RC-5 2017 Isaacs Electranix MRO Talk · HECO Rooftop PV/load modeling 3. ... PSSE Fast reactive ......
Transcript of RC-5 2017 Isaacs Electranix MRO Talk · HECO Rooftop PV/load modeling 3. ... PSSE Fast reactive ......
Andrew IsaacsVice‐President, Electranix Corporation
2017 Fall Reliability ConferenceOctober 25, 2017
Electranix Corporation
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ELECTRANIX Corporation is an independent specialist engineering company providing services in transmission and distribution studies and simulation, HVDC transmission, FACTS, modeling and simulation tools, training, and renewable energy generation.
(Tutorial?) Outline What is the need for EMT when integrating renewables?
Weak Systems Control interactions SSO
Inverter based generation EMT model requirements Network EMT model requirements Sample of recent EMT work in the US
AEP Routine SSCI studies Texas large system study (round 2) ISONE Validation/Benchmarking HECO Rooftop PV/load modeling
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General limitations as the grid weakens or series caps are present… Conventional transient stability tools may
overestimate stability, or represent protection and control features in insufficient detail
May indicate tripping where none would occur, or indicate no tripping where tripping would occur.
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Transient Stability Tool Limitations:
Transient Stability Tool Limitations:
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Specific Limitations Valid only for 50/60 Hz (or frequencies up to approximately 5 Hz)
Simplified generator models ignore stator flux. Network is modeled using constant admittance matrix calculated at fundamental
frequency. No SS phenomena or harmonic phenomena
Positive Sequence Based DC current components neglected Negative sequence not represented typically (unbalance conditions)
RMS Based Phase based protections poorly represented PLL details, unbalance controls
Specific Limitations Large simulation time step
PLL and inner control loops are critical to performance in weak systems, and these operate with fast time constants
Convergence issues Transient stability iterative nature can be challenging as the system
gets weaker, manifesting in convergence problems. Limited converter electrical representation
Simplified internal controls DC bus (incl. protections, choppers etc) Interfaces with energy source often ignored
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Transient Stability Tool Limitations:
Transient Stability tool limitations: Texas example:
Instantaneous rmsvoltage measurements in PSSE
Fast reactive power response quickly drives voltage high in PSSE
Oscillatory reactive power response in PSCAD as inverters struggle to control Voltage
General recovery dynamics track quite well
Active power recovery is perfectly smooth in PSSE
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So you need EMT. What should an EMT generator model look like? Accurate! Represent full detailed inner control loops of the converters
Eg. current control, PLL, etc. Represent all pertinent control features
Eg. FRT, SSCI damping, voltage control, plant control etc. Represent all pertinent electrical and mechanical configurations
Eg. transformers, filters, gearboxes, etc. Represent all pertinent protections
Eg. OV, UV, DC bus, overcurrent, and many others
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What should an EMT generator model look like? Usable!
Accessible user control for settings which are adjustable Reasonable time‐step (>10 – 20 us) Documentation included, and a test case Self initializing Multiple instance support (and snapshots?) Accepts reference values (no hardcoded setpoints!)
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But Andrew, that’s old material! Yes, and manufacturers have listened!
Current model quality is getting better New IEEE working group (Garth Irwin) on “real
code” model development. All plusses!! State of the art “real code” models are now
becoming widespread. BUT… Manufacturers are now complaining that
their beautiful generator models are being used with overly simplistic system models.
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Doing an EMT study?
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BeautifulDetailed Model
Faul
t
P = 99.43Q = 32.75V = 1.051
VA
VR=0+
Rsource
+
Lsource
Vsys_LGpk
What can you tell from this model? Small Signal control stability
(SCR Tests) (yes, sometimes) SSCI? (no) FRT? (no) Control interactions? (no) Voltage overshoot? (not
necessarily) Insulation coordination? (no) Harmonics? (no) Lightning/TOV/TRV/etc? (no)
Dynamic performance models
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If you want to correctly evaluate these things, you need: Sufficiently big system model (How big? Good question, but maybe bigger than you
think!) Frequency dependent representation of transmission lines Series Capacitors (and sometimes series capacitor arresters and protection) Transformer saturation, tap settings, winding configurations, etc. Detail for nearby power electronics (HVDC, wind, SVC, etc.) Suitable load representation Synchronous machine dynamic representation Shunt capacitors and reactors, neutral reactors, etc. Suitable system equivalent (multi‐port or dynamic if necessary)
Depending on the study, you may also need: Surge Arresters Protection, SPAR/TPAR schemes, RAS, SPS data, other stuff…
Dynamic performance models
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The specific system model you need depends on what problems you’re looking for… Tools are available to simplify model development (full disclosure…
Electranix sells some of these – E‐Tran suite of tools, some of which are licensed as PSS/E modules)
Initialization, data management, library management required… Even with these tools, there is a lot of work to do!
These aren’t your Grandfather’s PSCAD models!
Example System Model:
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BeautifulDetailed Model
Fault
P = 99.43Q = 32.75V = 1.051
VA
VR=0+
Rsource
+
Lsource
Vsys_LGpk
Recent EMT efforts in US: AEP routine SSCI due diligence studies
SSCI instability resulting in series capacitor bypass
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Recent EMT efforts in US: Panhandle study (Round 2),
and South Texas study currently underway… Large scale dynamic performance/system strength studies
Similar studies underway in PacifiCorp (also becoming wide‐spread in Australia!)
Hybrid/Parallel tools make these studies possible…
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Recent EMT efforts in US: Rooftop PV impact studies planned in HECO system
New generic rooftop PV models have been written to reflect both legacy and P1547 compliant inverters
Planned integration into E‐Tran tool to model wide‐area impact of weakening sources and dynamic interaction
DG and utility grade PV penetration reaching un‐explored territory…
Microgrid/BESS studies (Grid‐forming/following inverter systems)
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