Direct Model Predictive Control of a Single-Phase Grid-Connected Siwakoti-H Inverter

The Siwakoti-H flying-capacitor inverter (sFCI) is a recent member of the family of transformerless inverters. Due to its minimal design, it presents a favorable alternative to conventional transformerless topologies. One of the major challenges in the control of the sFCI is to maintain the flying capacitor voltage within prescribed limits. To address this issue, a direct model predictive control (MPC) scheme is proposed for a single phase grid-connected sFCI. A discrete-time switched nonlinear model of the converter is derived, which captures the dynamics of the flying capacitor and the LCL filter. The nonlinear model enables the accurate prediction of the system behavior over the whole operating range. The proposed MPC strategy is tasked to work in two different modes, i.e., grid-disconnected mode and grid-connected mode, with specific control objectives. The presented results demonstrate the flying capacitor voltage control in grid-disconnected mode, and also illustrate the steady-state and dynamic performance of the controller in grid-connected mode.