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Challenges building resources near series capacitors

This update highlights the challenges faced in connecting near series capacitors. Technical issues, SSR events, and the need for extensive studies and manufacturer collaboration are discussed. Findings suggest that SSR studies for units located close to series caps are complex and time-consuming.

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Challenges building resources near series capacitors

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  1. Challenges building resources near series capacitors - An Update to the RPG 11/14/2017 presentation - ERCOT System Planning RPG, 1/22/2019

  2. Recap • On 11/14/2017, ERCOT made a presentation to RPG, warning of challenges connecting near series capacitors. • Around the same time, • Three SSR events occurred with Valley Wind • Correcting the issues took over a year and dozens of calls with manufacturers • Since then, • Several GINR-SSR studies for units locating close to series caps have encountered unanticipated challenges

  3. Why is it so challenging to connect near series caps?

  4. Technical Challenges – Connecting Near Series Caps • Compensation level seen by IRR can be >100% • Potential Challenges: • More SSR risk • VRT / tripping issues • “Energy accumulation” and inverter saturation • Voltage Profile • Voltage Control This slide presented 11/14/2017 to RPG

  5. “Energy Accumulation” • Series capacitor will naturally charge up during a fault • Upon clearing fault, capacitor discharges: • Creates an unbalanced voltage transient • May saturate or trip radially connected generation • Inverter controls may saturate • Results in SSR even though SSR mitigation is installed • May result in tripping of IRR

  6. Generation Interconnection Studies

  7. Studies Become More Complex Near Series Caps • Close to series capacitors, effect of nearby generation is amplified • May have a study where individually each wind farm is okay but all together show SSR • Valley SSR event highlighted the interaction of neighboring projects • Not all OEM PSCAD models work well together in simulations  more study time • Nearby projects create additional sensitivities  more study scenarios • More time required to set up simulation and more data required

  8. FIS SSR Study Observation • For generators located close to series caps, not uncommon to identify SSR issues and other issues, including overvoltage. • Extra study time required (weeks~months) for TSPs, developers, and ERCOT to work with manufacturer to address the issues

  9. Key Takeaways • Close to series capacitors, SSR studies: • Are more complex • Take more time to perform • Often find more than one type of issue • May show mitigation damping controls are insufficient • May require controller re-design or extensive R&D by the manufacturer

  10. References • South Texas SSR Event, presented to ROShttp://www.ercot.com/content/wcm/key_documents_lists/139265/10._South_Texas_SSR_ERCOT_ROS_May_2018_rev1.pdf • Challenges Locating Near Series Capacitors, presented to RPGhttp://www.ercot.com/content/wcm/key_documents_lists/108892/ERCOT_Building_Near_Series_Capacitors.pptx

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