Evaluation of Interoperability Functions via Modbus-TCP for Photovoltaic Inverters

Control of voltage and frequency fluctuations in a power grid have been very hot topics studied due to the high-penetration of variable renewable energy sources such as wind and solar powers to the grid. In order to reduce the voltage and frequency fluctuations of the grid, the smart inverters can control voltage and frequency through several functions implemented according to international standards. This functionality is enhanced by the ability of interactively change settings through communications, so-called interoperability. The SunSpec Alliance sets a set of protocols in order to standardize the information exchanged from the inverter, so that grid operators are able to get the same information in the same way regardless of the manufacturer. This paper presents test results of SunSpec communication for Volt-VAR test, Frequency-Watt test and Volt-Watt test implemented for UL 1741 supplement A. The test is verified through a C-HIL test setup, including Volt-Watt, Volt-VAR and Frequency-Watt. Test results show satisfactory performance for interoperability of the tested functions.