Multi-Variable Perturb and Observe Algorithm for Grid-Tied PV Systems With Joint Central and Distributed MPPT Configuration

This article proposes a new control algorithm that improves the dynamic performance in distributed maximum power point tracking systems. Systems with these architectures allow to increase the photovoltaic power harvested in case of partial shading and irradiance mismatch. The classical approach adopts distributed DC/DC power electronics and control without any centralized action, which makes difficult to know whether the system is working on its optimal operating point or not. The new control algorithm presented in this paper exploits the benefits of the vectorial multi-variable perturb & observe logic and acts on the control sequence under varying irradiance conditions, reducing voltage stresses at the DC/DC converters output terminals. In addition, the matching with the DC-bus voltage control is discussed, providing a centralized control to the overall system, a fact barely addressed in literature. Simulation results and experimental measurements validate the proposed approach showing improved dynamic performance and system stability.