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2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase
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2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase

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2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase

2014 PV Distribution System Modeling Workshop: Capabilities of Advanced Inverter: John Berdner, Enphase

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  • 1. Capabilities of Advanced Inverters John Berdner Director of Worldwide Standards
  • 2. Overview of Presentation | © 2013 Enphase Energy, Inc. | Confidential2 Nomenclature for Advanced Inverters and Functions Ride through Functions Voltage Ride Through, Frequency Ride Through Real Power Control Functions Frequency/Watt, Volt/Watt Reactive Power Control Functions Volt/VAr Communications Commanded Operation, Autonomous Profiles Communication issues
  • 3. Nomenclature | © 2013 Enphase Energy, Inc. | Confidential3 Need to be careful about using anthropomorphic terms… - What comes after “advanced” inverters? - What comes after “smart” Inverters ? Suggestion: Inverters with real and reactive power control functions EPRI “Common Functions for Smart Inverters, Version 3” An excellent overview of functions / capabilities / issues
  • 4. Ride Through Functions | © 2013 Enphase Energy, Inc. | Confidential4 Historically inverters were programmed to get offline quickly in response to grid voltage or frequency excursions - Existing regulatory structures in the US did not adequately address ride through requirements. - Requirements were written as “must disconnect” not as “must remain connected” - As levels of Distributed Energy Resources (DER) increase this strategy becomes problematic. - Loss of large amounts of DER in advance of load shedding can lead to cascade failure.
  • 5. L/H Voltage Ride Through | © 2013 Enphase Energy, Inc. | Confidential5 EPRI Common Functions For Smart Inverters V3, page 14-2
  • 6. Voltage Ride Through Issues | © 2013 Enphase Energy, Inc. | Confidential6 Inverters can provide controlled full current down to near zero voltage for extended periods of time but… there are some issues. - Very low voltages are normally seen in response to feeder faults and additional fault current may be undesirable. - At very low voltages, frequency measurement signal to noise ratio deteriorates - Very low voltage operation of inverters may increase power supply costs and complexity Focus of requirements to date has been on what happens at beginning of event. Of equal import is what happens when / how the DER returns to service.
  • 7. L/H Voltage Ride Through | © 2013 Enphase Energy, Inc. | Confidential7 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 0.01 0.1 1 10 100 1000 Voltage(perUnit) time (seconds) Operating Regions - Must Remain Connected OV_MSC UV_MSC Normal Operation Region High (NORH) Undervoltage Region 2MSC - UV2MSC Undervoltage Region 1 - UV1MSC Overvoltage Region 1 - (OV1MSC)
  • 8. Frequency Ride Through | © 2013 Enphase Energy, Inc. | Confidential8 EPRI Common Functions For Smart Inverters V3, page 15-2
  • 9. Frequency Ride Through Issues | © 2013 Enphase Energy, Inc. | Confidential9 Inverters can provide controlled full current down to very low frequencies for extended periods. - Frequency excursion is normally in response to system level events. - Low frequency behavior needs to be coordinated with local load shedding schemes. - Inverters are less sensitive to damage from low frequency operation than rotating machines. During high frequency excursions ride through and Frequency / Watt functions are normally used together. - Real power may be programmed to be at zero before reaching the ride through limits.
  • 10. Real Power Control Functions | © 2013 Enphase Energy, Inc. | Confidential10 Real power control functions modulate real power output in response to changes in Voltage or frequency Typical Real Power Control functions include: - Volt / Watt - Reduces real power output with rising voltage - May be possible to increase power with lower voltages if storage is present in the system - Can be used with ramp rate control on initial startup. - Frequency / Watt - Reduces real power output with rising frequency - May be possible to increase power with lower voltages if storage is present in the system - Can be used with HF ride through for more stability
  • 11. Example: Real Power Control Function | © 2013 Enphase Energy, Inc. | Confidential11 Example Volt Watt Diagram Parameters - Dead band (Vnom – V2) = no power reduction - Response Gradient %P/Volt = (P3-P2)/(V3/V2) - Other considerations – Response time, averaging intervals, intentional delay
  • 12. Reactive Power Control Functions | © 2013 Enphase Energy, Inc. | Confidential12 Reactive power control functions modulate reactive power output in response to changes in Voltage, or real power output. Typical Reactive Power Control functions include: - Volt / VAr with Watt priority (available VAr or VV11). - Provides VAr support with no reduction in real power - VAr capacity varies inversely with solar resource - Volt / VAr with Var priority (available VAr or VV12). - Provides VAr support and may reduce real power - VAr capacity is independent of solar resource - May require specific Tarriffs or Rates - Watt /Var (not common in the North America)
  • 13. Example: Reactive Power Control Function | © 2013 Enphase Energy, Inc. | Confidential13 Example Volt VAr Diagram Parameters - Dead band (V3 – V2) = no power reduction - Response Gradient %Qa/Volt = (Q4-Q3)/(V4/V4) - Other considerations – Response time, averaging intervals, intentional delay
  • 14. Communication – Commanded Operation | © 2013 Enphase Energy, Inc. | Confidential14 Inverters respond in “near real time” to commands from the utility. Example commanded modes: On/Off (P&Q = 0) Fixed Real Power (may require storage) Maximum Real Power Fixed Power Factor Mode Change – Profile A or Profile B
  • 15. Communication – Autonomous Profiles | © 2013 Enphase Energy, Inc. | Confidential15 High speed SCADA communications is not cost effective for high numbers of smaller systems. Inverters can be pre-programmed with one or more autonomous operating profiles. - Inverters would then continue to operate according to this profile until commanded to do otherwise. - Provides high speed response without need for high speed communications Updates to profiles or changes in operating modes can occur over public IP networks - Customer Network or Cellular Modem (M2M) Mode changes might also be possible over AMI system.
  • 16. Communication – Issues 1 | © 2013 Enphase Energy, Inc. | Confidential16 Cyber Security of communication to DER systems No global standard communication protocols - DNP 3 is one common protocol used by utilities. - Not well suited to control of large numbers of inverters - Not used by all utilities - IEC 61850 Data model may be a common language - Sunspec Mapping to IEC 61850 for inverters - DNP 3 to IEC 61850 for Utilities Response time will be dependent on communication system used Not all systems will receive / respond to commands (Stochastic planning needed)
  • 17. Communication – Issues 2 | © 2013 Enphase Energy, Inc. | Confidential17 Undefined demarcation points for communication protocols - Where are various protocols used ? - Who is responsible for protocol translations ? - DNP 3 to IEC 61850 based protocol - IEC 61850 protocol to inverter specific protocol Undefined commercial issues - Who is responsible for processing commands ? - Inverter manufacturers, system aggregators, system owners - How are ongoing “back end” costs covered ?
  • 18. Questions | © 2013 Enphase Energy, Inc. | Confidential18 Thank you for your attention John Berdner jberdner@enphaseenergy.com

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