Multilevel Power Point Tracking for Partial Power Processing Photovoltaic Converters

A Cell-Level Differential Power Processing IC for Concentrating-PV Systems With Bidirectional Hysteretic Current-Mode Control and Closed-Loop Frequency Regulation

“…This concept is known as partial or differential power processing, or Δ-conversion [13]- [26]. Various topologies have been proposed [26], ranging from buck-boost converters [13]- [15], [17], [21], [25] or switched-capacitor converters [16], [20], [24] operating between neighbouring PV modules, sub-modules or cells, to buck-boost converters or isolated flyback converters operating between sub-modules and the complete string or an individual port [19], [22], [23]. Control methodologies can be subdivided between applying voltage equalization between neighbouring (sub) modules or cells [14]- [16], [18], [20], [24], and applying MPPT to individual (sub) modules.…”

“…Control methodologies can be subdivided between applying voltage equalization between neighbouring (sub) modules or cells [14]- [16], [18], [20], [24], and applying MPPT to individual (sub) modules. In the latter case, a distinction can be made between applying central [13] or distributed control [17], [19], [21], [22], [25]. The highest-granularity examples are a hybrid inductive-capacitive converter between neighbouring groups of six c-Si cells [20] and a capacitive converter using the implicit cell diffusion capacitances to equalize cell voltages in a string [24].…”

High-density power converters for sub-module photovoltaic power management

“…In particular, a number of efforts on partial or differential power processing topologies have been reported that can achieve higher effective conversion efficiency than module-level electronics while recovering a higher fraction of the power lost to mismatch [9][10][11][12][13][14][15][16][17][18][19][20][21]. Sub-module approaches are also motivated by problems caused by the use of bypass diodes to short out weaker strings of cells.…”

“…Different approaches have been taken in this regard, mainly segmented by how the auxiliary current-flow path is constructed [21]. In ladder topologies, many submodule converters are cascaded to shuffle current up and down the series string [10][11][12][13].…”

“…Past examples of the partial power converters applied to photovoltaic systems have included both variable conversion ratio (distributed maximum power point tracking -MPPT), [20][21], and fixed conversion ratio (voltage equalization based) architectures, [11,13]. While the distributed MPPT scheme can, in theory, recover the maximum power available at the given level of control granularity, regulated or open-loop voltage equalization is nearly as effective [11][12][13][14].…”