Dynamic Modeling and Model Predictive Control of Hybrid Solid-State Transformers

Solid-state transformer (SST) has been widely used in the distribution system as an emerging technology, and it is a potential solution to displace the conventional line-frequency transformer (LFT) at the distribution substations. The modern power system is comprised of increasing penetration of distributed energy resources and dynamic loads, whose operation stability, flexibility and resiliency could be guaranteed by the advanced control functionalities of SST, such as power flow control, fault current limiting, among others. However, the potential cost increase could hinder the wide deployment of SSTs. Another available solution is the hybrid SST (HSST), where the SST shares only partial power while maintains the advanced functionalities. The HSST obtains both advantages of SST and LFT. Though featuring a lower cost without jeopardizing the operational performance, HSST is still in the pre-mature stage and the corresponding dynamic model and control strategies have not been completely established and developed. In this paper, the detailed dynamic model of HSST is established first. The corresponding model predictive control (MPC) is further implemented for the HSST considering its nonlinearities and constraints. Finally, the time-domain tests in PLECS are conducted to verify the effectiveness of the developed mathematical model and proposed control method.