Evaluation of German residential solar PV inverters

This paper evaluates five different residential solar photovoltaic (SPV) inverters, designed to operate according to German standards, in different system conditions. The testing was performed in Southern California Edison´s (SCE) DER Laboratory in Westminster California. The main purpose for testing these inverters is to explore features not currently available in inverters that follow USA standards. These features include: ability to adjust ramp-up power rates, low voltage ride through, adjustment of power factor (PF) based on real power output, provide or withdraw VARs during voltage deviations, ability to adjust output real power during over-frequencies, and ability to communicate. The detailed results here will provide input to national standards being developed for advanced features. The test data can be used for model development and validation to assess grid performance with high penetration of inverters with these characteristics. For the tests the inverter frequency was adjusted from 50 to 60 hertz (Hz) to more properly simulate the electrical grid in the USA. The inverters output voltage was 230 volts line-to-ground, reflecting the typical German residential voltage configuration. The inverters could not be adjusted to split-phase 240 volts line-to-line, the typical USA residential voltage configuration.