Direct duty ratio controlled MPPT algorithm for boost converter in continuous and discontinuous modes of operation

Demand of increased lifetime, compact size and reduced cost of PV systems has led to the incorporation of LCL filters in the boost converter of a grid connected PV system. Additional filtering offered at the input by LCL filter reduces the inductance of boost converter. This calls for an algorithm which can track the maximum power in both discontinuous (DCM) and continuous conduction modes (CCM) of boost converter operation accurately. Direct duty ratio based perturb and observe algorithm for MPPT has been implemented in real time using VHDL based FPGA. The sensitivity of the algorithm to DCM and CCM operation of converter is analysed. It is shown that the duty ratio increment used in the MPPT algorithm should be evaluated based on the sensitivity factor. The direct duty ratio based approach is found to work well with both modes of operation, even with mode transitions.