Categorizing the Meteorological Origins of Critical Ramp Events in Collective Photovoltaic Array Output

Abstract

Photovoltaic (PV) solar power use is increasing globally. The Australian Capital Territory (ACT) has legislated a renewable energy target of 90% by 2020; to reach this target, use of distributed PV solar arrays is expected to increase. Cloud cover can cause the power output of PV installations to rapidly increase or decrease, resulting in ACT-wide collective ramp events. Accurate forecasts of when the ramp events will occur are needed for electricity providers to plan for these abrupt output changes and to ensure that electricity supplies remain stable. This paper categorizes the weather events that cause changes in the output of rooftop PV arrays in the ACT, providing a foundation for future PV output forecasting to be based on weather event identification. This paper identifies citywide collective ramp events, which occur when a 60% change in collective PV power output (with respect to the clear-sky potential) is experienced within 60 min. Such events are termed critical collective ramp events. Throughout the period between January 2012 and July 2014, 34 critical ramp events occurred. Eighteen of these events were positive collective ramp events, caused most frequently by Australian northwest cloud bands and radiation fog dissipation. Sixteen negative collective ramp events were recorded, and they were caused most frequently by the passage of cold fronts and thunderstorms. The categories developed herein will make it possible to improve short-term solar forecasting methods and to enable meteorologists to contribute to forecasting critical events.

Estimation of satellite‐derived regional photovoltaic power generation using a satellite‐estimated solar radiation data

“…Proposed estimation will be useful for power TSO and DSO (electric power companies have a role of TSO and DSO in Japan).The proposed PV power generation estimation method should be useful in the analysis of PV power generation during rapid variations of PV power generation (ie, ramp events) in order to estimate their impact on the power grid, because it provides data with a high temporal and spatial resolution.…”

“…Proposed estimation will be useful for power TSO and DSO (electric power companies have a role of TSO and DSO in Japan).The proposed PV power generation estimation method should be useful in the analysis of PV power generation during rapid variations of PV power generation (ie, ramp events) in order to estimate their impact on the power grid, [28][29][30] because it provides data with a high temporal and spatial resolution. Furthermore, the method described in this study may have higher potential for various energy management scenarios in the field of safe energy control (eg, electric power management, energy storage management, electrical transmission, and measures for PV curtailment.…”

Solar Irradiance Forecasts by Mesoscale Numerical Weather Prediction Models with Different Horizontal Resolutions

“…Cumulus clouds (i.e., thunderstorms) often tend to develop rapidly and cause swift decrease of GHI values (i.e., ramp events, see Section 5). Wellby and Engerer, [13]) identified weather types (thunderstorm, cold front, cloud band etc.) for city-scale negative ramp events in Australia.…”

“…Ramp events frequently cause rapid increases and/or decreases of PV power generation. Wellby and Engerer [13] categorize city-scale (defined as a region size of approximately 30 km) ramp events according to meso-scale and synoptic-scale meteorological phenomena (e.g., cold fronts, thunderstorms, cloud bands). If the NWP can accurately predict these meteorological phenomena, then the ramp events can also be predicted.…”

Regional photovoltaic power fluctuations within frequency regulation control time frames: A study with high‐resolution data

“…Regarding the high‐frequency components of solar irradiance fluctuations and how they generate ramps of PV power, Lave et al analysed clearness index data with 1 second of resolution in 6 locations near each other in San Diego, California . The authors performed a wavelet decomposition to analyse the fluctuations and found a good level of agreement between their results and the model developed by Hoff et al In addition, Wellby and Engerer categorised cloud phenomena and weather phenomena associated with ramps of PV power in the Australian Capital Territory . They showed that the most positive ramps were caused by cloud bands and fog dissipation and that negative ramps can be related with the passage of cold fronts in the area studied.…”