Distributed Energy Resources

Transcription

1 Distributed Energy Resources Operational Impacts Jenny Riesz Principal, Operational Analysis & Engineering

2 About AEMO We operate Australia's National Electricity Market and power grid in Australia s eastern and south-eastern seaboard, and the Wholesale Electricity Market and power grid in south-west WA. Both markets supply more than 220 terawatt hours of electricity each year. We also operate retail and wholesale gas markets across south-eastern Australia and Victoria s gas pipeline grid. Collectively NEM & WEM traded over A$20 billion in the last financial year. Ownership 40% Market participants 60% Governments of Australia 2

3 Growth in DER AEMO s forecast for the NEM: Distributed Energy Resources (DER) are growing rapidly The transition to decentralised resources could represent the most significant power system transformation since it was established Rooftop PV Storage 3

4 Context Minimum demand in South Australia: DER generation will soon match entire demand in some NEM regions. Rooftop PV What will this mean for the power system? How do we affordably maintain security and reliability for customers throughout this transition? What actions do we need to take? 4

5 Performance standards Dynamic models Technical challenges Need for review of performance standards for DER to ensure they adequately support system security needs Dynamic models do not generally capture the behavior of DER during disturbances with sufficient accuracy. Focus on these two in this presentation A suite of technical challenges identified, requiring action to maintain system security for customers. Voltage management Emerging challenges managing transmission & distribution voltages at times of low operational demand Visibility Need for collection of standing data on DER installed for forecasting, system planning, and stability studies VPP management Unmanaged rapid movement of large virtual power plants could cause increased need for frequency control, and system security challenges Orchestration Need for coordination between AEMO and distribution networks in DER dispatch Emergency Frequency Control Schemes System restoration System Strength PV feed in management Emergency Frequency Control Schemes and special protection schemes may no longer operate successfully under high rooftop PV conditions Unmanaged DER operation may interfere with progressive restoration of load during a system restart process Potential for system strength challenges to emerge at the distribution level, affecting DER operation, protection, etc. Need for mechanisms to actively manage and optimise DER generation to maintain dispatch flexibility 5

6 Disturbance ride-through Disturbance ride-through essential for maintaining power system security Problematic DER behaviour identified for: Voltage disturbances Frequency disturbances Voltage phase angle jump (instantaneous phase shift in sinusoidal voltage waveforms) Widespread disconnection of DER during disturbances could lead to system black Must be addressed prior to installation via appropriate performance standards Following slides present case studies and issues identified This is work in progress! Preliminary results only. 6

7 Voltage disturbances

8 3 rd March 2017 Demand in South Australia: Series of faults resulted in the loss of ~610 MW of generation in SA Flows on Heywood interconnector increased to ~918 MW. Estimated that demand reduced ~400 MW Generation by distributed PV: Estimated that distributed PV reduced by ~150 MW (40%) Loss of more PV would have increased flows on Heywood interconnector further. Data from Solar Analytics (~200 distributed PV systems) confirms disconnection of some inverters: Analysis by Naomi Stringer, UNSW Sydney Data from Solar Analytics 8

9 18 th January 2018 Fault on 500 kv network in Victoria ~160 distributed PV sites monitored by Solar Analytics Aggregate distributed PV generation observed to reduce by 28% (~180 MW loss estimated across VIC). Analysis by Naomi Stringer, UNSW Sydney Data from Solar Analytics 9

10 Bench testing of PV inverters Bench testing program Collaboration with UNSW Sydney, funded by ARENA Laboratory conditions Tested 5 inverters so far (preliminary findings) Voltage testing results: Two inverters observed to trip during a short duration voltage sag. Need to clarify in standard. Only 1 inverter performed Volt-Watt response correctly. The other 4 inverters were either too slow, or result in a disconnection. Need to clarify in standard. Bench testing by UNSW Sydney as part of an ARENA-funded collaboration with AEMO, TasNetworks & ElectraNet 10

11 Frequency disturbances

12 Frequency disturbances Frequency disturbances recorded at a primarily residential feeder in Tasmania 13 Aug 2018, 8:43am Estimated PV capacity factor: 21% Possible reduction in PV generation: 48% Frequency falls to below 49Hz over ~5s Active power supplied to the feeder increases suddenly Further investigation underway to determine whether this is due to DER disconnection, and whether this feeder is representative of all Tasmanian PV 25 Aug 2018, 1:11pm Estimated PV capacity factor: 44% Possible reduction in PV generation: 18% Analysis by Shabir Ahmadyar, UNSW Sydney Data from TasNetworks 12

13 Bench testing of PV inverters Laboratory conditions Preliminary frequency testing results: Grid frequency step 50 45Hz (Inv #2) Under frequency ride-through Two inverters observed to trip too quickly on underfrequency. Appears to be a serious non-compliance with AS RoCoF One inverter tripped on RoCoF levels above 0.4Hz/s. RoCoF ride-through not addressed in standard at present Over-frequency droop Inverter trips in t < 50 ms One inverter responds slowly to an over-frequency (~30s) Strictly compliant with the standard, but not useful for assisting with frequency management Bench testing by UNSW Sydney as part of an ARENA-funded collaboration with AEMO, TasNetworks & ElectraNet 13

14 Emergency frequency control DER over-frequency droop response could become essential for system security Few centralised units operating at times of high DER generation inadequate capacity to trip to correct an emergency over-frequency Needs to be adequately fast Required in emergency situations where contingency size exceeds frequency reserves, typically large disturbances, high RoCoF But slow enough to avoid mal-operation (need adequate time to measure a stable grid frequency) Could rapid ramp down of bulk rooftop PV cause distribution voltage issues? And could this lead to widespread PV tripping on under-voltage? Enable mandatory Volt-Var responses to allow DER to assist with local voltage management while responding to frequency? 14

15 Phase angle jump

16 Phase angle jump Observed challenge in California for utility-scale PV Inverter mis-calculates frequency and activates protection Addressed in IEEE (requires ride-through for up to 60 jump) Bench testing indicates this applies for distributed PV inverters in the NEM for voltage phase angle jumps Unclear the degree to which phase angle jump may be visible in the distribution network Examining high speed data Bench testing of distributed PV inverters: (preliminary findings) Voltage phase jump magnitude Inverter 1 Inverter 2 Inverter 3 Inverter 4 Inverter Disconnection Temporary reduction of power injected to grid Temporary reduction of power injected to grid Bench testing by UNSW Sydney as part of an ARENA-funded collaboration with AEMO, TasNetworks & ElectraNet 16

17 High speed data 15 th Feb 2017, 10:34am High speed data recorded at a local distribution feeder in QLD, primarily residential, high levels of distributed PV Several events recorded with high levels of distributed PV operating, and see increase in load post disturbance Further investigation to determine whether this is due to DER disconnection 12 th March 2017, 1:27pm The voltage dip is very shallow. Could be due to phase angle jump. Further investigation underway. Analysis by Shabir Ahmadyar, UNSW Sydney Data from Energy Queensland 17

18 Adaptation of DER standards

19 Possible changes to DER performance standards Voltage Disturbances: Frequency Disturbances: Other: For consultation, implementation to be determined Voltage ride-through Extend as much as possible Multiple voltage disturbances Ride-through requirements for multiple voltage disturbances Frequency ride-through Extend as much as possible RoCoF ride-through Ride-through requirements for RoCoF Phase angle jump Specify ride-through requirements Interoperability Emergency feed-in management, remote querying of device settings, remote changes to settings Volt-Var and Volt-Watt Over-frequency response Coverage Default enablement Determine relative priorities of control schemes Consider smaller deadbands and settings aligned with international standards Momentary cessation Determine appropriate requirements, considering periods with most generation from DER Specify required response times Under-frequency response Require response from already curtailed inverters Specify response times Storage systems move to discharging? Other loads (eg. electric vehicles) Review appropriate coverage, including sizes & types of DER, and consumer loads Compliance Review compliance mechanisms Cyber security Device & architecture properties 19

20 Integrating DER to maximise consumer value DER Workstream Network incentives Data visibility System & Market framework Technical standards & connections Operational process Industry-wide collaboration Workstream objectives Network regulation & pricing facilitate DER and better customer service offerings. Visibility of DER for operational, forecasting, planning, and market (incl settlement) functions. A consistent access regime for all market participants within the confines of customer consent and privacy. Integrate DER into energy, ancillary and reserve markets. Market arrangements recognise non-retailer models, including thirdparty/aggregator concepts. Evolve market arrangement to a distributed market model. Where appropriate, a nationally consistent approach to DER connections and develop DER technical standards. To better understand operational challenges and DER capabilities to inform operational processes and tools. Industry working together to deliver outcomes for consumers Enablers Pilot programs Cyber security Digital & Technology Strategies 20

21 DER represents a significant transition for the electricity industry The impact of DER on power system security must be considered as a priority By identifying challenges early, we can implement the measures required to affordably maintain security and reliability for customers throughout this transition 21