Measurements of conducted and radiated emissions from a solar installation

In this report, results from measurements performed 7-9 June 2023 on a solar plant are presented. The solar plant was the first part of a larger installation. The installation consisted of two inverters with 20 strings of solar panels, with total max production of 100 kW. The installation was not equipped with optimizers placed at each panel, which earlier have been seen to contribute to interference problems in nearby radio systems. Measurements of both conducted and radiated emissions were made. Conducted emissions were measured for frequencies 9 kHz-200 MHz and radiated emissions for 9 kHz-1 GHz. In addition, radiated emission were measured in two frequency bands above 1 GHz used by Global Navigation Satellite Systems (GNSS). Measurements were performed with the inverters both on and off. In the measurements of conducted emission, narrowband signals were present with a distance of 16 kHz in the whole frequency band below 1 MHz, probably originating from the inverters. The same signal components were also present in the measurements of radiated emissions for the same frequency band. The solar plant caused emission levels over the measured background, for parts of the frequency bands below approximately 700 MHz at a measurement distance of 3 meters. At 10 meters measurement distance, the emissions were clearly visible for frequencies below 1 MHz and probably present at some higher frequencies, e.g. 80-120 MHz. For frequencies below 1 MHz, the highest levels were measured during peak power production. For higher frequencies, this correlation between measured level and produced power was not as clear. In conclusion, the measurements of radiated emission showed levels over the background mainly for a measurement distance of 3 meters.