This study addresses the diminishing contribution of rotating masses in central power stations and examines how decentralised energy assets (DEAs), in particular low-voltage photovoltaic (PV) inverters, can be required to provide enhanced primary frequency support under forthcoming technical connection rules. To facilitate this, a highly dynamic German implementation of Low-Frequency sensitive mode (LFSM), the “grid-security-based primary control” (PRNB) concept that activates when global frequency deviations exceed critical thresholds is currently prepared as standard and was recently published. Under PRNB, inverters must adjust their active power output with substantially faster dynamic response and stricter static limits than those prescribed by the existing VDE-AR-N-4105 standard. The present paper investigates whether, and to what extent, these tightened PRNB requirements—published for instance in a recent FNN Document [1] can already be implemented in current market-available grid-supporting DEA in the low-voltage grid. In a two-stage experimental campaign, the inverter was first evaluated in its factory default configuration (standardised in line with VDE-AR-N-4105:2018), and subsequently re-parameterised to fulfil the PRNB criteria. Initial tests comprised step changes in grid frequency under a fixed 2 kW load, with three-phase voltage and current recorded at the inverter terminals. From these signals the instantaneous active power p(t) was calculated as the sum of the products of measured phase voltages and currents. Key dynamic performance metrics—namely the initial time delay TV and the rise time T1—were assessed in accordance with both current and projected requirements. Measured values (TV ≈ 10.3 ms, T1 up to 318 ms) comfortably undercut the existing VDE limits (TV < 2 s, T1 < 2 s) by more than an order of magnitude. Thereafter, three repeat runs under a prescribed frequency profile demonstrated that the re-parameterised inverter consistently adhered to the PRNB tolerances for power response. Regression-based fitting yielded delay‐time and time‐constant estimates, complete with 1-σ confidence intervals, confirming robust and repeatable behaviour. The findings demonstrate that contemporary PV inverters can in principle meet the more stringent PRNB requirements without degradation of performance. The proposed regulation thus appears practicable from both dynamic and static perspectives, supporting the integration of high shares of decentralised generation while maintaining grid security. These results underpin the relevance of including advanced primary frequency support obligations for low-voltage DEAs in future grid codes and highlight the importance of harmonising dynamic performance and protection settings to ensure reliable grid-oriented operation.

[1]: FNN-Hinweis: VDE FNN Hinweis „Technische Anforderungen an Netzbildende Eigenschaften inklusive der Bereitstellung von Momentanreserve“

https://www.vde.com/resource/blob/2387778/d2af154bb6d0669eaaf705dbf0594b86/vde-fnn-hinweis-netzbildende-eigenschaften-download-data.pdf