High Voltage Selective Global Flexible Power Point Tracking for Photovoltaic Systems

To provide frequency support in grid-connected photovoltaic (PV) systems with low inertia, flexible power point tracking (FPPT) control algorithms have been developed in the literature. To achieve this, a power reference obtained from the energy management system is used to control the PV output power. For PV systems to operate with FPPT, the frequent phenomenon of partial shading of PV arrays must be investigated. Among the multiple operating points possible for a given power reference, the one with a high voltage level should be selected in order to minimize the current stress on the semiconductor devices and to reduce the converter thermal stress. This work proposes an improved secant method to achieve this objective, which converges to a voltage reference that is higher than the global maximum power point voltage. The performance of the proposed high voltage selective global FPPT algorithm is validated through simulations in MATLAB-Simulink and experiments conducted on a scaled-down laboratory test setup.