PMU-Based Distributed State Estimation with the SuperCalibrator PSERC Seminar June 17, 2008

Transcription

1 PMU-Based Distributed State Estimation with the SuperCalibrator Seminar June A. P. Sais Meliopoulos Georgia Power Distinguished Professor School of Electrical and Computer Engineering Georgia Institute of Technology Seminar June

2 Presentation Outline The Need for State Estimation Evolution of State Estimation Technology GPS Synchronized Measurement Technology The SuperCalibrator Approach Implementation and Demonstration (IWAPA May ) Future Directions Seminar June

3 The Need for State Estimation 1965 Blacout Edward Teller (member blue ribbon committee) compared the electric power system with a dinosaur: Big Body Small Brain reflecting on the fact that at the time the communications infrastructure and information transmittal was in its infancy. Seminar June

4 Development of the State Estimator ca 1968 Basic Assumptions: Positive Sequence Model P Q Measurement set Near-Simultaneous Measurements Single Frequency Implications: Balanced Operation Symmetric Power System Biased State Estimator Iterative Algorithm Hardware: Sensors for P Q and Accuracy: 1 to 3% Communications mostly dedicated SCADA Seminar June

5 Evolution of Supervisory Control State Estimation in Power Systems Seminar June

6 SCADA Evolution Indicator Control SCADA circa 1923 To Data Base Remote Access Control Center User Interface Encoder Decoder Communications Terminal GPS RTU IED Disturbance Recorders Relays SCADA circa 2003 SCADA Communications Terminal Local Computer Seminar June

7 Forward to August 2003 From US-Canada Power System Outage Tas Force Contributing Factors Inadequate Situational Awareness Recommendation 22 Evaluate and adopt better real-time tools for operators and reliability coordinators. Seminar June

8 Present Operating Model Real Time Model State Estimation Applications Load Forecasting Optimization (ED OPF) AR Control Available Transfer capability Security Assessment Congestion management Dynamic Line Rating Transient Stability EM Transients etc. isualizations Marets: Day Ahead Power Balance Spot Pricing Transmission Pricing (FTR FGR) Ancillary Services Seminar June

9 Two Major Issues (a) Data Reliability/Accuracy and (b) Automation Basic Tools for Grid isibility: SCADA (unfiltered) and SE (filtered) The objective of SE is to provide a reliable real time model How Well is it Done What is the Accuracy Can We Mae All Information Available to All Constituent Part of the Electric Grid Enterprise? (The Promise of Automation) Seminar June

10 Potential Transformer Instrumentation Cables Present State of the Art Measurement Layer Phase Conductor v(t) i(t) Current Transformer IED endor D Relay endor C (a) SCADA Transducers: 1 to 3% (b) Modern Relays: 0.1 to 1% (c) GPS-Synchronized Equipment: Magnitude 0.1% to 1% Phase: 0.01 to 0.05 Degrees at 60 Hz. (Systematic Errors Can Be Easily Accounted for) (b) System Asymmetries (4 to 6% differences among phases) v 1 (t) i 1 (t) v 2 (t) i 2 (t) Attenuator Burden Attenuator Burden PMU endor A Anti-Aliasing Filters PMU endor C (c) System Imbalance (0 to 12% among phases based on personal observations) (d) Instrumentation Channel Errors (0.02 to 3%) Seminar June

11 Instrumentation Errors: oltage Measurement Example Phase A Magnitude Error: 1.46% Phase A Phase Error: 0.41 degrees Seminar June

12 Why Do We Need High Accuracy? If we consider a 50 mile long 230 line rated 400 MA and evaluate the required accuracy in voltage magnitude and phase angle measurements to achieve a 1% accuracy in power flow then we have the following pairs: oltage Magnitude: 0.5% Phase Angle: 0 degrees oltage magnitude: 0.4% Phase Angle: 0.03 degrees oltage magnitude: 0.3% Phase Angle: 0.05 degrees oltage magnitude: 0.2% Phase Angle: 0.09 degrees Use of raw data for various monitoring prediction and control may lead to large errors Seminar June

13 Traditional State Estimator Basic Assumptions: Positive Sequence Model P Q Measurement set Near-Simultaneous Measurements Single Frequency Implications: Balanced Operation Symmetric Power System Biased State Estimator Iterative Algorithm Sources of Error: GPS-Synchronized Equipment: Magnitude 0.1% to 1% Phase: 0.01 to 0.05 Degrees at 60 Hz SCADA: 1 to 3% System Asymmetries (4-6% differences among phases) System Imbalance (0-12% among phases) Instrumentation Channel Errors (0.02-3%) Time Response: Centralized State Estimator Response (minutes) Seminar June

14 Important Example What Are the Limits of Traditional State Estimation? Device Terminal Multimeter Case: Device: Side 1 Side 2 oltages PANROM_A PANROM_B PANROM_C PANROM_N Currents PANROM_A PANROM_B PANROM_C ENTERGY: Panama-Romeville 230 Line - Dynamic Rating project Panama-Romeville 230 Transmission Line Ref 3 Phase Power oltage Per Phase Power Ib bn cn Ic Program W inigs - Form IGS_MULTIMETER Ia I pos 369.9e 348.7e Current Impedance j11.56 Seminar June j10.56 S an Ia 0 A L-G L-L Close Phase Quantities Symmetric Comp P MW Q Mar S = MA PF = % an = Deg bn = Deg cn = Deg Ia = A Deg Ib = A Deg Ic = A Deg Device Terminal Multimeter Case: Device: Side 1 Side 2 oltages PANROM_A PANROM_B PANROM_C PANROM_N Currents PANROM_A PANROM_B PANROM_C ENTERGY: Panama-Romeville 230 Line - Dynamic Rating project Panama-Romeville 230 Transmission Line 14 Ref an pos 3 Phase Power oltage Per Phase Power Program W inigs - Form IGS_MULTIMETER 130.7e 131.0e In Iz Current Impedance S p Ip j5.908 j5.613 L-G L-L 0 0 Close Phase Quantities Symmetric Comp P MW Q Mar S = MA PF = % p = Deg n = Deg z = Deg Ip = A Deg In = A Deg Iz = A Deg

15 GPS Synchronized Measurements Enable Distributed State Estimation Seminar June

16 History of GPS-Synchronized Measurements Efforts to Develop Technologies with Accurate Time Synchronization Started in the Early 80 s. Examples: Missout & Girard 1980 Bonanomi 1981 Phade These efforts resulted in technologies with time synchronization accuracy that was several tens of microseconds. In 1992 Macrodyne (Jay Murphy) introduced the first PMU (Phasor Measurement Unit) capable of taing measurements with synchronization comparable to GPS cloc accuracy (microsecond accuracy) Seminar June

17 Memory Macrodyne 1620 PMU Released to Maret January 1992 Input Protection & Isolation Section A/D Converter ( Modulation) Optical Isolation Digitized Data 2880 s/s GPS Antenna CHARACTERISTICS Optical Isolation GPS Receiver 1PPS IRIGB Individual Channel GPS Sync Analog Inputs : 300 I : 2 Input Protection & Isolation Section A/D Converter ( Modulation) Sampling Cloc Optical Isolation Optical Isolation Master Worstation Digitized Data 2880 s/s PLL P RS232 Data Concentrator (PC) Display & Keyboard Common Mode Rejection Filter with Optical Isolation 16 bit A/D Modul. Time Precision 1 s 0.02 Degrees at 60 Hz Seminar June

18 Filter NYPA s Harmonic Measurement System Using GPS Synchronized Measurements (Macrodyne s PMUs) Asymmetric Power System Model New Yor Power Authority First Wide Area Monitoring System In Eastern Interconnection I GPS Antena PMU Bloc Diagram GPS Receiver A/D Micro processor Phasor data (time stamped) Serial Communication Port Global Time Reference (GPS) PMU Computer PMU Computer PMU Computer Harmonics Data Concentrator (Located in Atlanta) NYPA Project Launched: 1993 Completed: 1998 NYPA: Shalom Zelingher Bruce Fardanesh GaTech: Meliopoulos & Coinides To Control Center ADD Bulletin Board System GIC Data Concentrator Located at NYPP Seminar June

19 The SuperCalibrator Concept Develop a State Estimator that Addresses all of the Above Issues IMPORTANT FEATURE: The presence of GPS Synchronized Measurements Allows Full Decentralization of the State Estimation Process IMPLEMENTATION: Formulate the State Estimation Problem for Each Substation. Transport the Substation State Estimates to Control Center and Synthesize the System State Seminar June

20 The SuperCalibrator is a Substation Based State Estimator with the Following Features: Eliminates Model Biases (Full Three-Phase Model with Neutrals etc.) Eliminates Imbalance Biases (Single Phase or Three Phase Measurements) Eliminates Biases From Instrumentation Channel Errors (Model is Augmented with Instrumentation) Robustness (Model Quadratization) Seminar June

21 The SuperCalibrator Concept The SuperCalibrator is conceptually very simple. The basic idea is to provide a model based error correction of substation data and in particular RELAY DATA. The basic idea is to utilize a high fidelity model of the substation (three-phase breaeroriented model instrumentation channel inclusive and data acquisition model inclusive). Then all substation data obtained with any device PMU meter relay SCADA etc. is expressed as a function of the state of the high fidelity substation model. The SuperCalibrator uses (a) a static state estimator algorithm and (b) a dynamic state estimator algorithm. GPS Synchronized Relays Mae the Process Robust and the Results Globally alid Seminar June

22 Potential Transformer Instrumentation Cables LAN LAN Encoding/Decoding Cryptography Data Processing SuperCalibrator Schematic Representation Measurement Layer Phase Conductor i(t) IED endor D v(t) Current Transformer Relay endor C FireWall i 1 (t) i 2 (t) Attenuator Burden PMU endor A Super- Calibrator v 1 (t) v 2 (t) Attenuator Anti-Aliasing Filters PMU endor C Burden Model Based Data alidation and Information Extraction (Redundancy Bad Data Rejection Statistical Estimation etc.) Seminar June

23 SuperCalibrator Implementation on the IWAPA System Seminar June

24 Demonstration (Pilot) Project Pilot project for demonstrating the application of the SuperCalibrator concept for distributed state estimation on the US irgin Islands power networ. St. John Island St. Thomas Island US irgin Islands consist of the main islands of St. Croix St. John and St. Thomas along with many other surrounding minor islands. The networ is a stand-alone power system and is not connected to the US national power grid. The SuperCalibrator is implemented on the St. Thomas and St. John Islands power system the system has five substations and a generating plant. Each substation has at least one SEL 421 relay or SEL 734 with GPS-synchronized measurement capability. Seminar June

25 Implementation Substation Model Substation State Measurements Pseudo-measurements Estimation Method Seminar June

26 Substation Model Physically Based Component Modeling Explicit Representation of Phase Conductors Neutrals Ground Conductors and Grounding accounts for ground potential rise Explicit Representation of Breaers Switches Explicit Representation of Instrumentation and Relay Inputs Integrated with the Power System Seminar June

27 SuperCalibrator Implementation Substation Configuration Long Bay 3D Model Seminar June

28 SuperCalibrator Implementation Substation Configuration Long Bay Seminar June

29 SuperCalibrator Implementation Substation Configuration Long Bay Seminar June

30 SuperCalibrator Implementation Substation Configuration Long Bay Seminar June

31 SuperCalibrator Implementation Substation Configuration Long Bay Seminar June

32 SuperCalibrator Implementation Substation Configuration Long Bay Seminar June

33 SuperCalibrator Implementation State Estimation Configuration Long Bay Seminar June

34 SuperCalibrator Implementation State Estimation Configuration Long Bay Seminar June

35 Seminar June State Definition Substation 1e 2e 3e 4e 1s 2s Definition of State for a Substation 1s ector of dimension 4: n s c s b s a s s ector of dimension 4: n s c s b s a s e ector of dimension 4: n e c e b e a e e ector of dimension 4: n e c e b e a e SuperCalibrator Static State Estimation Substation State

36 SuperCalibrator Measurement Set Any Measurement at the Substation from Any IED (Relays Meters FDR PMUs etc.) Data From at Least one GPS-Synchronized Device Pseudo-Measurements Kirchoff s Current Law Remote End State Measurement Missing Phase Measurements Neutral/Shield Current Measurement Neutral oltage Seminar June

37 Seminar June SuperCalibrator Measurement Set GPS-Synchronized Measurements N A z 1 1 C B m A m C B A T A d A d C I z GPS-Synchronized Measurements oltage Phasor Current Phasor

38 SuperCalibrator Measurement Set Non-Synchronized Measurements A sync A meas e j alpha is a synchronizing unnown variable Cos and sin of alpha are unnown variable in the state estimation algorithm There is one alpha variable for each non-synchronized relay Seminar June

39 SuperCalibrator Measurement Set Non-Synchronized Measurements z Non-Synchronized Measurements oltage Magnitude 2 z 2 P d1 A A N 2 A r N r A i N i Real Power Example 1 Re A C T d1 A A B C m A m B C 2 * 2 A A sync real j( A A cos real Example 2 sin meas e j A imag A imag sin cos Seminar June

40 I I S R SuperCalibrator Measurement Set: Remote End State Measurement Line i Equations Y Y Y Y S R Substation S I S Line i R I R Solve for at remote end pseudo m 1 1 R I Z22Y22 Z21IS I Z22Y22 Z22Y21 S Expected Error: 0.01% Where: Z Z Z Z Y Y Y Y Demonstration Example Seminar June

41 SuperCalibrator Measurement Set: Kirchoff s Current Law I 4 I 5 I 6 I 1 I 3 Substation I 2 I I 1 2 I 6 I I 0 I I I m 0 Expected Error: 0.001% Expected Error: 0.001% Seminar June

42 SuperCalibrator Measurement Set: Missing Phase Measurements Assume There is a Phase A oltage Phasor Measurement. Assume there is no Phase C Measurement. THEN: 0 pseudo m e j240 s / n a 0 Expected Error: Less than 3% Seminar June

43 Seminar June SuperCalibrator: Estimation Method syn non phasor J Min * N A z 1 1 C B m A m C B A T A d A d C I z 2 2 N A z * 1 1 Re C B m A m C B A T A d A A d C P z GPS-Synchronized Measurements Non-Synchronized Measurements oltage Phasor Current Phasor Real Power oltage Magnitude i N A i r N A r

44 SuperCalibrator: Estimation Method * Min J phasor non syn Solution x 1 x A z h x where: A H WH T 1 H T W Efficiency Example Long Bay Substation High End PC One Iteration: multiply-adds (0.002 seconds) Compute Matrix A: ariable (sparsity) Almost Invariant (0.010 secs) Seminar June

45 State Estimation Performance Evaluation Chi-Square Test Step 1: Compute the state estimate x* * Step 2: Evaluate the function J r H W r Step 3: Compute p() = 1 - P(a/ 2 m-n) a 2 where: P(a/ 2 u) is the probability that J < a and u is the degrees of freedom Seminar June

46 Performance Achievement isualization is Updated 4 Times a Second Seminar June

47 Overall Performance Metric Chi-Square Test Master Report Provides Overall SE Performance in Terms of factor Seminar June

48 SuperCalibrator Storing and Retrieving Data Program XfmHms - Page 1 of 1 c:\wmaster\xfm\datau\viwapa_001 - Apr :42: samples/sec Samples Long_Bay_Substat_Frequency (Hz) IW_LONGBAY_B305_Frequency (Hz) IW_LONGBAY_B307_Frequency (Hz) SelFmpDevice_Frequency (Hz) SelFmpDevice_Frequency (Hz) Long_Bay_Substat_1LPM_PHA (Degrees) IW_LONGBAY_B305_1LPM_PHA (Degrees) IW_LONGBAY_B307_1LPM_PHA (Degrees) SelFmpDevice_1_PHA (Degrees) SelFmpDevice_1_PHA (Degrees) :43 16:44 16:45 16:46 16:47 16:48 16:49 Seminar June

49 SuperCalibrator Storing and Retrieving Data Phase Angle (Degrees) Tutu Long Bay East End :46:02 16:46:06 16:46:10 16:46:14 16:46:18 16:46:22 16:46:28 Seminar June

50 SuperCalibrator Implementation Example of Measurement/Pseudo-M Count Long Bay Long Bay Substation Number of Analog Measurements: 318 real Number of Pseudo-measurements: 72 real Number of Status Measurements: 15 Future: Becwith Relay Measurements: 2 Number of States: Long Bay 35 Bus: 3 (complex) Long Bay 13 Bus: 3 (complex) RHPP 35 Bus: 3 (complex) East End 35 Bus: 3 (complex) Redundancy 886% Seminar June

51 SuperCalibrator: Estimation Method Scalability Large Substation Implementation Assumptions: 3 levels70 relays 5 PMUs 35 breaers Number of Analog Measurements: 1500 real Number of Pseudo-measurements: 340 real Number of Status Measurements: 35 Number of States: 54+65=119 Efficiency High End PC One Iteration: multiply-adds (0.022 seconds) Compute Matrix A: Almost Invariant - Compute Once Upon SetUp Seminar June

52 Summary The SuperCalibrator Concept was Introduced to Solve the Limitations of Traditional State Estimators: 1. System Asymmetries 2. oltage Imbalance 3. Instrumentation Channel Error. The SuperCalibrator Concept has Been Successfully Demonstrated on Several Systems Including a Small Five-Substation Power System State Estimation rates of FOUR PER SECOND has been achieved The SuperCalibrator Approach is Scalable to Any Size System Seminar June

53 Future Directions Seminar June

54 Present State of the Art: Separation of C&O and P&C Control & Operation Real Time Model State Estimation Applications Load Forecasting Optimization (ED OPF) AR Control Available Transfer capability Security Assessment Congestion management Dynamic Line Rating Transient Stability EM Transients etc. isualizations Marets: Day Ahead Power Balance Spot Pricing Transmission Pricing (FTR FGR) Ancillary Services Protection & Control Component Protection generators transformers lines motors capacitors reactors System Protection Special Protection Schemes Load Shedding Out of Step Protection etc. Communications Substation Automation Enterprize InterControl Center The Infrastructure for Both Functions is Based on Similar Technologies: Thus the Opportunity to Merge Cut Costs Improve Reliability Seminar June

55 Project T38 Substation of the Future From This To This Seminar June