Audio Frequency Injection Control (AFIC) signals, are voltage waveforms that are superimposed onto the supply voltage at distribution level in order to switch loads such as off-peak hot water systems or street lights. There is anecdotal evidence that PV inverters are impacting AFIC signal magnitudes. With the continued rise in popularity of rooftop PV, and the current lack of knowledge of how significant the impact may be, work has been undertaken to understand the impact of PV inverters on AFIC signals. This impact has been assessed using three methods;

- Field measurements

- Laboratory testing

- Computer simulation

The field measurements were performed on a large solar installation at the University of Wollongong. An experimental program was designed which aimed to determine the impact of the PV inverters on AFIC magnitudes. Significant signal attenuation was observed throughout this process and led to further measurements being required in laboratory conditions.

Laboratory testing was then performed on 4 residential sized inverters. A waveform generator was used to simulate a 230 V waveform superimposed with 5% 15^th harmonic. The impact of the tested inverters on AFIC magnitudes varied across the four different inverters with the outcome suggesting that the type of grid-connection filter used significantly alters the impact that the inverter has on the AFIC signal magnitude.

Computer modelling was able to replicate the results found during field and laboratory testing by representing the inverter as an ideal current source with a passive front-end filter. Further simulation investigated the impact that different filter types may have on the AFIC signal magnitudes.

The result of the work confirms that common PV inverters can have an impact on AFIC signals and that the impact greatly depends on the type of front-end filtering that is employed. Further work is required to determine the impact in real-world networks.