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Helping to keep the lights on,

businesses running

and communities strong®

Mackinac VSC HVDC the First Four Years – Performance and StatusMichael B. Marz, Principal Transmission Planning Engineer

IEEE HVDC-FACTS SubcommitteePES General Meeting Portland, OR, August 8, 2018

Outline

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• Background – Previous Papers/Presentations

• Normal Operation – Modes, Interharmonics,

Faults, etc.

• Unusual Events – Islanding, Last Line Out

• Future – Potential Control & Model Upgrades

Mackinac Back-to-Back VSC HVDC

• CIGRE • 2013 GOTF - Planning

• 2014 Canada - Auto Runback

• 2015 GOTF - PQ/AMR

• MIPSYCON• 2012 Project Design

• 2014 Construction & Testing

• IEEE PES• 2013 HVDC/FACTS Update

• 2017 Panel on HVDC Controls

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• 138 kV AC, 71 kV DC, +/- 200 MW, +/- 100 Mvars, Cascaded Two Level

• Availability During 3-year Warranty Period: Contract 98%, Actual 99.85%

Normal Operations – Modes & Settings

•2017 Operations Summary•Power Transfer 86%, STATCOM 2%, Off 12% of the Time

•Power Transfer Range 20 MW South to 90 MW North

•5-20 MW South 72% of the Time in Power Transfer Mode

•2018 Operations Summary (through July 22)•Power Transfer 84%, STATCOM 15%, Off 1% of the Time

•Power Transfer Range 20 MW South to 40 MW North

•5-20 MW South 33% of the Time in Power Transfer Mode

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Interharmonics and AMR Issues

• Interharmonics Reduce Communication Success with Some AMR Units Using Power Lines to Communicate• TIHVD < 0.4% Seems OK• Exceed ~1% in Power Transfer Mode• Almost always in STATCOM Mode

•When Higher Interharmonics?• Increased Var Output• Certain Times of Day (Mid-Morning)• Weak System, Certain Capacitors Out• Failed IGBT

• Infrequent, ~1 per year• South Failure IHD Up 20%, North Up > 100%• Increases Harmonics (Zero Sequence Issue)

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Response to System Faults

•Typical “Non-Islanding” Fault Response• During Fault North Terminal Goes Into Current Control Mode

• After Fault, Provides MW and Mvars to Help Stabilize System

• Within Seconds of Fault Clearing Returns to Pre-fault MW level

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2 0 1

June 11 Islanding Event Initiation

2 0 1 6

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• 138 kV Double Circuit Tower Fault (157 kA)

• “Successful” Automatic Reclose Attempt

• Why Reclose? Angle, Angle Rate of Change AND Voltage OK?

June 11

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• HVDC Automatically into Island Mode

• Manual Attempts to Connect AC to DC Island Fail (C, L, M)

• Angle Across Open Breaker Too High –Island Sees as Faults

• Successful Reclose with HVDC in Delta Frequency Mode and Minimal Breaker Angle

• No Need to Quickly Tie AC to DC Island

June 14, 2017

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123

45 6 7 8

Voltage AnglesLight Blue - Delta 69 kV

White - Mackinac (S) 138 kV

Purple - Indian Lake 69 kV

Yellow - Hiawatha 138 kV

Green - 9 Mile 69 kV

Dark Blue - Straits 138 kV

Red - Mackinac (N) 138 kV

𝑃 =𝑉1∗𝑉2

𝑋sin(𝛿1 − 𝛿2)

Last Line Out - HVDC Correctly Responds

•If Lose All South 138 kV Lines •South Terminal Shuts Down•North Transitions to STATCOM

•April 1 Both Cable Circuits Lost•Two Cables Cut, Third Damaged•Remaining Cables Reconfigured into One Circuit

•June 8 Trip of Remaining Circuit•North Relays See Fault South of Cable•South Relays Don’t Signal North Relays•Issue with HVDC Short Circuit Model?

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Generator Interconnection Transient Studies

•Check for Control Interactions with Inverter Connected Generation

•Certain Simulations Give Unexpected Results•HVDC Stays in Service for Severe Faults, Trips for Less Severe Faults (With or Without New Gen)

•Issue with Model? Actual Controls? Both? Neither?

•Investigation Ongoing

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Summary

•Mackinac HVDC Reliably Operating as Designed

•Potential Improvements?•Update Controls to Tune Response? (Islanding, etc.)

•Update Short Circuit Model?

•Activate AC Line Emulation?

•Complicated Device in Challenging Location•There is a Long Learning Curve

•Learn as Much About Your Device and System as Early as You Can - Events Will Teach You More

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Questions?

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