Solar power disrupts wireless communications as a result of unwanted radio waves from power conditioners — MIC requests relevant organizations take action

Solar power generation systems are rapidly becoming widespread. However, there have been a number of reported cases of these systems emitting unwanted radio waves that interfere with radio facilities. On May 14, the Ministry of Internal Affairs and Communications (MIC) asked relevant organizations to inform equipment manufacturers and other relevant parties of this issue and to consider measures to prevent it. It was stated that the phenomenon of unwanted radio waves being emitted from solar power generation systems is primarily caused by power conditioners, which are devices that convert generated electricity from direct current to alternating current for domestic uses. In addition to the direct emission of unwanted radio waves by the power conditioner, there may also be the emission of secondary unwanted radio waves due to high-frequency current flowing from the power conditioner to AC and DC lines. The MIC is aware of approximately 100 cases since 2019, including suspected cases.

For example, there was a case in which unwanted radio waves from a solar power plant approximately 770 m away caused noise in the communications of a radio station for fishery guidance, making signal reception impossible. In this case, the failure was resolved by identifying the system emitting unwanted radio waves and inserting an EMI filter. In another case, unwanted radio waves from a household solar power system approximately 150 m away caused noise in the communications of a broadcast receiving station. In this case, a high-frequency ferrite core was inserted into the DC line of the household solar power system's power conditioner, which reduced radiated noise and eliminated the effect on the broadcast receiving station. Thus, a number of cases have been reported where unwanted radio waves from solar power generation systems have caused interference to fishery radios, broadcast receiving stations, disaster prevention administrative radios of local governments, and fire and emergency digital radios.

For this reason, the MIC, via the Director of the Radio Environment Division of the Telecommunications Bureau, has made a request to the Japan Electrical Manufacturers' Association and Japan Photovoltaic Energy Association. They were asked to inform related manufacturers, housebuilders, and construction companies regarding the possibility that unwanted radio emissions from solar power generation systems could interfere with radio facilities and to consider measures for reducing the impact of such emissions on radio communications.

Cases that have been confirmed so far are not limited to large-scale solar power plants in particular. There are many cases in which some equipment making up residential solar power generation systems has caused interference to human-life-related facilities handling radios, such as disaster prevention administrative radios for local governments and digital radios for firefighters and emergency services. In the event that a radio facility is interfered with severely and continuously, the interfering equipment shall be subject to an interference removal order based on Article 82, Paragraph 1 of the Radio Act as applied under Article 101 of the same law, and construction work shall be required in certain cases.

Regarding specific measures to reduce the impact on radio facilities, the MIC requested that the relevant organizations inform manufacturers and installers that the following measures need to be taken: use equipment that is expected to generate less unwanted emissions, such as equipment certified as compliant with the CISPR11 Version 6.2 standard; implement measures to reduce the impact on radio communications such as shielding power lines; or if a radio facility is impaired, remove impairments for instance by inserting noise filters. Under these circumstances, the Agency for Natural Resources and Energy's "Guidelines for Business Plan Formulation (Photovoltaic Power Generation)" has stated that efforts should be made to implement measures against electromagnetic waves and to give consideration to the surrounding environment.