CALCULATION OF INVERTER POWER CLIPPING LOSS DUE TO PV ARRAY OVERSIZING

Abstract

The paper presents a method for calculation of Inverter power clipping loss due to PV array oversizing or high DC to AC ratio. For calculation, a PV plant installed in southern region of India having DC to AC ratio 1.4 was selected. Since a PV plant runs at full load in peak hours only (i.e. 11 am to 2 pm) when the irradiance level is ≥ 1000 W/m2 , which results in inverter power clipping (InPC) whereas at lower irradiance the produced PV power is also low which will not lead inverter power clipping. The high DC to AC ratio, increases the generation at lower irradiation but when the irradiance is high i.e. ≥ 1000 W/m2 , the inverter limits the input DC power and hence the inverter power also limited as per rated capacity of inverter. Hence the power generated by oversized PV array is lost at high irradiance and termed as Inverter power clipping loss. The significance of calculation of clipping loss is to optimize the inverter DC to AC ratio & also to estimate the guaranteed PV plant PR (performance ratio) as due to clipping loss the PV plant PR drops & it leads misinterpretation to observer as low performance of PV plant. If clipping loss is added tothe observed PR, then the actual PR will rise to meet the expected PR. Hence the paper presents the method to calculate the simulated power as per expected PV plant PR & irradiance to provide the inverter power clipping loss.