2014 PV Distribution System Modeling Workshop: Pro-active, high penetration PV studies on distribution systems: Jonathan Flinn, DNV GL
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2014 PV Distribution System Modeling Workshop: Pro-active, high penetration PV studies on distribution systems: Jonathan Flinn, DNV GL

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2014 PV Distribution System Modeling Workshop: Pro-active, high penetration PV studies on distribution systems: Jonathan Flinn, DNV GL

2014 PV Distribution System Modeling Workshop: Pro-active, high penetration PV studies on distribution systems: Jonathan Flinn, DNV GL

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    2014 PV Distribution System Modeling Workshop: Pro-active, high penetration PV studies on distribution systems: Jonathan Flinn, DNV GL 2014 PV Distribution System Modeling Workshop: Pro-active, high penetration PV studies on distribution systems: Jonathan Flinn, DNV GL Presentation Transcript

    • DNV GL © 2013 May 6th 2014 SAFER, SMARTER, GREENERDNV GL © 2013 May 6th 2014 Jonathan Flinn Pro-Active, High Penetration PV Analysis on Distribution Systems 1 PV Distribution System Modeling Workshop Santa Clara, CA
    • DNV GL © 2013 May 6th 2014 Contents  Introduction  Objectives of Analyses  Overview of Approach  Technical Criteria  Analysis in SynerGEE  Modeling Advanced Inverter Functions in SynerGEE  Conclusion 2
    • DNV GL © 2013 May 6th 2014 Introduction – DNV GL  Merger of brands, consolidation of experience and expertise 3
    • DNV GL © 2013 May 6th 2014 An energy technology powerhouse 4 Offshore wind Strong expertise in offshore wind, its support vessels and connection to the electricity grid Innovation Strategic research in energy storage, smart grids and super grids; developments of new standards through joint industry projects Testing Global leader in testing, inspecting and certifying high- power and renewable energy equipment with world class laboratories Expert advice In onshore and offshore wind power, solar, smart grids, super grids, infrastructure resilience, energy markets, regulations and use Power player A strong player across the value chain: renewable and conventional power generation, transmission & distribution and sustainable energy use
    • DNV GL © 2013 May 6th 2014 Introduction – Jonathan Flinn  MEng Mechanical Engineering with Aeronautics, University of Strathclyde, 2004  MSc Safety, Risk and Reliability Engineering, Heriot-Watt University, 2005  9 years in DNV GL  Worked with pipelines, wind energy, arctic operations, wave and tidal energy  Worked in transmission and distribution since 2011 5
    • DNV GL © 2013 May 6th 2014 Introduction – Pro-Active Approach  Developed in co-operation with HECO  Aim to streamline PV interconnection process  Objectives: – Improve PV interconnection process – Identify limits on a circuit-specific basis – Facilitate efficient network planning – Identification of limits in advance – Identify existing risks – Compare limits with existing PV penetrations – Identify future limits to PV integration – Run hypothetical future PV scenarios up to high PV penetrations – Identify appropriate mitigation measures – Developed from list of potential mitigation measures 6
    • DNV GL © 2013 May 6th 2014 CA Rule 21 7 Complete application received Screen 1: Connection to distribution system? Screen 2: Connection to network Screen 3: Export power causes reverse flow at voltage regulation devices Screen 4: Is the aggregate generating facility on the line section <=15% of line section peak load Screen 5: Is voltage flicker and/or voltage drop due to project within IEEE 519 limits Screen 6: DG <= 10kW Screen 7: Inverter-based DG <= 250kW meets IEEE 1547 & UL 1741 Screen 8: SCCR within acceptable limits Screen 9: Interconnection compatible with line configuration Perform Supplemental Review Does not qualify for interconnection under Rule 21 Does supplemental review determine requirements? Company provides the cost estimate and schedule for IRS to determine requirements Generating Facility qualifies for interconnection subject to requirements, if any, determined by supplemental review Generating Facility qualifies for Simplified Interconnection no no no yes yes no no yes yes yes yes no no no no yes yes yes yes no
    • DNV GL © 2013 May 6th 2014 CA Rule 21 8 Complete application received Screen 1: Connection to distribution system? Screen 2: Connection to network Screen 3: Export power causes reverse flow at voltage regulation devices Screen 4: Is the aggregate generating facility on the line section <=15% of line section peak load Screen 5: Is voltage flicker and/or voltage drop due to project within IEEE 519 limits Screen 6: DG <= 10kW Screen 7: Inverter-based DG <= 250kW meets IEEE 1547 & UL 1741 Screen 8: SCCR within acceptable limits Screen 9: Interconnection compatible with line configuration Perform Supplemental Review Does not qualify for interconnection under Rule 21 Does supplemental review determine requirements? Company provides the cost estimate and schedule for IRS to determine requirements Generating Facility qualifies for interconnection subject to requirements, if any, determined by supplemental review Generating Facility qualifies for Simplified Interconnection no no no yes yes no no yes yes yes yes no no no no yes yes yes yes no Pro-active approach identifies at which PV penetrations this will occur for each feeder/transformer
    • DNV GL © 2013 May 6th 2014 CA Rule 21 9 Complete application received Screen 1: Connection to distribution system? Screen 2: Connection to network Screen 3: Export power causes reverse flow at voltage regulation devices Screen 4: Is the aggregate generating facility on the line section <=15% of line section peak load Screen 5: Is voltage flicker and/or voltage drop due to project within IEEE 519 limits Screen 6: DG <= 10kW Screen 7: Inverter-based DG <= 250kW meets IEEE 1547 & UL 1741 Screen 8: SCCR within acceptable limits Screen 9: Interconnection compatible with line configuration Perform Supplemental Review Does not qualify for interconnection under Rule 21 Does supplemental review determine requirements? Company provides the cost estimate and schedule for IRS to determine requirements Generating Facility qualifies for interconnection subject to requirements, if any, determined by supplemental review Generating Facility qualifies for Simplified Interconnection no no no yes yes no no yes yes yes yes no no no no yes yes yes yes no Pro-active approach identifies specific limitations for each feeder/cluster due to different criteria (thermal loading, voltage violations, etc.),
    • DNV GL © 2013 May 6th 2014 CA Rule 21 10 Complete application received Screen 1: Connection to distribution system? Screen 2: Connection to network Screen 3: Export power causes reverse flow at voltage regulation devices Screen 4: Is the aggregate generating facility on the line section <=15% of line section peak load Screen 5: Is voltage flicker and/or voltage drop due to project within IEEE 519 limits Screen 6: DG <= 10kW Screen 7: Inverter-based DG <= 250kW meets IEEE 1547 & UL 1741 Screen 8: SCCR within acceptable limits Screen 9: Interconnection compatible with line configuration Perform Supplemental Review Does not qualify for interconnection under Rule 21 Does supplemental review determine requirements? Company provides the cost estimate and schedule for IRS to determine requirements Generating Facility qualifies for interconnection subject to requirements, if any, determined by supplemental review Generating Facility qualifies for Simplified Interconnection no no no yes yes no no yes yes yes yes no no no no yes yes yes yes no Identification of areas of risk/interest for the feeder, allows focus of analysis on circuit- specific issues
    • DNV GL © 2013 May 6th 2014 System Boundaries 11 Example of system boundary One sub-transmission line, plus all connected distribution feeders
    • DNV GL © 2013 May 6th 2014 Analysis Approach  Model load independently of solar – Requires some manipulation of demand data  Find peak and minimum daytime load days  Run analyses with varying penetrations of PV  Use linear interpolation to find technical limits 12
    • DNV GL © 2013 May 6th 2014 Analysis Approach  Use combinations of load profile and PV penetration 13 Load Scenarios 1. Peak Daytime Load Day 2. Minimum Daytime Load Day PV Penetration Scenarios 1. No PV 2. Existing PV 3. Existing + Queued PV 4. PV = 15% of Peak Load 5. PV = 30% of Peak Load 6. PV = 50% of Peak Load 7. PV = 75% of Peak Load 8. PV = 100% of Peak Load 9. PV = 135% of Peak Load
    • DNV GL © 2013 May 6th 2014 Technical Criteria 14 Technical Criterion Limit or Trigger Steady-State Voltage V > 1.05 p.u. or V < 0.95 p.u. Thermal Loading Loading > 100% Backfeed Reversal of flow through transformer Fault Current Available fault current exceeds breaker interrupt rating Transient Voltage Voltage change > 3% during step change in PV output Dynamic Voltage Overvoltage / undervoltage due to inverter trips during N-1 Dynamic Frequency Additional load shedding due to inverter trips during N-1 LTC Cycling Increase in LTC operations due to PV operation
    • DNV GL © 2013 May 6th 2014 LTC Cycling Studies  An increase in LTC cycling due to PV is not necessarily a significant problem – If it causes 1 extra operation per week, still very small change  At some point it could become a problem, causing decrease in time between maintenance, and LTC lifetime – Number of increased operations per year can be calculated for each PV penetration, and compared against a limit defined by utility 15 N u m b e r o f E v e n t s Change in Irradiance [W/m2s]
    • DNV GL © 2013 May 6th 2014 LTC Cycling Studies  A reverse effect must also be studied: – PV operation causes reduced current through LTC compared to no-LTC case – Reduced current may increase LTC contact lifetime – This effect reverses past point of backfeed, where increased PV causes increased current – Chart below comes from Kaukesha UZD LTC Technical Manual 16
    • DNV GL © 2013 May 6th 2014 Analysis in SynerGEE – Model Setup  Load and generation on utilization circuits aggregated to distribution transformers  PV modeled as generator in SynerGEE (not negative load) – Necessary for fault analysis – Also allows use of irradiance profiles  Existing generators modeled in existing locations  Hypothetical ‘future’ generators placed by analyst to allow up to 150% PV Penetration 17
    • DNV GL © 2013 May 6th 2014 Analysis in SynerGEE – Recipe Scripts  SynerGEE allows use of automated analysis – Consecutive load flows run using ‘recipe’ commands – Outputs saved to specified location – Ideal for use with 24-hour load profiles  Model Cleanup scripts can be used to make changes between analyses 18
    • DNV GL © 2013 May 6th 2014 Analysis in SynerGEE - Solver  SynerGEE add-on which further increases flexibility  Allows changes to be made to model (more than Recipe or ModClean)  Compiles and post-processes results  Requires some basic programming skills  Flexibility is useful in Advanced Inverter Modeling 19
    • DNV GL © 2013 May 6th 2014 Mitigation of PV Impacts Mitigant Backfeed Loading Voltage LTC Cycling Fault Current Dynamics Transients Energy Storage X X X X Curtailment X X X X Inverter power factor control X Inverter disconnection and re-closing control X X Equipment upgrades X X X X 20
    • DNV GL © 2013 May 6th 2014 Energy Storage 21 Load > PV: Load is fed by grid PV > Load: Load is fed by PV PV > Load: Excess PV charges battery Load > PV: Load is fed by battery  Mitigates: Backfeed Violations, Voltage Violations  Energy storage systems can be used to prevent backfeed from occurring  Simple model in SynerGEE is to calculate total reverse power flow and energy  New battery model in SynerGEE 5.1 will allow individual batteries to be charged and discharged
    • DNV GL © 2013 May 6th 2014 Curtailments  Curtailment is a smart inverter function  Allows utility to either: – Reduce output from generator to solve problem – Disconnect generator completely  Cost to utility is cost of ‘lost’ energy to generator  Simple model in SynerGEE is same as for energy storage: – Calculate total energy that would be curtailed to prevent backfeed 22
    • DNV GL © 2013 May 6th 2014 Inverter Power Factor Control  Increasing or decreasing VAR output from inverter can regulate local voltage 23  Single time-step can easily be modified in SynerGEE  Automation can run multiple time-steps consecutively and identify local voltage problems using Solver: Run load flow Voltage violation? Reduce inverter power factor Move to next time- step No Yes  Complexity of process can be increased  In practice staged reduction in power factor will be necessary to prevent over-correction
    • DNV GL © 2013 May 6th 2014 Inverter Disconnection and Re-Closing control  When trips and transient events happen, loss and return of all generators at once can cause problems due to time delay on LTC  Smart inverters provide options: – Ramp up of output – Variable trip settings – Variable re-closing settings 24
    • DNV GL © 2013 May 6th 2014 Comparison of Mitigation Techniques 25
    • DNV GL © 2013 May 6th 2014 Conclusion  Pro-Active Approach can help to streamline PV interconnection process – Can also help to plan equipment upgrades  Analysis performed in SynerGEE allows flexibility to modify process – Also allows automation of analysis and post-processing  Flexibility of SynerGEE also allows approximation of advanced and smart inverter characteristics – Integration with energy storage – Curtailment – Power factor control – Output ramping 26
    • DNV GL © 2013 May 6th 2014 SAFER, SMARTER, GREENER www.dnvgl.com Thank you for your attention 27 Jonathan Flinn Jonathan.flinn@dnvgl.com (925) 327-3044