Flexible power point tracking (FPPT) control algorithms have been introduced in the literature to provide frequency support in low-inertia grid-connected photovoltaic (PV) systems. This is achieved by regulating the PV output power to a power reference obtained from the energy management system. Partial shading of PV arrays is a frequent phenomena that needs to be investigated for FPPT operation of PV systems. This paper proposes a simple and improved secant-based global FPPT algorithm that tracks the power reference during partial shading conditions. Guaranteed and fast convergence with flexibility to operate on both sides of the global maximum power point are the main contributions of the proposed algorithm. Experimental validation is carried out to demonstrate the efficacy of the proposed algorithm. IEEE