Real Power Modulation of a Wind Turbine Using Wide-Area

PMU Feedback

Felipe Wilches-Bernal (SNL)Jon Berg (SNL)

David Schoenwald (SNL)Adam Summers (SNL)Brian Pierre (SNL)

Ian Gravagne (Baylor U.) & Ross Guttromson (SNL)with additional contributors:

Big Picture • Overall objective: Build a prototype, demonstration system that can

utilize spinning inertia (energy storage) of a wind turbine to “give and take” real power to grid

• In appropriate frequency band (approx 0.1 to 2 Hz)• Using PMU feedback in real time• Proportional to (but opposing) grid frequency deviations• DOE SBV between Sandia and NIRE (Lubbock, TX)

Big Picture Satellite Clock

PMU (SEL 487)

PMU(SEL 421)Satellite Clock

WSU network

WSU network

InternetInternet

UDPC37.118

SandiaDMZ

SNL XNetSNL XNet

CONET LabCONET Lab

θ2H(z)f2

UDPPacketBuild

ΣΣ

H(z)

fnom

θ1f1+

-

UDPPacket

Encryption

SNL XNetSNL XNet

Supervisory Control

InternetInternet

TTU networkTTU network

UDPPacket

Decryption

Wind ControlRoom

ΣΣ…

Modulated Torque

Command

Damping or RegulationSelector Switch

UDPC37.118

Ts

Ts

Ts

Ts

Ts

Δτ

Vestas V27 Wind Turbine

Visualizationand

Storage

Satellite Clock

Legendf1, f2: Grid frequencyCONET: Control and Optimization od Networked Energy TechnologiesSNL: Sandia National LaboratoriesSWiFT: Sandia Wind Test FacilityTs: GPS Time Stamp LocationTTU: Texas Tech Universityθ1 ,θ2 PMU Voltage Phase AngleWSU: Washington State UniversityXnet: Sandia Research Communication Network

τ

τ+Δτ

Turbine Controller

kΔf=Δτ…

SWiFT Site, Lubbock, TX Sandia CONET Lab, Albuquerque, NM

WSU, Pullman, WA

Network Switch

Turbine Controller

Modulation Controller

Background• Building on work of the Sandia/BPA PDCI modulation project

• B. Pierre et al., "Supervisory system for a wide area damping controller using PDCI modulation and real-time PMU feedback," 2016 IEEE Power and Energy Society General Meeting (PESGM), 2016.

• B. J. Pierre et al., "Open-loop testing results for the pacific DC intertie wide area damping controller," 2017 IEEE Manchester PowerTech, 2017.

• R. Guttromson, I. Gravagne, J. White, J. Berg, F. Wilches-Bernal, and C. Hansen, "SAND2018-772151: Use of Wind Turbine Kinetic Energy to Supply Transmission Level Services," Sandia National Laborotories, Albuquerque, NM, March, 2018.

• T. Knuppel, J. Nielen, K. Jensen, A. Dixon, J. Ostergard, “Power Oscillation Damping Controller for Wind Power Plant Utilizing Wind Turbine Inertia as Energy Storage,” 2011 IEEE Power and Energy Society General Meeting, 2011.

Experimental Setup: PMUs• PMUs

1. SEL 421 located at Washington State U (Pullman, WA), with GPS clock.2. SEL 487 Located at Sandia Labs, with GPS clock.

• Both PMUs transmitting C37.118-2015, “UDP_S”, 60 msg/s (WSU using public internet)

• Both on western grid

Experimental Setup: Modulation Controller• Modulation controller is the design prototype

for PDCI (resides at Sandia “CONET” lab)• LabView-based RT OS• Two operational modes

θ2H(z)f2

UDPPacketBuild

ΣΣ

H(z)

fnom

θ1f1+

-

UDPPacket

Encryption

Supervisory Control

Ts

Ts

𝑚𝑚𝑚𝑚𝑚𝑚 = 𝑘𝑘∆𝑓𝑓

Experimental Setup: SWiFT site• Scalable Wind Farm Technology site: 3 Sandia-owned Vestas V29

turbines in Lubbock. • 225 kW rated power• 29 m blade diameter• Retrofitted for Type IV operation (AC-DC-AC)• Sandia proprietary control system (NI VeriStand platform, with subsystems

compiled from MATLAB/Simulink)• Not on western grid but that’s OK

SWiFTControl House

Experimental Setup: Turbine Controller• Modified the turbine speed controller to accept “torque modulation”

input

Experimental Setup: Torque Modulator

Remove out-of-order packets

Incoming mod signal + origination time stamp

Safety checks

Error recovery

Bandpass

220 225 230 235 240 245 250 255 260

seconds

-25

-20

-15

-10

-5

0

5

10

15

20N

m, k

W

SWiFT Vestas turbine real power modulation: chirp test 3

700

720

740

760

780

800

820

840

860

880

RP

M

Torque Demand (Nm)

Real Power Output (kW)

Gen RPM

Chirp generatedat SWiFT

Chirp Test 1

550 555 560 565 570 575

Seconds

-20

-10

0

10

20

SWiFT Vestas turbine real power modulation: chirp test 4

12

14

16Torque Modulation (Nm)

Real Power Output (kW)

quantization ~.3 kW, 0.1 s

Chirp Test 2

400 450 500 550 600 650 700 750 800 850

Seconds

-20

-10

0

10

20SWiFT Vestas turbine real power modulation demonstration

0

5

10

15

20

Torque modulation (Nm)

Real Power Output (kW)

525 530 535 540 545 550

-20

-10

0

10

20Detail magnification

0

5

10

15

20

Wide area differential mode

0 0.5 1 1.5 2 2.5 3

Frequency (Hz)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Rel

ativ

e si

gnal

am

plitu

de

Stability control signal frequency content

Design bandwith

Tower resonance area

Wide area frequency content

220 230 240 250 260 270 280 290

Seconds

-2

0

2

4

6

8

10

12

14

16

SWiFT Vestas turbine real power modulation: regulation

5

10

Regulation Control Signal

Torque Modulation (Nm)

Real Power Output (KW)Frequency regulation modeSafety sat limit

Return-to-zero

Filters not allowing“slow” trends through

30 35 40 45 50

seconds

-15

-10

-5

0

5

10

SWiFT Vestas turbine real power modulation: signal latency

Control input signal

Torque Modulation (Nm) 39.5 40 40.5 41 41.5 42

-10

-5

0

5

10

Magnification Detail

40 - 65ms

Signal Latency

ℎ ℎ

1 2 3 5 4 6 7 9 8 10

𝜏𝜏𝐵𝐵

𝜏𝜏𝐴𝐴

𝜏𝜏𝐷𝐷𝜏𝜏𝑃𝑃

𝜇𝜇𝑃𝑃

𝜇𝜇𝑄𝑄

PMU sig transmission

PMU1 arrival

PMU2 arrival

Time alignment

Control sig transmission

Control sig arrival

Time alignment

0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

PMU transmission latency (s)

0

500

1000

1500

2000

2500

3000

3500

4000

4500PMU --> ABQ tranmission latency

PMU1 (Albuquerque)

mean = 27 ms

std = 1.3 ms

N = 16700

1 outlier at 93 ms

PMU1 (Washington State)

mean = 70 ms

std = 1.3 ms

N = 16700

PMU transmission delay

0.037 0.0375 0.038 0.0385 0.039 0.0395 0.04 0.0405

seconds

0

10

20

30

40

50

60

70

80

90

100ABQ --> SWiFT network transmission latency histogram

mean = 38.4 ms

std = 0.56 ms

N = 4987 Control signal transmission delay

Q: How’d you get transmissions in/out of Sandia so quickly? A: X-net

A word on comm security• Message Authentication Coding (MAC) using SHA-256 w/ pre-share

key

Illustration of Message Authentication Code Process (www.sqa.org.uk)

ABQ SWiFT

Conclusions, future work• It is possible to modulate the real power output of a wind turbine with zero

“spill” using real-time PMU feedback. • Wind operators can provide grid services (“Wind helps grid!”)• Within appropriate frequency band

• Challenges remain:• Need better measurement of power output (PMU at tower)• Analysis of overall phase margin complicated (filters, delays, sampling,

quantization...)• Freq regulation mode needs more thinking• Explore larger (much larger?) modulation limits• Can it be scaled up? • Ongoing question of cybersecurity for PMU comm

Acknowledgements• Funding from DOE• Technical support from Group NIRE• Sandia and Baylor, support of sabbatical• Additional Sandia personnel

• Will Atkins, Dave Minster, Jon White, Ray Byrne, Matt Reno, members of the Distributed Energy Technology Laboratory (DETL)