Comparative analysis of differential power conversion architectures and controls for solar photovoltaics

Differential diffusion charge redistribution for photovoltaic cell-level power balancing

“…In traditional DPP topologies, where a single functional block capable of simultaneously achieving DPP and MPPT is employed and distributed at the desired level of optimization granularity, local MPPT control must control the duty ratio of individual converters such that each PV elements operates at its local maximum power point [5,6]. Although any of the existing and established MPPT algorithms can be adopted [14], having local control requires additional measurement and sensing hardware for each PV element.…”

“…Differential power processing have been implemented at different levels of integration using a variety of architectures and topologies [3][4][5][6][7]. However, these approaches typically consist of a single modular functional block capable of achieving DPP and MPPT simultaneously, hence requiring these blocks with either parallel current steering inductors or voltage balancing capacitors at the desired level of MPPT granularity.…”

“…Nevertheless, while this approach may potentially extract more power overall, it is suboptimal because any available power from the underperforming sub-string is completely forfeited. In addition, the resulting output power characteristic curve is non-convex, which further complicates the maximum power point tracking (MPPT) algorithm [3,5].…”

“…The main disadvantage of cascaded architectures is the necessity to process the full power from each PV element, resulting in high insertion loss. The differential power processing schemes address the insertion loss problem by placing converters in parallel to only process the mismatch power [3][4][5][6][7]. However, all these approaches are subject to the high costs of intermediate energy storage components, such as discrete inductors and capacitors.…”

“…A few underperforming cells can cause significant loss in energy capture in a large string because series-connected cells must carry the same current, and are therefore constrained by the lowest-performing cell. Mismatches caused by partial shading, dirt accumulation, manufacturing tolerances, and different aging characteristics can severely limit the overall power extraction from a string and the negatively impact the longterm project economics [2][3][4][5][6][7][8][9][10][11][12][13].…”