A Control Strategy for Dual-Input Neutral-Point-Clamped Inverter-Based Grid-Connected Photovoltaic System

This article presents a control strategy for a dual-input neutral-point-clamped (NPC) inverter-based grid-connected photovoltaic (PV) system to asymmetrically control the PV arrays without incorporating any additional external circuit. This is achieved by employing an analytically developed linearization block, which helps in generating the required neutral point (NP) current to counter for the difference in the PV currents. The analysis also provides the maximum NP current compensation limits of the NPC inverter. If the required NP current reference is less than the maximum limit, both PV arrays operate at their maximum power points. However, if the required current exceeds the limit, one of the PV arrays operates at its maximum power point, while the output power of the other PV array is reduced to satisfy the NP current limit. Experimental tests are conducted on a laboratory prototype to validate the performance of the proposed control strategy.