An improved MPPT algorithm based on hybrid RCC scheme for single-phase PV systems

Single-stage H-bridge grid-connected inverters are considered as a simple, compact, and economic topology compared with double-stage converters. A maximum power point tracking (MPPT) control is necessary in photovoltaic (PV) generation system to extract maximum power from the PV arrays. Many MPPT techniques have been proposed and discussed in the literature. Among them, the ripple correlation control (RCC) algorithm is fast and effective, particularly suitable for single-phase configurations since it uses as perturbation the embedded oscillation of dc current and dc voltage at twice of grid frequency (e.g., 100 Hz). The main drawback of this method is the unstable behavior during sudden variation of sun irradiance, where the conventional RCC gives wrong estimation of the power derivative (dP/dV), causing wide dc voltage and dc current overshoots. To overcome this problem, a hybrid RCC-constant voltage regulator algorithm combined to a high-peformance dq grid current controller is proposed to improve the transient performance. The whole grid-connected photovoltaic generation scheme has been implemented numerically by MATLAB/Simulink, verifying steady-state and dynamic performances under different sun irradiance transients. The comparison with the corresponding behavior of a standard RCC algorithm emphasized the effectiveness of the proposed hybrid RCC controller.