Firmware-communicating remote terminal unit architecture for integrated photovoltaic inverter monitoring and control via I–V scanning

While modern photovoltaic (PV) inverters offer high reliability, their control intelligence is often constrained by locked firmware and conventional Perturb and Observe (P&O) algorithms. These standard methods frequently fail to account for partial shading, which creates multiple power peaks and limits energy harvesting. Although commercial inverters possess I–V scanning capabilities, they typically remain underutilized for real-time optimization because they require external triggering. This work proposes a cloud-connected, Remote Terminal Unit (RTU)-based supervisory control framework that transforms the RTU from a passive monitor into an active Maximum Power Point Tracking (MPPT) controller. The RTU acquires real-time PV voltage and PV current measurements via Modbus over RS-485 and offloads the primary computational burden from the inverter. Utilizing a TI-based controller, the RTU executes a high-level MPPT strategy and dynamically triggers the inverter’s 64-point I–V scan to reconstruct P–V characteristics. Crucially, the RTU computes the optimal operating point and sends the specific MPP reference back to the main DC-DC converter. This bidirectional communication allows the RTU to override the embedded MPPT logic without modifying the inverter’s proprietary firmware. Experimental results across multiple shading scenarios demonstrate significant improvements, achieving a tracking accuracy exceeding 99.85% and reducing tracking error below 0.15%. Compared to conventional P&O (65%–91% accuracy), power harvesting improved by up to 52.7% under severe shading. With communication latency maintained within 1–2 ms, the system ensures high stability and suppressed oscillations even during rapid irradiance transitions. Ultimately, this architecture provides a scalable, firmware-independent pathway to integrate external intelligence into commercial PV systems, ensuring superior energy harvesting in complex operating conditions.