When multiple DC fields with non-uniform characteristics are connected in parallel to a common input, PlantPredict calculates the combined DC output using a weighted voltage averaging approach. Each DC field may have different I-V characteristics due to variations in module type, irradiance, temperature, shading, among other factors. Since parallel-connected DC fields share a common operating voltage, the algorithm assesses this shared voltage, recalculates the current contribution from each DC field at that voltage, and sums the currents to obtain total inverter input current and power.
The voltage (Vmp,i) for each DC field is calculated independently based on its specific operating conditions. When multiple DC fields are connected in parallel to a common inverter input, a weighted average determines the shared operating voltage:VDC=∑iNp,i⋅nrep,i∑iNp,i⋅nrep,i⋅Vmp,iThe weighting factor (Np,i⋅nrep,i) reflects the relative current contribution capacity of each DC field. The aggregated open circuit voltage is calculated using the same weighting approach:VDC,oc=∑iNp,i⋅nrep,i∑iNp,i⋅nrep,i⋅Voc,i
The common operating voltage is assigned to each DC field i connected to the inverter:Vi=VDCThis ensures all parallel-connected DC fields operate at the same voltage, as required by Kirchhoff’s voltage law for parallel circuits.
At the common operating voltage, the current from each DC field is recalculated using its I-V curve. The module-level voltage is determined by dividing the common voltage by the number of modules in series:Vmod,i=Ns,iVDCThe module-level current (Imod,i) is solved from the at Vmod,i using Newton-Raphson iteration. See Single Diode Model for the diode equation formulation.The DC field current is then:Ii=Imod,i⋅Np,i
The total inverter input current is the sum of currents from all parallel DC fields, accounting for repeaters, and the DC power delivered to the inverter follows directly:IDC=i∑Ii⋅nrep,iPDC=VDC⋅IDC
