Beyond the curves: Modeling the electrical efficiency of photovoltaic inverters

It has been noted that the models typically used to represent inverters in simulation and design tools at the present are inadequate because they do not capture the variations in electrical efficiency over the full range of operating conditions. Data to develop more detailed models have been scarce in the past, but are now increasingly available from multiple sources, therefore it is time to rectify the situation. This paper examines efficiency measurements for a wide range of different inverter products at multiple power levels and input voltages. A model is developed that expresses efficiency as a function of both power and voltage, and it is demonstrated that this model can approximate the efficiency with an appropriate level of accuracy using a small number of parameters. This combination of accuracy and simplicity should facilitate implementation in software and dissemination of model parameters.