Web URL: Guidelines for Data Selection, Validation, and Submittal.pdf

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1 Document Title File Name Category Guidelines for Thermal Governor Model Data Selection, Validation, and Submittal to WECC WECCGuidelinesforThermalGovernorModeling.pdf ( ) Regional reliability standard ( ) Regional criteria ( ) Policy (X) Guideline ( ) Report or other ( ) Charter Document date May 19, 2010 Adopted/approved by M&VWG Date adopted/approved November 4, 2002 Custodian (entity M&VWG responsible for maintenance and upkeep) Stored/filed Previous name/number Status Physical location: Web URL: Guidelines for Data Selection, Validation, and Submittal.pdf (X) in effect ( ) usable, minor formatting/editing required ( ) modification needed ( ) superceded by ( ) other ( ) obsolete/archived)

2 WECC Guideline: Guidelines for Thermal Governor Model Data Selection, Validation, and Submittal to WECC Date: 11/4/2002 Introduction This guideline provides instructions regarding modeling thermal governors for generating units. It was written to resolve issues noted in comparing simulation results to measurements of frequency and provided new guidance for modeling governors. Approved By: Approving Committee, Entity or Person Date WECC Modeling and Validation Work Group November 4, 2002

3 GUIDELINES FOR THERMAL GOVERNOR MODEL DATA SELECTION, VALIDATION, AND SUBMITTAL TO WECC Prepared by the Governor Modeling Task Force WECC Modeling & Validation Work Group October 9, 2002 Revised November 4, 2002

4 Guidelines for Thermal Governor Model Data Selection, Validation, and Submittal to WECC Introduction Studies conducted during 2002 have demonstrated that representing base loading of generators and generator load controllers has a dramatic effect on simulation results, not only in frequency deviation studies (reserve, under frequency load shedding, etc.), but will impact the results of many system stability studies, such as those used to set transfer limits, remedial action, etc. The results of these studies and the new recommended models for thermal turbine-governors were distributed to WECC members in a report by a task force of the Modeling and Validation Work Group titled "New Thermal Turbine Governor Modeling for the WECC". The report clearly indicates the significant improvement in system simulations as a result of the new thermal modeling and the corresponding inadequacies of the existing thermal governor models. The new modeling will significantly improve the predictability of performance of the power system during major generation and RAS outages. (Fig. 1) A governor modeling workshop was held in Salt Lake City on August to disseminate the information from recent studies and to describe to generation owners some newly developed models and what information is required to assign data to the model variables 1. Figure 1 - Improvement in Simulation Accuracy with New Modeling Model description Two new models have been developed for use in WECC studies. The ggov1 model, referenced in the report is a generic thermal governor/turbine model that incorporates base loading and a load controller. The model, lcfb1, is identical in structure to the load controller portion of ggov1, and can be used in tandem with any governor model 1 Workshop material is available on the WECC website

5 currently defined in the GE PSLF program (see figure 2 for model diagrams). See Appendix 1 of the report listed above for additional information. Thermal plants not currently modeled with a governor in the WECC database should be added using the ggov1 model. All gas turbine units should use the ggov1 model, as all other gas turbine models will not be supported in future releases of GE PSLF. Hydro units that operate under load control should also use the lcfb1 model in addition to the appropriate hydro governor model. Existing ieeeg1 models may be used with the addition of the lcfb1 load controller model if it applies. Alternatively, the new ggov1 model may be used for such units with appropriate data supplied for it. Upon initialization, base-loaded units and load-controllers are assigned values in the ggov1 and lcfb1 models equal to the generator dispatched value specified in the power flow data. If the effects of a load (or any set point other than frequency) controller are to be included, the output of the unit will be reset to the value of P MWSET. The speed at which the resetting takes place is controlled by the value of K IMW (KI in model lcfb1.) - 2 -

6 Figure 2 - ggov1 (above) and lcfb1 (below) models Model Data and Validation Requirements Whether a unit is base loaded and the value of K IMW (or KI) for units with load controllers are the important pieces of new information that must be added to the database and validated through measurement. Current WECC policy requires that all generation owners submit appropriate computer model data to represent their machines and associated equipment along with recorded data that validates the accuracy of the computer models. It is therefore required that the data for the new models discussed herein be validated by comparing actual measured electrical power output response data of each unit to the computer modeled simulation response. Typical responses of SCADA recordings of thermal units and simulations with the new governor model and the existing model (base case) are shown in Figs. 3a, 3b and 3c

7 Figure 3a Example of Slow Load Controller Response vs. Existing and New Models, kimw = Fig. 3b. Example of a Fast Load Controller Simulation with the new ggov1 model, kimw=

8 Fig. 3c. Example of a Base Loaded unit Simulation with the new ggov1 model Since governor response occurs as a result of system frequency deviation from 60 Hz, validation data is best obtained during sudden, large generation trips. The recorded data necessary to perform the model validation consists of system frequency and electrical power output of the generator in question. Recordings of system frequency of several past and possible future underfrequency events will be available from the WECC website. The only recordings necessary for the generator owner to obtain during one of these listed events (or future events) will be the electrical power output and frequency. Disturbances that are suitable for validation are those in which system frequency drops 0.15% or more (59.90 Hz or below). A generation trip of 800 MW or greater will usually result in the appropriate frequency deviation. Future disturbances that are deemed suitable for validation will be announced through WECC information distribution channels so that generator response data can be obtained from recording equipment in a prompt time frame. For the purpose of validation, the event recordings of the MW output of the generator must be of sufficient resolution, sampling rate, and length to determine the change in power output of a generator. The recording should have a resolution not greater than 1 percent of the rated generator output. The MW data should be recorded at least every 4 seconds or less. The data record should extend a period of seconds or more. The suggested methods of obtaining measurement data are: 1. SCADA (either local systems or those used for dispatch control centers) 2. Data loggers 3. Digital Excitation/Governor event capturing systems 4. Dedicated monitoring systems (PPSM, disturbance monitors, machine condition monitors, data acquisition systems) - 5 -

9 5. Test Instrumentation (Oscillographic recorders, PC based recorders, virtual instruments, etc., set to automatically trigger a recording when system frequency dips below 59.9 Hz) Recordings of system frequency for the following past underfrequency events will be available from the WECC website and may be used for data validation 1. May 18, 2001 tests (NW and Hoover trips) 1250 MW and 750 MW respectively (10:40 and 10:20 PDT) 2. June 7, 2000 trip tests (750 MW) 3. July 27 (19:19 PDT), 2002 Four Corners trip (2065 MW) 4. July 15 (13:04), 2002 NW RAS trip (2350 MW) 5. July 16 (15:41 PDT), 2002 NW RAS trip (2350 MW) 6. June 6 (13:47 PDT), 2002 PDCI loss ( 2800 MW ) 7. June 3, 2002 Diablo Canyon trip (950 MW) 8. Recent Colstrip trips (2000 MW) 9. October 8, 2002 (15:31 PST) 2900 MW NW RAS trip Future Events: When an underfrequency event occurs in the future that is suitable for model validation, WECC will send out a notification within 24 hours so that the generation owners can retrieve the captured validation data. The owner should also record the manner in which his unit was operated at that time. A file containing the system frequency vs. time data to be used for validation will be sent out by WECC at this time. The Owner may request SCADA records of the unit from his Control Area Operator. If SCADA is not available, the Owner should record his unit s response to the event using one of the methods described earlier. Validation of data 1. Using the frequency data as an input, perform a computer simulation of the event using the new governor model and data. {There are two methods, one using epcls with recorded data, and the other using the pfs frequency profile model. Both methods are described below.) 2. Verify the simulated response is similar to the measured, recorded response. 3. Adjust the model parameters if necessary to improve the match. Model data will be considered validated when the power output response of a generator in simulation of an event closely resembles the actual recording of the event. The simulated response should be demonstrated to be similar to the measured response over a 60 second time period. An example of such a comparison is illustrated in figure 3. The response plots should be submitted to WECC as soon as the comparison data is available. The model data used for the simulated response should be listed along with the response plots

10 The most appropriate way of performing the model validation is to perform the simulation using the measured frequency data obtained during the actual measured event. A typical recording of system frequency during such an event is shown in figure 4. This type of validation can be accomplished by using any of the following methods: 1. Using WECC provided epcls to automatically simulate the validation event using the GE PSLF program. See Example 1, below. 2. Using a current WECC data base case, approximate the actual event by tripping enough generation in the simulation to produce a frequency dip that closely approximates the actual event for comparison. See Example 2 below. 3. The pfs utility in the GE PSLF program, using a frequency profile. See Example 3 below. 4. A small, stand-alone program by GE that will allow this to be done is currently being developed and will be available from the WECC staff in November This program will only require the user to input the model data for the appropriate model. See Example 4 below. Typical Questions to be asked by the Owner before selection of the appropriate model: To facilitate answering these questions and in the selection of the appropriate governor parameters, the Owner may refer to the diagram of approximate responses in Figure Is the generator unit normally operated in a mode that can be considered base loaded? (For definition of base loaded, see lowest Base Loading Response Box in Fig.5.) 2. Is the generator unit normally operated under load setpoint control, or any other mode of control that will override automatic action of the governor responding to changes in system frequency? Other examples of these control modes may be temperature limiters, etc. 3. If the answer to question 2 is yes, is the response time of the dominant controller fast or slow as indicated on the time scale in figure 5. (See Response Boxes for Fast Controllers Code T1 2 and Slow Code T2 Controllers in Fig.5.) 4. Is the generator unit normally operated in a mode that can be considered Responsive? (See Upper Responsive Box in Fig.5 for Code T3.) 5. Does the generating unit normally respond to AGC signals? 6. If the generator is currently represented in the WECC database without an excitation system model, the type of exciter should be specified, e.g., Fully static, Rotating DC, Rotating AC Brushless, etc., or manufacturer and model information, if known. 2 As discussed at the Workshop, the recommended Code parameters are typical values and the Owner should select appropriate values to suit his application. For example, Code T1 could vary between 0.01 to 0.02 or greater, and Code T2 could vary between to

11 It is realized that units may be operated in different modes from day to day, or even hour to hour, and that the responses to these questions will vary accordingly. In these cases, it is up to the owner to decide which mode the unit is most likely to be operated in at any given time. Most of the base cases of concern are intended to represent the system during daily peak loading conditions. Figure 5 - Response Guideline Additional Data Required Also critical to the accuracy of WECC system studies is the correct representation of excitation systems. There are a large number of generators in the WECC database currently represented without exciter models. It is required that all generators be modeled with the appropriate and validated exciter models. See attached Excel spreadsheet for details of Units Without Models

12 Submittals Submittals shall be made to: Donald Davies WECC phone: Arapeen Drive Salt Lake City, Utah

13 Example 1 Validation example using WECC supplied epcls and GE PSLF A detailed, step by step, example illustrating validation and use of WECC epcls is given below: 1. Obtain the May 18 th Test epcl files and the data file for the May 18 th Test recording from the WECC BBS. Put all the files, except "event.p" in your working directory. Place the "event.p" in your upslf131\stdepecl\" directory. 2. Run the PSLF program. 3. The example given is for two typical generators UnitXX and UnitYY. These units are dispatched with identical MW loadings in order to compare the effect of fast and slow controllers. 4. Load the files unitxy.sav for the powerflow and unitxy.dyd for the dynamic stability run. 5. The unitxy.dyd file has two typical governor models, one a ggov1 model and the other an ieeeg1 with lfcb1 with assumed parameters for fast and slow ggov1 models. (If given identical parameter values, the responses will be identical.) 6. The directory should also contain a data file e dat that has in it data for Unit XX and UnitXY from the May 18th recordings. 7. Run the epcl RUNunitXY.p which will run the detailed simulation. 8. Plot the electrical power output of the UnitXX and UnitYY from the PSLF Plot program. (See Fig.6). If the recording of the UnitXX and UnitYY were taken on the HV side of the main transformer (as many SCADA recordings are taken), the MW readings will be the generator output minus the auxiliary load of the unit. 9. Compare the output of PSLF with the May 18 th recording of unitxx and unityy generators during the May 18 th Test. 10. Change the kimw parameter of the ggov1 models as appropriate to achieve the best comparable simulation with the May 18 th recordings. 11. A number of runs may be needed to optimize this selection of the ggov1 parameter kimw. However, these runs are very fast because of the small system simulated. 12. If the generator was clearly in base loaded operation during the May 18 th test, denote this with the appropriate flag by placing a 1 in Column B of the gens table in the PSLF powerflow program. Run the dynamic simulation. Again compare the output of PSLF with the May 18 th recording for confirmation. 13. Submit the model and plots of the simulation to WECC

14 Fig. 6 Example 1 - Simulation of Fast and Slow Load Controllers Using the WECC epcls. (The figure shows that the validated governor model is best represented by a Slow Controller ggov1 model with the parameter kimw = )

15 Example 2 Validation example using a typical two Palo Verde Unit generation drop in GE PSLF A detailed, step by step example illustrating validation using a current full-loop WECC data base case is given below: 1. Run the PSLF program with a current basecase example a Light Spring Case. 2. Load the files xxx.sav for the powerflow and xxx.dyd for the dynamic stability run. 3. The xxx.dyd file should have entered in it the typical ggov1 model with assumed parameters for the generator you wish to simulate. 4. Run the simulation by tripping 2-Palo Verde Units. (If another disturbance is simulated, note that using the current model database, tripping the same generation as in the actual event will not produce enough frequency deviation to properly validate the model. The optimistic frequency response will result in a pessimistic governor response, so additional generation will have to be tripped in the simulation 3.) A 30 second run is a minimum, but for a slow controller a second run may be needed. 5. Plot the output of your generator electrical power from the PSLF Plot program (see Figure 7). 6. Compare the output of PSLF with the May 18 th (or other disturbance) recording of your generator obtained from SCADA or disturbance recording. 7. Change the kimw parameter of the ggov1 model as appropriate to achieve the best comparable simulation with the disturbance recording. 8. A number of runs may be needed to optimize this selection of ggov1 parameter kimw. These runs could take time because system simulated is the full-loop WECC system. However, the advantage of this method is that it could be done immediately without special epcls or special case files. 9. If the generator was clearly in base loaded operation during the disturbance, denote this with the appropriate flag by placing a 1 in Column B of the gens table in PSLF powerflow program. Run the dynamic simulation. Again compare the output of PSLF with the disturbance recording for confirmation. 10. Submit the model and plots of the simulation to WECC. The figure below shows an example of this type of validation, in which a two unit Palo Verde trip was used to initiate the frequency deviation. 3 This illustrates the current deficiency in representing governor response in the database and the need to incorporate the additional data discussed herein

16 Fig. 7 Example 2- Simulations of Fast and Slow Load Controllers using loss of two Palo Verde units

17 Example 3 Validation Method using pfs utility in GE PSLF Step by step example illustrating validation and use of pfs utility for the May 18 th Test. 1. Obtain the May 18 th Test Profile from WECC see Figure 8 below Fig. 8 Example 3 - May 18 frequency recording at the Malin 500 kv bus 2. There are 4 points on the frequency profile as shown in the Figure which will be used in the pfs model as a function of input frequency and time. (see unitxypfs.dyd file to be downloaded from the WECC BBS). 3. Run the PSLF program 4. The example given is for a typical generator. Modify the parameters to suit. 5. Load the files unitxy.sav for the powerflow and unitxypfs.dyd for the dynamic stability run. 6. The UnitXYpfs.dyd file has a typical ggov1 model with assumed parameters plus the pfs model. 7. Run the epcl unitxypfs.p which will load the pfs model using the unitxypfs.dyd. 8. Plot the electrical power output of the units from the PSLF Plot program. 9. Compare the output of PSLF with the May 18 th recording of the generator during the May 18 th Test. 10. Change the kimw parameter of the ggov1 model as appropriate to achieve the best comparable simulation with May 18 th recording. 11. A number of runs may be needed to optimize this selection of ggov1 parameter kimw. However, these runs are very fast because of the small system simulated

18 12. If the generator was clearly in base loaded operation during the May 18 th test, denote this with the appropriate flag by placing a 1 in Column B of the gens table in the PSLF powerflow program. Run the dynamic simulation. Again compare the output of PSLF with the May 18 th recording for confirmation. 13. Submit the model and plots of the simulation to WECC

19 Example 4 Validation example using stand alone program (for non GE PSLF users) Details for the running of the stand-alone program are identical to the pfs model in Example 3 except that the program represents a small system