Novel time‐domain average model for harmonic current prediction in photovoltaic and wind power units

Abstract

Computer models designed to assess harmonic levels created by renewable energy sources (RESs) need to reproduce the converter operation effect. However, only a few simplified time-domain models have been developed to predict harmonics while reducing simulation time, which is one of the main limitations of detailed models. This paper presents a novel time-domain model, called the harmonic average model (HM), to estimate harmonic currents generated by inverters. The superposition principle is applied to include dead time and switching effects in the average model. In addition, the snubber effect is considered by introducing snubber circuits in the HM. Time-domain simulations of a type-IV wind turbine are executed with existing models and then with the HM to evaluate the proposed model. Field measurements in a wind power plant and in a photovoltaic plant are used to validate the HM under different power injection scenarios. The results indicate that the HM follows reference currents while accurately estimating the harmonic spectra. Further, the HM is relatively simple to deploy and reduces computation time. A comparison between the HM results and field measurements suggests that the simulated spectra are an adequate approximation of the measured spectra. These results confirm that the HM can be used by transmission system operators to support the prediction of harmonic currents generated by inverters and to estimate the impact of RESs on voltage quality.