Internal active power reserve management in Large scale PV Power Plants

Active Power Reserves (APRs) provided through curtailment (iAPRs) or through auxiliary storage systems (aAPR) with Large scale PV Power Plants (LPVPPs) becomes a reality in the near future with high penetration levels of Photovoltaic (PV) power into the grid. Therefore, this paper analyses the solutions for iAPR fulfilment in central inverter based - LPVPPs in terms of their layout, configuration and control architecture. During iAPR supply, the LPVPP has to operate under its Maximum Power Point (MPP), which means that the MPP algorithm has to undergo several changes. For this purpose, the paper proposes to supply iAPRs by means of a sweep function distributed over the PV inverters used in the central inverter station which has the potential to guarantee a maximum energy extraction along with a secured supply of the APR in any given meteorological condition

Scientific opinion on the tolerable upper intake level for preformed vitamin A and β-carotene

Following two requests from the European Commission, the EFSA Panel onNutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientificopinion on the revision of the tolerable upper intake level (UL) for preformed vitamin A and β-carotene. Systematic reviews of the literature were conducted forpriority adverse health effects of excess vitamin A intake, namely teratogenicity,hepatotoxicity and endpoints related to bone health. Available data did not allowto address whether β-carotene could potentiate preformed vitamin A toxicity.Teratogenicity was selected as the critical effect on which to base the UL for preformed vitamin A. The Panel proposes to retain the UL for preformed vitamin A of 3000 μg RE/day for adults. This UL applies to men and women, including women of child-bearing age, pregnant and lactating women and post-menopausal women. This value was scaled down to other population groups using allometric scaling (body weight0.75), leading to ULs between 600 μg RE/day (infants 4–11 months) and 2600 μg RE/day (adolescents 15–17 years). Based on available intake data, European populations are unlikely to exceed the UL for preformed vitamin A if consumption of liver, offal and products thereof is limited to once per month or less. Women who are planning to become pregnant or who are pregnant are advised not to consume liver products. Lung cancer risk was selected as the critical effect of excess supplemental β-carotene. The available data were not sufficient and suitable to characterise a dose–response relationship and identify a reference point; therefore, no UL could be established. There is no indication that β-carotene intake from the background diet is associated with adverse health effects. Smokers should avoid consuming food supplements containing β-carotene. The use of supplemental β-carotene by the general population should be limited to the purpose of meeting vitamin A requirements

Age- and sex-specific effects of a long-term lifestyle intervention on body weight and cardiometabolic health markers in adults with prediabetes : results from the diabetes prevention study PREVIEW

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Overview of Recent Grid Codes for PV Power Integration

The challenge to bring down the cost of produced photovoltaic (PV) power had a major impact on the PV market and in consequence the grid operators experienced higher and higher PV power penetration. The growing share of this decentralized generation plants started to affect the grid stability and Distribution System Operators (DSOs) had to keep the safety and reliability of the network under strict rules and regulations. The aim of the paper is to realize a survey of recent Grid Codes (GC) and regulations for grid connected PV systems. The focus is on grid interface requirements, power quality concerns and Anti-Islanding (AI) issues regarding PV systems connected to low voltage (LV) and medium voltage (MV) levels of the network.</p

Power ramp limitation and frequency support in large scale PVPPs without storage

Photovoltaic (PV) power generation started to become a mature technology and large scale PV Power Plants (PVPPs) operating in Maximum Power Point Tracking (MPPT) are not a solution anymore. During changes in the meteorological conditions, PVPPs output is directly influenced creating high power ramps inducing short-term voltage and frequency instabilities into the power system. System operators in countries with increased PV penetration started to become more and more conservative regarding their operation creating strict Grid Codes (GCs). As a proven fact European Network of Transmission System Operators for Electricity (ENTSO-E) pushed the limit one step forward involving PVPPs to contribute with ancillary services even to frequency support. The goal of the paper is to present PVPPs with power ramp limitation and frequency support capabilities without involving any storage equipment. This is achieved by setting the PVPP under its MPP and ensuring a certain amount of reserve. The nature of the reserve has a dynamic character, being released during transients in irradiance and frequency. The entire components of the system are modeled in RSCAD and the performance evaluated on a Real Time Digital Simulator (RTDS).</p