Possible EMC problems with DC optimisers

9/13/19, 2:03 PM -

In Switzerland, some PV systems have interfered with the frequency bands of amateur radio. These systems were fitted with DC optimisers. Now the plants have to be extensively rebuilt or shut down. We would like to know: Have you experienced any issues?

Possible EMC problems with DC optimisers
Keep in mind: The vast majority of DC optimisers work perfectly normally.

Normally, photovoltaic systems do not interfere with the protected frequency ranges of, for example, amateur radio (150 kilohertz to 30 megahertz) or emergency services. However, in some systems with DC optimisers, the Swiss Federal Office of Communications (BAKOM) has detected interferences that in some cases significantly exceeded the permissible level for Electromagnetic compatibility (EMC).

Since these frequency ranges are protected, the operators were asked to convert the solar systems to comply with EMC, that is to say, to upgrade these at great expense. Otherwise, the plants would have to be decommissioned.

We kindly ask for your cooperation

To explore the scale of the problem – and because there have also been unsubstantiated rumours that similar issues have come up in the UK and the US – we are asking you, dear readers, for your help. There may be specific effects involved with DC optimisers that are not yet properly understood and that are not adequately covered by the standards and FCC tests for such devices.

If several optimisers are interconnected on the roof, the clock frequencies of the electronics in the devices and the communication with the inverters may generate certain fields of interference, which could also be reinforced by the DC strings.

We would like to hear from you, if you have experienced or are experiencing similar issues with DC optimisers. Please get in touch with us – and we will be happy to treat your information confidentially.

Please contact Heiko Schwarzburger, editor-in-chief of photovoltaik/pv Europe. (e-mail: schwarzburger@photovoltaik.eu, phone: +49-30/24536549) (HS/mfo)