Sine Wave Current Tracking of Grid-tied Two-stage Single-phase Inverter via Adaptive Model Predictive Control with Voltage Regulation

Two-stage inverters have been commonly applied in the distribution systems, where Total Harmonic Distortion (THD) is important for the judgement of the tacking effects. This paper focuses on the current tracking of the grid-tied two-stage inverter composed by the front buck-boost converter and the rear single-phase inverter. A cascaded Proportional-Integral (PI) Model Predictive Control (MPC) is applied for the intermediate voltage tracking of the front stage. Meanwhile, an adaptive MPC scheme is adopted for the output current tracking of the single-phase inverter stage by introducing an time-varying observer for the filter inductance and load resistance identification. By regulating the intermediate voltage, there will be a corresponding voltage which minimizes THD under the same other parameters. Hence, a reference voltage generator based on the circuit parameters, the input voltage, the reference current and grid voltage is employed for the voltage regulation to obtain lower THD. The simulation results show the effectiveness of the control scheme for the two-stage inverters applied in this paper.