OPERATION OF LONG SERIES-CONNECTED SILICON-BASED PHOTOVOLTAIC MODULE STRING AND PARALLEL-CONNECTED SHORT STRINGS UNDER PARTIAL SHADING CONDITIONS

摘要

Photovoltaic (PV) power generators can be built by connecting PV modules in series and in parallel.The chosen configuration of the generator affects its operation and, especially, under partial shading conditions it cancause substantial mismatch losses. These losses are caused by individual PV modules, which are not operating at theirmaximum power points (MPPs) even if the generator would operate in its own MPP. We have studied mismatchlosses comprehensively in this paper in three commonly used generator configurations under different partial shadingconditions by using Matlab Simulink simulation model. The generator configurations are a long string of 18 seriesconnectedPV modules and three parallel-connected PV strings of six series-connected modules in cases when theyhave the same operating voltage and when they operate as separate strings. Furthermore, the effects of mismatchlosses were studied using three representative scenarios for partial shading conditions. The results show thatseparately operated parallel-connected short strings have the lowest mismatch losses under partial shading conditions.Long strings of series-connected PV modules and parallel connections of PV strings in PV power generators cancause considerably high mismatch losses under partial shading conditions. This should be taken carefully intoaccount when designing PV power generators.