Implementation of a Global Characteristic Scan Mechanism Integrated with the Perturb & Observe MPPT Algorithm under Partial Shading Conditions

Maximum power point tracking (MPPT) is considered a high priority feature for grid-tied solar inverter systems. Various MPPT algorithms are able to identify a local maximum power point (LMPP) on the P-V curve of a photovoltaic (PV) panel. Nonetheless, they often stop scanning the characteristic as soon as they detect the first available maximum. This would be problematic in situations where the characteristic possesses several maxima due to partial shading. Under such conditions, the employed MPP tracker needs to scan the $\mathrm{P}-\mathrm{V}$ curve to locate the global maximum power point (GMPP) and ensure the system operates at that point. However, it is not recommended for MPPT algorithms to scan the entire $P-V$ curve owing to efficiency and dissipation issues, unless absolutely necessary. Thus, it is crucial to provide a strategy that can identify the region containing the GMPP, and then let the LMPP tracker locate the exact GMPP. This paper investigates a proper global characteristic scan mechanism (GCSM) that incorporates the perturb & observe (P&O) algorithm to accurately identify the GMPP. The proposed algorithm is applied on a single-phase grid-tied solar inverter system operating at 20 kHz under varying input power conditions. Eventually, the experimental results are presented to confirm the appropriate performance of the system.