Differential power processing architecture to increase energy harvesting of photovoltaic systems under permanent mismatch

Abstract

Differential power processing (DPP) architectures are a prominent solution for mitigating undesirable issues caused by mismatch that often occurs in photovoltaic (PV) strings. In this scenario, the association of DPP converters in parallel with PV strings is a common approach for enhancing energy harvesting. However, most topologies presented so far focus on temporary mismatch caused by partial shading conditions only, with little attention given to permanent mismatch due to the connection of modules with distinct ratings. Given the above, this article presents a novel DPP topology capable of handling both temporary and permanent mismatch in PV strings. Important advantages include lower component count; reduced voltage stresses on the active switches; operation under zero-current switching (ZCS) condition, with a direct impact on the converter efficiency; and greater design flexibility in terms of a modular solution that can be implemented at the PV module level. Experimental tests on a string composed of six modules are presented and the results are thoroughly discussed to validate the theoretical assumptions. It is effectively demonstrated that the architecture allows for increasing the power extracted from the string under two severe operating conditions.