Simplified embedded control scheme for two-stage multistring off-grid inverter

This study proposes an embedded control for an off-grid single-phase multistring inverter with front-end DC-DC conversion stage followed by a synchronised H-bridge. In this inverter, the duty cycle of DC-DC converter is varied in the form of fully rectified sinusoidal fashion to produce a similar output voltage across the DC-link capacitor. This unidirectional voltage is converted into an AC voltage by the synchronised H-bridge. An application of this inverter topology with the proposed control scheme in micro-grid is investigated in the present study. The proposed control scheme not only possesses better steady-state performance with both linear and non-linear loads but also provides fast dynamic response during a step change in load. A digital controller based on field programmable gate array is utilised for the simultaneous generation of high-frequency switching pulses for DC-DC converter and synchronised fundamental frequency switching pulses for H-bridge. The entire system is simulated in MATLAB/Simulink® environment and its functioning is verified with linear and non-linear loads. The hardware prototype of inverter is also built in the laboratory and its performance is validated. Further, the better performance of the proposed system for supplying household appliances is ascertained in the laboratory.