Cross harmonic generation by grid-connected high power inverters take place due to the asymmetry of inverter controllers in the presence of background harmonics in the grid. Although cross harmonic generation is often neglected in harmonic studies, the investigations reported in this paper show that the grid current magnitudes at cross harmonic frequencies can become relatively significant in some situations and hence cannot be ignored in harmonic compliance studies. This is demonstrated using example studies employing a single grid connected inverter model and a large scale three-phase solar farm model. Furthermore, an inverter harmonic model is proposed that can be used to determine the harmonic currents injected by an inverter at both the background harmonic frequency in the grid and at the cross harmonic frequency. The proposed model is validated using EMT simulation results.