Enhancing Low Voltage Ride Through of Microinverters

Photovoltaic-based distributed generation (DG) systems are increasingly integrated into the global electrical grid. The existence of numerous DGs in the electrical grid gives rise to concerns about vulnerability, particularly with regard to voltage sag incidents. Coordination challenges between DGs may arise, potentially compromising the overall stability of the grid. Hence, it is essential for DGs to possess fault-ride-through capabilities to ensure their continuous connection to the grid. To meet this requirement, this study introduces a grid-connected microinverter utilizing a Single Leg Multimode Converter (SLMMC) and integrating an energy storage system (ESS) on its lower switch. Furthermore, the grid-interfaced system includes a low voltage ride-through (LVRT) functionality, ensuring continuous maximum power point tracking (MPPT) from the photovoltaic source. The control system utilizes a combination of a state feedback and feedforward controller (SFFC) for the AC stage and a sliding mode controller (SMC) for the DC stage. Emphasis is placed on meeting Low Voltage Ride-Through (LVRT) standards, with the controller ensuring that the Distributed Generator operates within its specified limits. The proposed control strategy, designed to handle voltage sags, is simulated and validated using MATLAB/Simulink.