Time delay consequences on ramp rate control for grid-connected PV systems: A deterministic approach to grid code compliance

High-penetration photovoltaic (PV) plants introduce short-term power fluctuations that can violate grid-code ramp-rate limits and lead to penalization. Although battery energy storage systems (BESS) are widely used to enforce ramp-rate constraints, the impact of practical time delays arising from sensing, control execution, communication, converter dynamics, and battery response is typically neglected or treated heuristically in existing studies. This paper proposes a deterministic, measurement-driven framework to quantify how time delay degrades ramp-rate compliance and to prescribe delay-robust mitigation measures for different PV plant sizes and grid-code requirements. The framework is developed using one-year field measurements sampled at 5 s from the 38.5 MW Amaraleja PV plant in Portugal (including subsections from 0.55 MW to 38.5 MW), complemented by validation with datasets from Navarra, Spain, and experimental observations from a 1 MW PV–BESS facility indicating an overall delay of approximately 3 s. The results demonstrate that implementation delays can significantly increase ramp-rate non-compliance, potentially triggering curtailment penalties under strict grid-code regimes. To address this issue, two complementary solutions are proposed to achieve zero non-compliance without requiring costly hardware upgrades: (i) ramp-rate parameterization, which adjusts the internal ramp limit to account for delay effects, and (ii) a deterministic tolerance-based approach for grid-code amendment. The proposed framework provides a systematic methodology to ensure reliable ramp-rate compliance under realistic operating conditions, offering practical guidance for both plant operators and system operators.