A method for quantifying availability losses caused by PV inverter start-up delays in a large-scale PV power plant: A case study in Southeastern Brazil

The optimization of photovoltaic power plant (PVPP) performance is critical for maximizing financial returns. Inverter startup delays represent a significant yet often unquantified source of reduced system availability and associated energy losses. Quantifying this phenomenon remains challenging due to the lack of standardized methodologies and performance indicators. This study proposes a systematic and replicable methodology to quantify the impact of inverter startup delays based primarily on sunrise time and comparative analysis of AC power generation data. Plane-of-array (POA) irradiance measurements are used only for configuration and validation purposes. The methodology is applied to a utility-scale PVPP located in the western region of São Paulo State, Brazil. Analysis of high-resolution operational data from 2023 reveals that asynchronous inverter startup persists even under sufficient irradiance conditions, with delays of up to four hours after sunrise. The resulting energy losses are substantial: delays occurring within the first 90 min after sunrise account for more than 55% of the total annual loss. Quarterly analysis shows that the first semester (summer and fall) is responsible for 68.8% of the losses. Performance variability among the eight analyzed inverters is significant, with monthly energy losses ranging from 0.14% to 5.02% of their total generation. The aggregate annual energy loss for the PVPP is quantified at 1.88%, comparable to conventional losses such as module mismatch and system unavailability. The proposed methodology provides a practical tool for identifying availability-related performance issues and supporting targeted operational improvements in large-scale PV systems.