1. Activities of IEEE Power System Relaying Committee WG-24: Modification of Commercial Fault Calculation Programs for Wind Turbine Generators WG Chair: Sukumar Brahma, New Mexico State University WG Vice Chair: Evangelos Farantatos, EPRI 1

2. PSRC WG C24 Scope 1) To survey WTG manufacturers to determine what parameters they could provide that could be used by steady state short circuit program developers in various time frames. 2) Use the result of this survey to prepare a report that can be used by steady state program developers to refine their models. 2

3. Formation of WG C24 This WG was formed as a result of the work done in WG C17: Fault Current Contributions from Wind Plants. WG was formed in September 2014. We have had three meetings so far. Before talking about the activities of this WG, a summary of the C 17 report is in order. Report can be found at http://www.pes- psrc.org/Reports/Fault%20Current%20Contrib utions%20from%20Wind%20Plants.pdf 3

4. Type 1 WTG It was found that a conventional Thevenin model with X’ as defined above is acceptable. Available commercial software often require an equivalent sub transient reactance X d ’’, to model as a synchronous generator. 4

5. Type 2 WTG For higher operating slips, inclusion of rotor resistance was found to provide more accurate results. However, the maximum SC current would still be close to that of Type 1 (small operating slips means small external resistance). Z’ 5

6. Type III Responses – GE and EPRI 6

7. Type 3 WTG Very severe faults where the crowbar is applied and not removed, providing the fault current performance of a simple induction machine: Fig. (a). Faults of insufficient severity to cause crowbar operation, for which injected currents are controlled and performance is very similar to Type IV : Fig. (b). Faults of intermediate severity where the nonlinearities of crowbar operation are critical, result in complex behaviors. crowbar not activated. crowbar activated. (a)(b) 7

8. Type 3 Model Suggestion From C17 Report Maximum and minimum symmetrical short-circuit current magnitudes a) one cycle, 2) three cycles after fault application, as a function of residual MV bus voltage, for an example Type III wind turbine generator. Considers a range of pre-fault voltage Pre-fault power factor, and pre-fault generated power. 8

9. Type IV Responses – C 17 Report 9

10. Type 4 WTG Current is usually limited to the order of 1.1-1.5 per unit of rated current and only provides balanced positive sequence symmetrical current regardless of the type of fault. Manufacturer may provide the impact of terminal voltage on fault current contribution in a similar manner as described for Type III machines – for multiple time frames if applicable. Power factor is also required, because based on the mode of control and terminal voltage, current contribution can vary from purely active to purely reactive. 10

11. WG C24 Activity We have had following presentations: 1.“Phasor Domain Modeling of Converter Interfaced Renewables for Protection Studies”, by Dr. Evangelos Farantatos, EPRI. 2.“Short-Circuit Behavior of Type III and Type IV Wind Turbine Generators”, by Mr. Reigh Walling, Walling Energy Systems Consulting. 3.“Simulating Wind and Solar Plants in a Short Circuit Program”, by Dr. Sherman Chan, ASPEN. 4.“Modeling Wind Generation for Fault Analysis in CAPE”, by Dr. Sandro Aquiles-Perez, Electrocon. 11

12. WG C24 Approach Decide as a group what is needed to accurately model the voltage-controlled current source in phasor domain at various time-frames? Send these requirements to generator manufacturers and see if they are fine with providing this information. Write a report on how to create phasor domain models with this information. 12