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Solectria Smart Inverters, Effective Grounding, and how to work with the Utility

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Presentation focused on educating solar developers, engineers, and utilities to the benefits of adding solar to the power grid. With some added protection, power factor correction, and remote shutdown capabilities PV installers are now able to interconnect on more distributed generation that was originally thought to be unsuitable.

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Solectria Smart Inverters, Effective Grounding, and how to work with the Utility

  1. 1. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Being Good Citizens of the Grid Claude Colp Applications Engineer Claude.colp@solectria.com @ClaudeColp
  2. 2. Introduction 1. Company Overview 2. Relays 27, 59, 81, ect. 3. Effective Grounding 4. Power curtailment 5. Power Factor 6. Reactive power support 7. Solectria’ s work at ESIF 8. Reactive power support Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Solectria Renewables Lawrence, MA
  3. 3. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Company Overview
  4. 4. 25 Year Development History • Inverter power stage technology developed over 25 years of automotive and military applications • Proven reliability in harsh conditions Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Efficient Powerful Reliable Rugged Commercial, Utility-Scale, and Residential PV Inverters Compact Low Cost EV Drives
  5. 5. Solectria History Solectria divests vehicle products to Azure Dynamics Original 10kW UL Listed Solectria Corporation Founded Introduced the SGI 500XTM & SGI 750XTM External Transformer 1989 2005 2006 2007 2008 2009 2010 2011 2012 Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com 60/82/95KW UL Listed SolrenView Web Monitoring Introduced Capacity Expansion to 200MW PVI 60/77/90KW UL Listed PVI 13-15KW UL Listed PVI 3000-5300 Introduced MSS Introduced Capacity Expansion to 800MW Disconnecting String Combiners Introduced PVI 3800-7600TL, PVI 14-28TL, 3-phase transformerless inverters SGI 500XT transformerless 600V DC inverter introduced 2013 2014 1Ph transformerless inverters Introduced SGI 500 Premium Efficiency model with 97.5% CEC efficiency – highest in the industry Capacity Expansion to 350MW Introduced PVI 50/60/75/85/100KW & Premium Efficiency Models • 1989 – Solectria Corporation founded • 2005 – Solectria Corp. EV division sold to Azure Dynamics • 2005 – Solectria Renewables founded • 2014 – Solectria became wholly owned subsidiary of Yaskawa Electric Solectria Renewables Founded SGI Series UL Listed New SolrenView GUI Introduced Yaskawa Electric Acquires Solectria Renewables as wholly owned subsidiary ARCCOM (AFDI String Combiner) Introduction
  6. 6. Yaskawa and Solectria Yaskawa Electric Corp: • $3.6 billion Japanese firm focused on motor drives, automation controls and other electrical components • Company founded in 1915 • 5th largest Japanese inverter supplier, but no U.S. presence • Global leader in quality • Manufacturing locations in strategic PV markets • Track record for technological advancement and leadership Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  7. 7. Yaskawa and Solectria So what does this mean for our customers?  Immediately enhanced bankability  Warranty backing by bigger company  Solectria is 100% wholly owned subsidiary  Same team in place as before (sales, marketing, customer services, executives)  Same manufacturing locations and product offerings  Potential for new market entry in the future  Access to world class quality systems Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  8. 8. 2014 Company Highlights • Introduction of three-phase string inverters • Introduction of ARCCOM arc fault detection and rapid shutdown combiner boxes for 600VDC and 1000VDC central inverters • Introduction of SGI 500XTM and SGI 750XTM • Acquisition of Solectria Renewables by Yaskawa Electric Corp. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  9. 9. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Protective Relaying
  10. 10. (Digital) Protective Relays “Microprocessor based devices that that control PV plant in response to voltage and current measurement” USED WITH: Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com … Interconnection Breaker … Instrument Transformers Potential Transformers (PTs) … for measuring Voltage Current Transformers (CTs) … for measuring Current …Sometimes Uninterruptible Power Supply (UPS)… for Powering Relay when grid goes down (not required in all systems) “I thought inverters had voltage/frequency trip setpoints??!!  They do. Required when utility desires Additional or Redundant protection Made by companies like SEL, ABB, Cooper, GE, …
  11. 11. ANSI Device Numbers “Standard numbers used by utilities/relay companies to indicate protective function” Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com From PVI 50-100 Installation Manual
  12. 12. Example One Line …Showing Protective Relay w/ ANSI Device Numbers Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  13. 13. Utility Control What is SCADA? Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com “Supervisory Control and Data Acquisition” = Control and Monitoring What would utility want to control?  On/Off (Remote shut down)  Ramp rate  Real Power/Reactive Power/PF How is this implemented?  Control of Interconnection Breaker  24V Remote Shutdown  Shunt Trip  Modbus RTU, Modbus TCP, DNP3 Utility usually interfaces with inverters through RTU’s, Protective Relays, Plant Controller
  14. 14. Example One Line …Showing the pieces INVERTERS INVERTERS INVERTERS Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com I
  15. 15. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Effective Grounding of PV inverters
  16. 16. Non-Grounded Synchronous DG Distribution CB COLOPSEEND Va = Vb = Vc = 100% Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Feeder Load Vb = Vc = 173% SLG Fault Sync. Gen. Consider an islanded operation where the grid is disconnected and a single line to ground fault is applied to the island. Generator neutral shift generates the over-voltages on unfaulted phases. Single phase loads can be damaged from the overvoltage.
  17. 17. Solidly Grounding Synchronous DG Distribution CB Va = Vb = Vc = 100% Grounding the generator neutral prevents over-voltages on unfaulted phases. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Feeder Load COLOPSEEND SLG Fault Sync. Gen. Vb = Vc = 100% Effective Grounding allows 125% over-voltage and impedance grounding (for protection relay coordination) 푋0 푋1 < 3, 푅0 푋1 < 1 Ref: IEEE Std. 142, IEEE Std. C62.92 series
  18. 18. Does same happen with PV inverters? Distribution CB Va = Vb = Vc = 100% Even without the inverter neutral grounding (3-wire connection), over-voltage will not be generated if the load is predominantly wye-connected. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Feeder Load COLOPSEEND SLG Fault PV Inverter Vb = Vc = 100% In contrast to the synchronous generator, a PV Inverter is a current source and no overvoltage will be generated due to the neutral shifting. “… When the inverter-based DG is isolated from the utility voltage source, there is no derived neutral shift.” - Dr. Michael Ropp, 39th Annual Western Protective Relay Conference, Oct. 2012.
  19. 19. PV inverter with pure delta loads Distribution CB COLOPSEEND Va = Vb = Vc = 100% PV Inverter Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Feeder Load Vb = Vc = 173% SLG Fault Solectria’s simulation results showed a negligible voltage rise in unfaulted phases with 50% delta load and 50% wye grounded loads. With 80% delta-connected load, phase voltages went up to 120%, which is still less than the maximum over-voltage with the effective grounding. (125%) In practical cases, most of the loads will be wye grounded in 3-phase 4-wire system.
  20. 20. Effective Grounding  Several utilities require effective grounding by meeting X0/X1 ratio Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com 1.5 < X0/X1 < 2.5 NGRID, HECO, XCEL, PEPCO, BGE, Indianapolis… Some utilities use separate guidelines for inverter based distribution generation(DG) which makes more sense as the inverter characteristics is quite different from the rotating machine type generators XDG0 = 0.6*Zbase +/- 10% GMP, Hydro One…
  21. 21. Suggested Design Practice Case 1. PV plant effective grounding with one or multiple inverters (universal solution) Grounding Bank 51G Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com  Minimal hardware and installation cost  Need to coordinate with the main circuit breaker  Can be used with any medium voltage transformer configuration
  22. 22. Effective Grounding PVI 3ɸ-String Inverters  Require grounding transformer for effective grounding,  Zig-Zag or Yg-Δ Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  23. 23. Grounding bank (transformer)  A grounding bank is a small special transformer configured in Zig-Zag or Delta-Wye.  A grounding bank is external to PV inverters and provides effective grounding, so Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com that it does not impact the inverters transformer life.  A single grounding bank can provide effective grounding for a large PV plant, which minimizes the installation cost.  For a SGI 500kW inverter installed at 480V distribution feeder, grounding bank cost can be several $K. PV Inverter Grounding bank 51G
  24. 24. Suggested Design Practice Case 2. PV plant effective grounding with grounding inductor and a dedicated wye-delta MV Transformer Grounding inductor 51G Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com  Can be used with a wye-delta medium voltage transformer only  Can be effectively grounded with a grounding bank also  Minimal hardware and installation cost
  25. 25. Effective Grounding Summary  Most 3-phase 4-wire systems support single phase loads, which puts the effective grounding requirement for PV inverters in question.  Many utilities request effective grounding with a controlled impedance for relay protection coordination.  Solectria provides impedance tables for all commercial and utility scale PV inverters to help customers design an effectively grounded PV system.  Effective grounding using Zig-Zag transformer is a universal solution for ungrounded DG.  Many Solectria inverters have an internal wye-delta isolation transformer with a neutral connection which can be used to provide effective grounding. When used, neutral over-current protection is strongly recommended. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  26. 26. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Power Curtailment
  27. 27. Power Curtailment 80kW  50kW  80kW 90 80 70 60 50 40 Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com 30 50 60 70 80 90 100 Power in KW percentage Pcmd Pout
  28. 28. Advantages of Power Curtailment Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com • 100kW interconnection Limit PLC 700k W 750k W ~50k W Monday through Friday
  29. 29. Advantages of Power Curtailment • 100kW interconnection Limit Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com PLC 170k W 70kW ~100kW Saturday and Sunday 23% limit
  30. 30. Case Study – Xcel Energy System Size 30 MW Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Product: 504, PVI 82KW – SCADA controlled, VAR supports Modules Amonix Installer Amonix, Cogentrix Location Alamosa, CO
  31. 31. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Reactive Power
  32. 32. Inverter Capacity for VARs Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com • Inverter and AC interconnection have to be sized to carry both real and reactive current Example: 500kVA @ 0.95 PF 475 kW 156 kVAr
  33. 33. Inverter Capacity for VARs Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com • Inverter and AC interconnection have to be sized to carry both real and reactive current Example: 500kVA @ 0.95 PF 475 kW 475 kW 156 kVAr
  34. 34. Inverter Capacity Allocation for VARs Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com • Inverter and AC interconnection have to be sized to carry both real and reactive current Example: 500kVA @ 0.95 PF 475 kW 156 kVAr 475 kW
  35. 35. Inverter Capacity Allocation for VARs 0.8 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 0 0.2 0.4 0.6 0.8 1 Q Reactive p.u. P Active p.u. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com  Power factor control = +/- 0.8 (+/- 0.95 prefered)  Maximum reactive power control = 60%  May require power curtailment for reactive power control  May conflict with the islanding detection
  36. 36. VAR support (remote utility option) 1000 800 600 400 200 0 -720 -630 -540 -450 -360 -270 -180 -90 0 90 180 270 360 450 540 630 720 -200 -400 -600 -800 -1000 voltage current power (rms) real power (rms) Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com • PPA owned (“in front of the fence”) o UL1741 enforces a PF > 0.95
  37. 37. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Reactive Power Control The waveform shows instantaneous transient response of the inverter output current (red) from full inductive to full capacitive.
  38. 38. DNP3 Compliant Smart Grid Inverters Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  39. 39. High Penetration Scenario Example: Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com • 1.7 MW site in Cedarville NJ • 4.7 miles from substation 12kV feeder, 6MW mid-day load • Concerns of local overvoltage • Utility has closed circuit for more PV 0.5 MW 1.7 MW
  40. 40. Overvoltage Concerns Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com 3.0% of points exceed +5% limit
  41. 41. The effect of reactive power on distribution lines Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com VAR Generation PCC voltage is being pushed up. VAR Absorption PCC voltage is being pulled down.
  42. 42. Example: PF control Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com • Feeder could be reopened for PV after PF adjustment to 0.97 • “Flicker” Mitigation (cloud induced voltage transients) < 0.1% of points exceed 5% limit
  43. 43. Benefit to Utility Example: Volt-VAR control • Reduced wear out of electromechanical voltage regulators • Flatter voltage profile overall Possible additional Voltage Regulator Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Baseline – No PV Inverter Volt-Var Control 20% PV Penetration action
  44. 44. Increasing Hosting Capacity with Smart Inverters Without Volt/var Control Volt/var Control ANSI voltage limit Increasing penetration (kW) Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Matthew Rylander 5000 cases shown Each point = highest primary voltage ANSI voltage limit 160% increase in hosting capacity 60% increase in hosting capacity Maximum Feeder Voltage (pu) Maximum Feeder Voltages (pu) Increasing penetration (kW) No observable violations regardless of size/location Possible violations based upon size/location Observable violations occur regardless of size/location PV Hosting Capacity (kW) Without Volt/var With Volt/var Primary Voltage Deviation 1st violation 938 >2500 50% scenarios with violation 1323 >2500 All scenarios with violation 1673 >2500 Primary Over Voltage 1st violation 540 880 50% scenarios with violation 871 1464 All scenarios with violation 1173 2418 Slide courtesy of Matthew Rylander, EPRI
  45. 45. Solectria’s Work in this Field Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  46. 46. o Smart Grid Ready Inverter Development  Implement and test grid support functions on existing Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com commercial and utility scale inverters.  Add DNP3 communication capability on to the existing inverters  Hardware reliability enhancement and efficiency increase  Cost Reduction o Plant Master Controller Development  Support smart grid inverters with the latest DNP3 protocol  Plant level supervisory controller with customizable system integration capability  Secondary protection and preventive maintenance
  47. 47. Product Testing • The Energy System Integration Facility (ESIF) at NREL was chosen to test the SGI 500 features due to its advanced capabilities • The EPRI facility in Knoxville, TN was chosen to test the PVI 100KW for their expertise in inverter testing. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com NREL Test Setup Size PV simulator 1MW Grid Simulator 1.2MW Output Power 400kW Reactive Power + 300kvar
  48. 48. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Volt-var testing at ESIF Test # EUT Terminal Voltage EUT Reactive Power Output Ramp Time (s) Time Window (s) Reversio n Time (s) PASS /FAIL Volt % kvar % Max available var Test 2 432 90 300 100 5 60 Never time out p 475.2 99 0 100 484.8 101 0 100 518.4 108 -309 100
  49. 49. Balanced LVRT/HVRT at ESIF Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com 10% Balanced sag for 120 cycles, passive LVRT Balanced voltage swell of 118%; active ride through trip test condition
  50. 50. Unbalanced LVRT (IEEE P1668) at ESIF • 89% of Faults are unbalanced faults Balanced Sag Single phase sag Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com ZVRT for 120 cycles
  51. 51. Frequency/Watt at ESIF Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  52. 52. Watts, Hz and Volts • Utilities like their “Volts” and “Hz” to stay within boundaries. • When generation is High (+Watts) system wide frequency rises (+Hz)  Functions that control “Watts” depending on “Hz”, such as Frequency-Watt, are essential for being a good citizen on the grid. • An increase in generation (+Watts) results in a local increase in Voltage (+Volts)  Functions that control “Watts” depending on ”Volts”, such as Volt- Watt, can be useful to regulate local voltage when the vars are exhausted. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com
  53. 53. Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com Questions?
  54. 54. Thank You! One size doesn’t fit all, But one company does Built for the real world Solectria Renewables / Company Confidential © 2014 www.solectria.com

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