A novel switched-capacitor topology for submodule level maximum power point tracking under partial shading and mismatch conditions

摘要

Partial shading and mismatching conditions among the series connected modules/sub-modules/cells suffers from non-convex P-V or P-I characteristic curves with multiple local maxima and decreased peak power for whole string/module including by-pass diodes. This limits the power extraction from whole string/module. Energy transfer or `charge redistribution' between the sub-modules brings all sub-modules to the same operating point and this collective operation produces a convex P-V or P-I curves which have increased peak power for series connected sub-modules/cells. Then a conventional maximum power point tracking algorithm can be operated to find this maximum. A number of power electronics topologies are proposed to remove multiple local maximum points and to obtain convex P-V or P-I curves with increased peak power while ensuring that a net power gain is positive. The proposed topology benefits from switched-capacitor (SC) converters concept in a different manner and actually is an application of [1]-[3] at submodule level with some novelties; stopping the switching, string level extension. Two sub-modules share one switched capacitor converter and this allows less power electronics component usage which is nearly half of the converter number used in the literature. This advantage leads to reduced power electronics losses, cost and volume of the converter circuits. The insertion loss of the topology under uniform irradiation is calculated as 0.51% for certain values of capacitance and switching frequency. The proposed topology is simulated in PSpice environment. The simulation results confirm the loss analysis given in section II and prove that it is able to extract all the power produced by the partially shaded string and transfer to the load side.