RCC-MPPT algorithms for single-phase PV systems in case of multiple dc harmonics

In this paper the implementation of maximum power point tracking (MPPT) schemes by the ripple correlation control (RCC) algorithm is discussed in case of multiple ripple harmonics. As an example, a single-phase single-stage grid-connected photovoltaic (PV) system based on H-bridge inverter and level doubling network (LDN) is considered, leading to a multilevel inverter having the double of output voltage levels compared to the basic H-bridge inverter topology. The LDN is basically a half-bridge fed by a floating capacitor, with voltage self-balancing capability. In this case, additional voltage and current harmonics are introduced in the dc-bus of the H-bridge, leading to multiple PV voltage and current low-order harmonics comparing to the double fundamental frequency component in case of basic H-bridge configuration. Voltage and current harmonic components are used in RCC schemes to estimate dP/dV and to drive the PV operating point to the MPP. Different possible dP/dV estimations have been proposed in case of multiple harmonics, and a specific case with LDN has been considered. The steady-state and transient performances of the proposed RCC-MPPT schemes have been numerically tested and compared by MATLAB/Simulink.