Maximum Power Point Measurement for a String PV Inverter Using Short-Circuiting Method

The maximum power point tracking methodologies are widely used in photovoltaic (PV) systems, with perturb and observe algorithms representing the conventional approach. While perturb and observe techniques demonstrate sufficient efficacy in small-scale PV installations, their performance degrades under partial shading conditions due to an inability to accurately identify the global maximum power point (MPP). This paper proposes an advanced MPP strategy designed for string PV inverters incorporating multiple input-side boost DC-DC converters. The core innovation involves implementing a controlled short-circuiting operation through the DC-DC converter, followed by deactivation of the converter to enable uncontrolled charging of the input capacitor used for MPP identification. This sequence facilitates real-time acquisition of the PV array's instantaneous current-voltage characteristics, thereby enabling precise computation of the global MPP even under non-uniform irradiance conditions caused by partial shading. The transient analysis of capacitor charging dynamics permits rapid convergence to the optimal operating point, achieving MPP identification within a sub-20 millisecond timeframe while maintaining minimal disruption to power output during the measurement phase. This methodology effectively addresses the multi-peak power curve challenge inherent in partially shaded PV systems, demonstrating superior performance compared to conventional MPP approaches in complex illumination scenarios.