A multi-string differential power processing based voltage equalizer for partial shading detection and mitigation in PV arrays

Abstract-: Partial shading deteriorates the overall performance of photovoltaic (PV) arrays by reducing the power output. Various shading mitigation strategies have been proposed in the literature with vulnerabilities of limited applications, switches, sensor counts, design, cost, and complexities. In this paper, a multi-string differential power processing (MS-DPP) based voltage equalizer is proposed for power output improvement in the PV arrays during shading. The equalizer is utilized for the series-parallel array which is equipped with a shading detection system achieved from the optimal placement of minimum sensor counts. The technique uses the concept of a switching capacitor that balances the voltage ratio between the modules of individual strings to ensure higher power generation and convex power curves during shading. The system is simulated and validated in MATLAB simulation and further verified on the OPAL-RT 4510 hardware-in-loop FPGA-based real-time platform. The technique is executed on three array sizes and compared with existing techniques under static and dynamic partial shading cases. The analysis shows that MS-DPP enhances the array power output with a conversion efficiency higher than 99 % during shading with lower system size and 98.38 % and 95.05 % reduced counts of switches and sensors than dynamic reconfigurations.