Voltage and Power Ratio Effects of Grid-Connected PV Plant´s Operation on the Performance Ratio and Total System Efficiency

This paper presents an analysis of the effect of both the power ratio (inverter maximum input power/generator peak power) and the inverter input and output operational voltages, on total performance of the grid-connected photovoltaic (PV) plant. In small residential PV applications, the power ratio is usually calculated during system design and specification stage, by determining the peak PV power from guidelines given by the inverter manufacturer, without a detailed analysis of the solar resource\´s magnitude or its characteristics at the site of the application. On the other hand, the inverter input CD voltage, determined by the electrical configuration of the PV array. In operation, this voltage varies in relation to the irradiation and temperature of the PV modules. Likewise, the stability of the inverter output AC voltage (voltage from the grid at the point of connection) depends directly on "the strength" of the grid to which the PV plant is connected. This paper presents comparisons between behavior indices, calculated from measurements obtained at a PV plant in operation and adequately monitored under slightly different conditions