Closed-loop string current control for string optimizer circuits-based PV system to enhance extracted PV power during partial shading conditions

Abstract

Central and string inverters are the most common technologies in PV integrated systems. The central inverter technology is simple and cheap, but its generated power is greatly reduced during Partial Shading Condition (PSC). In string inverter technology, higher power can be extracted during PSC, but multi-inverters are needed. To keep the system simple and cheap, a cost-effective solution,namely, String Optimizers Circuits (SOCs)-based PV system has been recently proposed, where central converter is employed along with SOCs (SOC for each string). The SOC is responsible for controlling its string current to ensure operating at the string GMP. In this paper, a closed-loop string current controller is presented to enhance the performance of the SOCs-based PV system. To test the effectiveness of the proposed controller, the system is simulated under different PSCs. The simulation results of the open-loop and proposed closed-loop approaches have been compared to show the effectiveness of the proposed control approach, where it provides a significant improvement in tracking accuracy under different PSCs. Circuit analysis and component design of the SOC-based PV system are highlighted. Finally, an assessment of the SOC-based PV system compared to other existing technologies is presented to show the effectiveness of the SOC-based system.

Keywords

• Central inverter
• MPPT techniques
• Scanning based-GMPPT
• String optimizer circuit