D‐Q frame predictive current control methods for inverter stage of solid state transformer

Abstract

Solid state transformer (SST) is regarded as the most emerging technologies of energy internet. The inverter stage of SST supplies sinusoidal voltage to the home users. This study proposes model predictive current control (MPCC) of the inverter stage of SST. It is much easier to perform analysis and design controllers in DQ frame for the inverter stage of SST because all time-varying state variables of the inverter stage become DC time-invariant. Without integral action, the conventional MPCC contains steady-state errors in both d-axis and q-axis currents, hence degrading the closed-loop performance. The integral MPCC (IMPPC) is therefore proposed to eliminate the steady-state errors of the current control system and improve its closed-loop performance. Furthermore, the improved IMPCC is less sensitive to system parameter variations when compared with the conventional MPCC. Simulation and experimental results are utilised to show the successful design and implementation of the conventional MPCC and improved IMPCC. The experimental results reveal that the improved IMPCC has the benefit of fast dynamic performance, zero steady-state errors and insensitive to system parameter variations.