Control System Development of Medium-Voltage Modularized-Bridge-Rectifier Solid-State Transformer with RT-HIL Validation

Solid-state transformers (SSTs) are emerging as pivotal power interface devices between medium-voltage grids and low-voltage loads. This paper presents the control system development and Real-Time Hardware-in-the-Loop (RT-HIL) validation of a 250 kW, 3.3 kVAC/800 VDC modularized-bridge-rectifier (mBR) SST, which features a streamlined submodule structure comprising only one diode and one isolated DC/DC converter. A modeling approach based on the 𝑑𝑞0 − ΣΔ transformation is introduced, through which the branch current control of the mBR is fully decoupled into four independent current loops. A hierarchical control architecture—comprising central, branch, and submodule control layers—is developed and implemented within a multi-controller system. A RT-HIL platform based on multiple RT Box units is developed to facilitate distributed simulation with reduced time steps while maintaining full system functionality. RT-HIL simulations are carried out under various operating conditions, demonstrating the excellent performance of the mBR SST under the proposed control schemes.