Novel Control for a Buck Converter used in a DMPPT System

This paper is focused on the digital implementation of a voltage and a current loop for a buck converter used in distributed maximum power point systems (DMPPT). It presents the importance of an additional control to help the maximum power point tracking (MPPT) algorithm. The paper gives a detailed small signal analysis and describes the method for compensating the current and voltage loop, making the stability of the system independent of the operating point on the power voltage (P-V) characteristic. The paper also proposes an original Perturb and Observe (P&O) algorithm with variable step size to search a local maximum. The calculation of the step size is independent from the slope of the solar panel's P-V characteristic, making the tracking performances independent of the PV module. Simulation and experimental results are finally provided to verify the performance of the system.