Open AccessFrequency evaluation of the Nordic power system using PMU measurements
Author(s) -
Persson Mattias,
Chen Peiyuan
Publication year - 2017
Publication title -
iet generation, transmission and distribution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 110
eISSN - 1751-8695
pISSN - 1751-8687
DOI - 10.1049/iet-gtd.2017.0095
Subject(s) - frequency deviation , phasor , electric power system , units of measurement , automatic frequency control , nadir , wind power , environmental science , power (physics) , computer science , control theory (sociology) , statistics , mathematics , telecommunications , engineering , electrical engineering , control (management) , physics , quantum mechanics , satellite , artificial intelligence , aerospace engineering
This study investigates the frequency behaviour in the Nordic power system (NPS) utilising phasor measurement units (PMUs) from different locations in the system. Different metrics are selected or proposed to quantify the system frequency response in case of major disturbances and of daily normal operations. Based on the collected PMU data, there are on average 17.5 major, generator disconnection related, disturbances per year. The maximum absolute rate of change of frequency exceeds 0.1 Hz/s for 20% of these disturbances. The average frequency nadir falls to 49.7 Hz, and the average time to nadir is about 8.7 s. If wind turbines were to be requested to provide inertia support to the system, these four metrics indicate how often, how fast, for how much and for how long the wind turbines should act. Moreover, during daily normal operations, the system has in general longer duration of over‐frequency ( f > 50.1 Hz) than under‐frequency ( f < 49.9 Hz). These frequency deviations are observed to occur around the hourly clearing of the Nord Pool Spot market and, especially during the hours between 05:00 and 08:00. In order to improve the frequency quality, the Nordic system operators tested and implemented an automatic frequency restoration reserve (aFRR) in addition to the existing manual one. Based on a frequency evaluation, this aFRR is needed most during 4:45–08:15 and 22:00–23:30 o'clock in 2012 in the NPS.