A Feedback Based Hybrid Islanding Detection Method and Voltage Ride-Through of One Cycle Controlled PV Inverter

One cycle control (OCC) based single-phase grid connected inverters are becoming popular for photovoltaic (PV) distributed generator (DG) units, because of its simple structure, cost-effectiveness and phase-locked-loop free implementation. The grid connected DG unit should have a robust islanding detection mechanism incorporated into it. This paper proposes a novel hybrid islanding detection method (IDM), which is suitable for OCC based DG systems. The nature of the OCC based inverter, which drives the VPCC away from the normal operating voltage during an islanding event is utilized to incorporate a feedback based IDM. However, when the difference between the inverter output power and the load power is near to zero, this IDM may fail to detect the condition. To overcome this drawback, a hybrid IDM, which combines the feedback effect and injection of real power disturbance, is proposed. The proposed method, unlike other active methods, injects disturbance into the grid only when an islanding condition is suspected. The induced change in power delivered by the inverter is only for a small duration of time, and the inverter goes back to the normal operation under non-islanded condition. A simple voltage ride-through which meets the recent standards for grid integration is integrated with the proposed IDM. Simulation studies are performed to verify the effectiveness of the proposed IDM.