Control Algorithm for Differential Power Processing Resonant Converter Under Partial Shading and Short-Circuit Fault in Photovoltaic Systems

Partial shading on a photovoltaic string consisting of multiple panels triggers a significant reduction in energy yield. Various kinds of differential power processing (DPP) converters have been proposed to prevent the partial shading issues. However, if DPP converters unnecessarily operate under unshaded conditions, no-load losses lower the system efficiency. Meanwhile, in case of short-circuit fault of panels, DPP converters might be destroyed due to over-current. Previous works have proposed DPP resonant converters that realize inherent over-current protection capability in discontinuous conduction mode (DCM). However, the peak currents in DCM tend to be large, resulting in increased conduction losses. This paper proposes a novel control algorithm for the DPP resonant converter to detect partial shading and short-circuit faults. The DPP converter is disabled under unshaded conditions and operates in DCM under short-circuit fault conditions. Experimental results demonstrated the energy yield enhancement under shading conditions and over-current protection capability under short-circuit fault.