Frequency evaluation of the Nordic power system using PMU measurements

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. © 2017, The Institution of Engineering and Technology.

[1]  J.A. Ferreira,et al.  Wind turbines emulating inertia and supporting primary frequency control , 2006, IEEE Transactions on Power Systems.

[2]  Ola Carlson,et al.  Frequency support by wind farms in islanded power systems with high wind power penetration , 2013, 2013 IEEE Grenoble Conference.

[3]  Shun-Hsien Huang,et al.  System Inertial Frequency Response estimation and impact of renewable resources in ERCOT interconnection , 2011, 2011 IEEE Power and Energy Society General Meeting.

[4]  Pengwei Du.  Using disturbance data to monitor primary frequency response for power system interconnections , 2014, 2014 IEEE PES General Meeting | Conference & Exposition.

[5]  O. Samuelsson,et al.  Frequency deviations and generation scheduling in the nordic system , 2011, 2011 IEEE Trondheim PowerTech.

[6]  Zhao Xu,et al.  Evaluating frequency quality of Nordic system using PMU data , 2008, 2008 IEEE Power and Energy Society General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century.

[7]  B. Francois,et al.  Dynamic Frequency Control Support by Energy Storage to Reduce the Impact of Wind and Solar Generation on Isolated Power System's Inertia , 2012, IEEE Transactions on Sustainable Energy.

[8]  Zhian Zhong,et al.  Power Systems Frequency Dynamic Monitoring System Design and Applications , 2005 .

[9]  Nicholas Jenkins,et al.  Frequency support from doubly fed induction generator wind turbines , 2007 .

[10]  N. Jenkins,et al.  Comparison of the response of doubly fed and fixed-speed induction generator wind turbines to changes in network frequency , 2004, IEEE Transactions on Energy Conversion.

[11]  Yilu Liu,et al.  Global behaviour of power system frequency in korean power system for the application of frequency monitoring network , 2008 .

[12]  T. Thiringer,et al.  Temporary Primary Frequency Control Support by Variable Speed Wind Turbines— Potential and Applications , 2008, IEEE Transactions on Power Systems.

[13]  B. J. Kirby,et al.  Frequency Control Concerns In The North American Electric Power System , 2003 .

[14]  D.P. Chassin,et al.  Estimation of WECC system inertia using observed frequency transients , 2004, IEEE Transactions on Power Systems.