Enhancing micro-inverter energy capture with sub-module differential power processing

Differential power processing (DPP) is a power electronics system architecture that configures DC-DC converters in parallel with the PV string to improve its power yield. The parallel nature of the DPP architecture brings a number of benefits such as low converter power rating and low power losses, all of which make DPP especially suitable for sub-module level maximum power point tracking (MPPT). Meanwhile, micro-inverters typically perform only module level MPPT and do not address power losses due to uncompensated sub-module mis-match. In this paper, we introduce DPP converters into a micro-inverter system to improve its energy capture by recovering power losses due to sub-module mismatch. We present a small-footprint DPP converter design together with a control scheme such that the DPP converters can work with commercial micro-inverters and can be seamlessly integrated into the existing micro-inverter design. To demonstrate the effectiveness of the proposed solution, a hardware prototype was built and tested with an off-the-shelf commercial micro-inverter to prove the concept. The improvement in energy capture with DPP converters was experimentally verified.