The presently observed rapid increase in photovoltaic (PV) micro-installation connections to low-voltage networks, resulting from numerous financial support programmes, European Union (EU) energy policy and growing social awareness of environmental and economic issues, raise the question if PV inverters widely available in EU market fulfil the numerous technical requirements specified in European and Polish regulations. The paper presents the results of an experimental study carried out on three PV Inverters widely available in the EU in accordance with the EU network code NC RfG, standard EN 50549-1:2019 and internal Polish distribution system operators’ (DSOs’) regulations, governing PV inverter cooperation with the low-voltage distribution network. The laboratory test stand scheme and its description are presented. In each test, at least one of the inverters encountered issues, either with the operation in required frequency ranges (one PV inverter), activating reactive power control modes (all three PV inverters), maintaining required power generation gradient after tripping (one PV inverter) or under-voltage ride through immunity (one PV inverter). The obtained results have shown that all tested PV inverters did not meet requirements that are the key to maintaining reliable and safe operation of transmission and distribution electrical networks.

The paper presents the results of an experimental study of 26 brand new photovoltaic (PV) inverters widely available for sale on the EU market; the study was conducted in 2021 by researchers at the AGH University of Science and Technology and Tauron Dystrybucja (Polish DSO). The purpose of the study was to compare and assess PV inverter performances in terms of their DC/AC conversion efficiencies, MPPT efficiencies, and harmonic current emissions. To examine the PV inverters, a laboratory test stand was prepared according to the standard EN 50530 and the technical report IEC/TR 61000-3-15. It was composed of a photovoltaic array simulator, a programmable regenerative AC voltage source, and a power analyzer. Each PV inverter was tested in various operating states determined by the DC voltage levels and the volume of active power generation. The results allowed for a benchmark assessment of PV inverters available on the market. The results showed how various energy efficiency indicators of individual PV inverters changed depending on their operating points. The results also revealed that, based on the performed harmonic emission tests, individual harmonics were within the normative requirements; however, in the case of several PV inverters, attention was drawn to the presence of relatively high switching frequency-related components exceeding permissible levels.

With the rapid increase in photovoltaic (PV) micro-installations in Europe, ensuring the stability and safety of the power grid has become a critical challenge. A key aspect in this context is the reliable detection of unintentional islanding by distributed energy resources. This paper presents the results of metrological tests on seven commercially available three-phase and single-phase PV inverters, conducted in accordance with the requirements of the EN 50549-1 and EN 62116 standards. A dedicated test setup was developed to enable measurements following standardized procedures. The tests assessed both the response time and the effectiveness of islanding detection mechanisms under various fault scenarios, including simulations of autonomous operation of multiple inverters. The main findings indicate that while all inverters with active islanding protection successfully detected islanding within the mandated 2-s limit, their individual response times varied significantly. Parallel operation further influenced this behavior: when one inverter operated with its islanding protection intentionally disabled, the remaining units exhibited notably increased detection times, though still within regulatory thresholds. Moreover, the inverter with disabled protection was capable of sustaining stable islanded operation indefinitely under balanced load conditions. Repeated multi-inverter tests also revealed significant variability in detection time within the same scenario, demonstrating that detection dynamics are sensitive to subtle changes in operating conditions. These findings highlight important limitations of existing certification procedures, which focus primarily on single-inverter testing. Real-world interactions between simultaneously operating inverters can substantially affect detection performance. The results therefore support the need to revise and extend test standards to include controlled multi-inverter parallel-operation conditions, ensuring the safe integration of prosumer PV systems into distribution networks.

This paper presents the results of photovoltaic inverters tests in terms of fulfillment of the technical requirements specified in European and Polish regulations governing the cooperation of micro-installations with the power distribution network. The examples of tested devices showed that the current formula of connection procedure of photovoltaic micro-installations allows the connection of photovoltaic inverters that do not meet the requirements of network code, standards and instructions for the operation and exploitation of distribution networks. These requirements are the key to maintain the correct and reliable operation of electrical networks.