupt changes in the atmospheric conditions. To overcome these limitations, a modified controller is proposed in this paper, namely the backstepping-sliding mode control (BS-SMC). The BS-SMC approach combines the advantages of the SMC and the BS to achieve the highest performance of the ST. The overall mathematical and numerical model of the proposed controller is provided. For a fair comparison, the SMC is also developed. Moreover, different sets of simulations were performed under normal and disturbed operating conditions. The obtained results prove the good robustness of the proposed BS-SMC and flexibility towards different electrical disturbances.