Working Group Meeting North American SynchroPhasor Initiative June 8-9, 2010, Vancouver, British Columbia Wide area monitoring and control activities in Norway and the Nordic power system Kjetil Uhlen, NTNU Norwegian University of Science and Technology, (and SINTEF Energy Research) Norway 1
Outline The Nordic power system WAMS activities, objectives and applications Power oscillation monitoring PMU measurements On-line monitoring From WAMS to WACS.. (ongoing and future work) Concluding remarks 2
Outline The Nordic power system WAMS activities, objectives and applications Power oscillation monitoring PMU measurements On-line monitoring From WAMS to WACS.. (ongoing and future work) Concluding remarks 3
The Nordic Power system Norway (TSO Statnett): Regional control centres National control Centre - Oslo 4
Nordic system dynamic characteristics Modal Analysis: Identified and classified oscillatory modes Oscillatory Frequency Relative Damping Mode Classification Main Observability Area 0.33 Hz 5.40 % Inter-area mode Finland / Southern Norway 0.48 Hz 2.48 % Inter-area mode Sweden / Southern Norway 0.55 Hz 3.39 % Local area mode Northern Norway 0.62 Hz 6.20 % Inter-area mode Sweden / Central Norway 0.76 Hz 1.48 % Local area mode Western Norway 5
Outline The Nordic power system WAMS activities, objectives and applications Power oscillation monitoring PMU measurements On-line monitoring From WAMS to WACS.. (ongoing and future work) Concluding remarks 6
Statnett s assessment of potential benefits and applications of WAMS Workshop at Statnett in 2006 to assess promising functions and benefits In operation Operation planning For protection and fault analysis On-line functions Various displays and indicators Power oscillation monitoring, voltage instability, voltage flicker,.. Off-line functions Plotting and display functions Analysis tools Trigging functionality (for identification of events and storing data) 7
Main findings On-line information and trending of complex information is not considered as very useful. Operators do not have time to look at this information, especially not in stressed situations. Simple alarms and information quantifying presence and characteristics of power oscillations is useful. Such information is not available today. On-line calculation of high voltage flicker levels is useful in some substations. Off-line: Good tools for storing, displaying and analysing phasor data are important. Useful for many off-line analysis purposes, including forensic analyses and model validation. 8
WAMS prototype 9
Forside 10
Outline The Nordic power system WAMS activities, objectives and applications Power oscillation monitoring PMU measurements On-line monitoring From WAMS to WACS.. (ongoing and future work) Concluding remarks 11
Comparing Phasor Measurements with EMS- State Estimator - Voltage angle differences 12
Measurements from a disturbance in the Nordic grid on August 14, 2007 What system information can be obtained from the PMUmeasurements? What is the additional information compared to available SCADA-measurements? What is the additional benefit of WAMS? 13
Operating condition on August 14, 2007 Light load situation Surplus of hydro power Main power flows: West east North south Network split in Mid-Norway PMU sites 14
Power flow Røssåga-Rana 1 hour 15
Power flow Røssåga-Rana 3 min. 1 hour 16
Power flow on main transmission lines 2200 Power flow on lines monitored by PMUs 2000 Power (MW) 1800 1600 1400 1200 1000 800 600 400 200 Power flow from Hasle towards Sweden From Kristiansand towards West Denmark (HVDC) Power flow on ac lines towards Finland from Sweden Towards Fardal (from generators to the north) From Nedre Røssåga (towards Rana in the north) 0 0 20 40 60 80 100 120 140 160 180 Time (seconds) 17
PMU-monitored voltage angles 50 Relative Voltage phasor angles (Ref. Hasle) 40 30 Angle (degrees) 20 10 0 Nedre Røssåga Fardal Kristiansand -10-20 0 20 40 60 80 100 120 140 160 180 Time (seconds) 18
Power oscillation monitoring function 2200 Power flow Hasle towards Sweden 80 Amplitude of 0.5 Hz mode 2100 60 Power (MW) 2000 1900 power (MW) 40 20 1800 0 50 100 150 Time (seconds) 0 0 50 100 150 Time (seconds) 0.8 Frequency of main oscillatory mode (0.5 Hz) 40 Damping of 0.5 Hz mode 0.7 30 Frequency (Hz) 0.6 0.5 0.4 0.3 Damping (%) 20 10 0 3% alarm limit 0.2 0 50 100 150 Time (seconds) -10 0 50 100 150 Time (seconds) 19
Forside 20
Outline The Nordic power system WAMS activities, objectives and applications Power oscillation monitoring PMU measurements On-line monitoring From WAMS to WACS.. (ongoing and future work) Concluding remarks 21
When/how to utilize PMUs and WAMS for power system control? When there is a need for system wide information (more than just local information) AND high resolution dynamic information AND/OR time synchronized measurements Power oscillation damping Voltage collapse protection (based on fast detection of voltage instability problems) Frequency instability (out of step) protection Emergency control / System protection schemes How: Power system stabilisers (coordinated design) Control of SVC/FACTS and HVDC (active and reactive power control) Generator tripping / Load shedding Network splitting (breaker control) 22 22
Kvandal Wide-area POD Goals: Study the use of PMUs as measurement signals, Investigate coordinated stabilizer design, using SVCs Identify benefits and challenges with wide area measurements, compared to traditional local measurements SVC Røssåga SVC Tunnsjødal SVC Verdal SVC Viklandet SVC Sylling SVC Hasle SVC Rød SVC Kristiansand SVC 23
POD - Power Oscillation Damper Design and testing Control-loop design Wide-area and local POD controllers POD Measurement Control WA-POD Local POD Voltage angle difference: Kristiansand Røssåga Power flow: Hasle corridor (Sweden-Norway) Hasle SVC Hasle SVC 24
Time Domain Simulations Small Disturbance Large Disturbance Active power flow: Norway-Sweden: Black curve: No PSS Red curve: WAMS Single-tuned PSS: Sylling (0.33 Hz) & Rød (0.48 Hz) Blue curve: Local Single-tuned PSS: Sylling (0.33 Hz) & Rød (0.48 Hz) 25
Result and Conclusions Stabilizers with local or wide area measurements considerably improves damping of inter-area power oscillations Wide-area solution can be more robust with better performance for wider range of operating scenarios and subject to larger disturbances Remote PMU measurements enhances observability Simplifying stabilizer design Improving damping on wider range of modes Potential PMU challenges: Availability and communication delays Suggested solution: dual input solution Possibility of fall-back to local signals Provides increased robustness 26
From WAMS to WACS.. 27
Wide-Area POD implementation South Norway Capacity +/-2000 MW Sweden U, I MACH 2 POD U PMU PMU PDC Data process ing U P NO-SE Data valid. Local POD WA- POD Not OK OK U ord SVC contr Halse SVC (360 Mvar) 28
Testing the Local POD: Power flow (Sweden Norway) 1600 1500 Power Flow: Hasle No POD (Case 5) Incorrect POD (Case 6) Correct POD (Case 7) 1400 Active Power [MW] 1300 1200 1100 1000 900 0 2 4 6 8 10 12 14 16 18 20 Time [s] 29
Testing the Local POD: Voltage angles 44 42 Angle differences: Kristiansand - Nedre Rossaga No POD (Case 5) Incorrect POD (Case 6) Correct POD (Case 7) 40 38 Angle [deg] 36 34 32 30 28 0 2 4 6 8 10 12 14 16 18 20 Time [s] 30
Outline The Nordic power system WAMS activities, objectives and applications Power oscillation monitoring PMU measurements On-line monitoring From WAMS to WACS.. (ongoing and future work) Concluding remarks 31
Experiences and concluding remarks Several WAMS-applications have been assessed and tested by STATNETT Power oscillation monitoring (POM) is considered most useful by operators POM for post-disturbance analysis is demonstrated: Cause of oscillations easily identified from PMU measurements Promising experiences with on-line POM Amplitude, frequency and damping signals are robust when needed SVCs are shown to provide significant controllability on power oscillations: Implementation and testing of a Wide area POD is ongoing. 32