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c i f i c a DIgSILENT Pacific P Power system engineering and - PowerPoint PPT Presentation

Jun 20, 2023 •205 likes •493 views

c i f i c a DIgSILENT Pacific P Power system engineering and software T N Two hot topics System strength and the 5.3.9 process E Jennifer Crisp L DIgSILENT Pacific February 2020 I S g I D c i f i c a System strength

  1. c i f i c a DIgSILENT Pacific P Power system engineering and software T N Two hot topics System strength and the 5.3.9 process E Jennifer Crisp L DIgSILENT Pacific February 2020 I S g I D

  2. c i f i c a System strength – 3 messages P • System strength is influenced by fault level, and affects voltage stability T N • It has become a major roadblock to orderly transition of generation to low carbon technologies E • The Rules around this need an urgent re-think L I S g I 2 D

  3. c i f i c a Low fault level = weak grid = low system strength P T N 2020 2010 E 2030 1990 2040 L 1960 I Synchronous generators contribute 3 x fault level of same sized S inverter-based generators Fault level also varies by g Location • Synchronous generation dispatch • I Network outages • 7 D

  4. c i f i c a System strength in the Rules P T N E Generators pay L I Minimum System Strength S g NSPs pay I 8 D

  5. c i f i c a System strength in the Rules P New or altered generators • must mitigate their adverse T Minimum system strength bar system strength impact becomes the baseline for studies N Impact on the power system • or other generators E Creates a queuing • Generators pay arrangement L I Minimum System Strength S g NSPs pay I 9 D

  6. c i f i c a Why is this a big deal? Its all about stability! P X = 0.500 s 1.09 Slower response [p.u.] 1.07 T as fault level Increases 1.05 3.496 s Y = 1.045 p.u. 1.045 p.u. 1.03 1.988 s N 1.045 p.u. Less stable as 0.936 s 1.045 p.u. 1.01 fault level decreases 0.99 0.00 2.00 4.00 6.00 8.00 [s] 10.0 E POC: Strong Grid, SCR = 10, connection point voltage POC: Medium Grid, SCR = 5, connection point voltage POC: Weak Grid, SCR = 3, connection point voltage 0.60 L Less reactive power 0.40 power required 0.20 I as fault level decreases 0.00 for same voltage change S -0.20 -0.40 0.00 2.00 4.00 6.00 8.00 [s] 10.0 g Reactive Power: Strong Grid, SCR = 10, reactive power in pu Reactive Power: Medium Grid, SCR = 5, reactive power in pu Reactive Power: Weak Grid, SCR = 3, reactive power in pu I 10 D

  7. c i f i c a Synchronous generators are not immune P T Damping is lower as fault level reduces N E L I S g I 11 D

  8. c i f i c a Oscillations observed (from USA – similar here) P 4 Hz oscillation on a wind farm T N 7 Hz oscillation on a solar farm E L I S g I Source: Lingling Fan SETO Modelling conference 2019, USF 13 D

  9. c i f i c a What does this mean for technical design? P • NER technical standards favour super- fast responses……. T • But response depends on fault level • A fast response for the ‘typical’ fault level at a connection point may be N unstable if fault level reduces for a network outage • Over time, synchronous plant may retire, reducing the fault level E • Over time the response of voltage control systems speeds up L • As you add more inverter-based plant to the same area, stability declines on existing plant, and new plant are at risk I • Last minute system strength impacts S • Parallel processing leading to over designed synchronous condensers g I 14 D

  10. c i f i c a Impacts of low system strength P • 3 generators in Queensland currently constrained by system strength (more than 12 months) T • New connections in North Queensland stalled N • 5 generators in Victoria/NSW currently constrained by system strength – down to ½ capacity since September 2019 E • 5 NSW/Vic generators in commissioning stalled – constrained at current hold point level L • Many more generators near completion unable to register and connect in West Murray area I • CEC reports $6.28 billion in investments threatened S • Investors are rattled: CEC reports 28 projects were approved in 2019 ($4.5 billion) down from 51 projects in 2018 ($10.7 billion) g • Recent DIgSILENT analysis identified system strength as key barriers to new entry (other barriers being MLFs and congestion) I 15 D

  11. c i f i c a What needs to happen next? P • Technical solution involves coordinated retuning of control settings of existing plant (first step) T • This would minimise the cost of N • Mitigating existing system strength problems • Connecting new generation E • Non-compliances of existing generation L • Recent Rule changes hinder the process of changing control settings • Especially changes to clause 5.3.9 (next topic) I S • Connection Applicants and their consultants need access to the wide area EMT models g • Can’t propose settings to fix what you can’t model. I 16 D

  12. c i f i c a Other Rule factors P • System strength Rules create a queuing process T • Leads to inefficient outcomes, expensive solutions – not consistent with NEO • Sequential connections assessment – significantly delays connection N • Some aspects of the technical standards need work, especially S5.2.5.13 • Faster response is not better E • Need a better way of • Grouping connections L • Optimising controls • Optimising network development I • RIT-T process is too slow for renewables S • System strength impact assessment guidelines needs work • Process for identifying a system strength shortfall needs to be reviewed – clearly didn’t g work for Victoria’s West Murray region • North Queensland as a problem too – that is hindering investment – but doesn’t identify a shortfall I • Preliminary impact assessment does not work 17 D

  13. c i f i c a P T N E L 5.3.9 Process – changes to generating systems I S g I 18 D

  14. c i f i c a 5.3.9 Three messages P • Recent changes to the 5.3.9 process, and associated policies, have added T layers of complexity, time and cost N • The changes also increase the technical risks to the operation of the NEM • Potentially detrimental to power system security and cost of supply to E customers L • Streamlining is required, including changes to the Rules I S g I 19 D

  15. c i f i c a Changes to generating systems P Plan, Decom- Design & mission construct • Clause 5.3.9 of the NER applies to a Generator wishing to alter a connected generating plant T • Applies where • there are alterations to a connected plant N • plant not yet connected, but generator performance standards previously accepted Upgrade Commission E • And will • affect performance of the generating system relative to any technical requirements of S5.2.5, S5.2.6, S5.2.7, S5.2.8 or L Operate compliantly • have an adverse system strength impact (in AEMO’s opinion) or I S • Adversely affect network capability, power system security, quality or reliability of supply, inter-regional power transfer capability or use of network by another Network User g • Present day technical requirements apply • Affected performance standards depends on what is altered. I 20 D

  16. c i f i c a Other relevant changes to Rules : system strength P • System strength: T • NSP must undertake a system strength impact assessment for N each proposed alteration to a generating system to which clause 5.3.9 applies (5.3.4B) E • If the assessment indicates an L adverse system strength impact , either: I • NSP undertakes works at S generator’s cost or • Generator proposes a remediation g scheme or • Both (5.3.4B (e) and (f)) I 21 D

  17. c i f i c a Changes to negotiation framework for technical rules P • Negotiated access standards (5.3.4A(b1)) T • As close as practicable to automatic access standard • Having regard for N • Need to protect plant from damage • Power system conditions at the connection location • Commercial and technical feasibility E • Automatic standards have increased (especially voltage ride through, L response to disturbances, voltage/reactive control systems) • Compliance assessment is much more time consuming and onerous than earlier technical standards I S • Minimum negotiated standard permitted is (5.3.4A(1A)): • no less onerous than the performance standard that corresponds to the technical g requirement that is affected by the alteration to the generating system I 22 D

  18. c i f i c a Additional requirements for connection P • Modelling: • PSCAD models required – NEW • PSS/e models may need to be updated (additional model validation T requirements) • PSS/e Model acceptance tests • Benchmarking of PSS/e and PSCAD models - NEW N • Functional block diagrams and source code • Model validation (R2) report (NEW for PSCAD) • Releasable user guide (NEW for PSCAD) E • Power system datasheets • Performance standards: L • GPS into latest format • Connection studies (NEW technical standards) • Voltage control strategy document (NEW) I • Single line diagrams (various) S • Protection and control scheme details • Generating system capability curve g • System Strength Impact assessment • Preliminary/ Final impact assessment I • Remediation scheme 23 D

  19. c i f i c a Additional requirements for commissioning P • AEMO has published templates T for commissioning of synchronous and asynchronous N plant • Greater emphasis on overlays of E measurement with PSS/e models • Hold points can be much L slower/more onerous (NSP dependent) I S g I 24 D

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