On-line Voltage Instability Risk Identification Based on Phasor Measurements

Transcription

1 G.N.Taranto 1/23 Rio de Janeiro, RJ On-line Voltage Instability Risk Identification Based on Phasor Measurements Glauco N. Taranto COPPE/UFRJ Programa de Engenharia Elétrica

2 G.N.Taranto 2/23 Acknowledgements Acknowledgements Dr. Sandro Corsi (Centro Elettrotecnico Sperimentale Italiano)

3 G.N.Taranto 3/23 Presentation Outline Presentation Outline Introduction PMU Voltage Stability Background for the Method Utilized Proposed Algorithm for Identification Results Italian System Brazilian System (Preliminary Results) Concluding Remarks

4 G.N.Taranto 4/23 Introdução Introduction PMU First experiments back to the seventies The pioneers: Profs. Phadke and Thorp In Brazil: MedFasee Project (2003) Technology for synchronization Loran-C (in the past 100 khz) GPS (presently 2 MHz) Applications Monitoring (low sampling rate) Protection and Control (high sampling rate)

5 G.N.Taranto 5/23 Localization of PMUs in TVA (USA) Introduction

6 G.N.Taranto 6/23 Introduction Introduction Voltage Stability Short term From miliseconds to a few seconds Large perturbation Induction motor starting, HVDC Long term Work Focus From seconds to many minutes OLTC, OEL

7 G.N.Taranto 7/23 Background Background Based on: Measurements of voltage and current phasors Thevenin equivalent Impedance matching

8 G.N.Taranto 8/23 Background (Thevenin) Background r V L = r E Th Z Th r I L 1 equation 2 unknowns Z L = Z Th Maximal power transfer

9 G.N.Taranto 9/23 Installation Layout Background Source: Sakis Meliopoulos, IREP 2007

10 G.N.Taranto 10/23 VIP Voltage Instability Prediction Background Finding: relying only on voltage magnitudes to detect voltage instability is neither helpful nor reliable! Source: K. Vu and D. Novosel, Voltage Instability Predictor (VIP) - Method and System for Performing Adaptive Control to Improve Voltage Stability in Power Systems, US Patent No. 6,219,591, April 2001.

11 G.N.Taranto 11/23 Fundamentals Fundamentals assuming V β = cos 1 R Th L 0 cosθ ETh Eth is unknown Methods already proposed: 1) LMS 2) Tellegen s Principle

12 G.N.Taranto 12/23 Conceptual Analysis Fundamentals 1 Ω (?) Hint! Eth = 20 V 20 V (?) IL ZL V L Zth = 1 Ω Step Known Variables Estimated Variables Z L (Ω) I L (A) V L (V) E Th (V) Z Th (Ω) E Th (V) Z Th (Ω) ,5 19 0, ,22 17, , ,56

13 G.N.Taranto 13/23 Proposed Algorithm Proposed Algorithm Step 1 Estimate the initial value of E th o Step 2 Compute X th o Step 3 Compute E th (i) according to the logics of the previous numerical example Step 4 Compute X th (i) given E th (i) Step 5 Increment (i) and return to Step 3.

14 G.N.Taranto 14/23 Results Results The proposed algorithm was applied to the entire Italian System from real data System Characteristics: 2549 buses (380 kv and 220 kv networks) 2258 transmission lines and transformers 325 generators 50 GW of load Dynamic models for OLTCs, OELs, voltage regulators and speed governors Application to load and transit buses Sampling rate 20ms (1 phasor/cycle in 50Hz)

15 G.N.Taranto 15/ kv Network Results Milan Florence

16 G.N.Taranto 16/23 Brugherio 380kV Bus Results

17 G.N.Taranto 17/23 Baggio 380kV Bus Results

18 G.N.Taranto 18/23 Sensitivity to the Sampling Rate Results

19 G.N.Taranto 19/23 Tests in the Rio Area Results Tests are still preliminary Made possible via Anatem from CEPEL Case and models obtained from ONS webpage (February/2007) Load ramp increase Summary submitted to SEPOPE 2008

20 G.N.Taranto 20/23 Preliminay Tests in the Rio Area Results I V I I

21 Cachoeira Paulista 500kV Z_Thevenin x Z_carga G.N.Taranto 21/23 Results

22 G.N.Taranto 22/23 Concluding Remarks Concluding Remarks The phasor measurements can efficiently be utilized in voltage instability prevention. High sampling rates are necessary. Prediction of voltage instability in a region can be made without extensive use of the communications resources. It is possible to proposed more sophisticated control logics relying on data synchronization via GPS. Comprehensive results from the Italian System and preliminary ones from the Brazilian System encourage further research on this topic.

23 G.N.Taranto 23/23 Rio de Janeiro, RJ THANKS!