Damping Inter-area Oscillations through Decoupled Modulation

Ruisheng Diao, Henry Huang (project lead), Shaobu Wang, Renke Huang

Pacific Northwest National Laboratory Ruisheng.Diao@pnnl.gov

June 7-8, 2016 Washington, DC

DOE/OE Transmission Reliability Program

Complex interactions of multiple inter-area oscillation modes

• 0.17 Hz N-S mode • 0.32 Hz Alberta mode • 0.5 Hz E-W mode • 0.55 Hz Montana mode

Credit: Dan Trudnowski

Controller design facing interference between oscillation modes

Modulation Gain

Dam

ping

Rat

io

0.25 Hz

0.31 Hz Modulation

Control

Problem formulation and objective

• Problem – interference of modes: – Design Issue: Signal selection is more complex and constrained by signal

availability – Design Issue: Parameter tuning is more limited due to compromises – Operational Issue: Possibility of adverse impact on damping of one mode while

improving damping of another mode

• Objective – minimize interference in modulation control: – Develop a modulation control that decouple the modes – Enable multiple modulation controllers, one per mode, at the same location

• Opportunities: – Wide-area phasor measurements – Available HVDC and FACTS devices, e.g. PDCI

Technical approach: decouple mode interference by decoupling signals • Supported by linear system

theory • Leveraging filtering techniques • Easier signal selection and

parameter tuning • Less concern about negative

operational impact

M a j o r i n t e r a c t i o n p a t h

" I n d e x " g e n e r a t o r

S U N D A N C E

K E M A N O M I C A

C O L S T R I P

P A L O V E R D E

H O O V E R

G R A N D C O U L E E

M E A D F O U R C O R N E R S

S H A S T A

C A N A D A

M E X I C O

G M S H R U M

Map Credit: John Hauer

Modulation signal: ΔPref

+

Modulation

Signal collection/filtering

Mode 1

Signal decoupling

Phasor Data

Mode 2 Mode 3

Accomplished Deliverables in FY15

# Milestone/Deliverable Target Date

1

Proof-of-concept studies of decoupled modulation control using simulated data with comparison against traditional modulation control.

11/30/2015

2

Development of real-time signal-decoupling methods to separate frequency contents. 2/29/2016

3

Technical report of the design of decoupled modulation control. 5/31/2016

A real-time signal decoupling approach via band-pass filter • Idea: to introduce a band-pass filter to allow certain frequency

components of an input signal to pass through, to a traditional PSS – Goal: to eliminate other frequency components while keeping a

small range

• Filter design

7

Filter PSS

Rotor speed or Active power Vs

Filtered signal

0

2 200

( )s

QF ss s

Q

ω

ω ω

=

+ +

0 0 / 2f ω π= is the center pass frequency

Q is the quality factor

J. Zhang, C. Y. Chung and Y. Han, “N novel modal decomposition control and its application to PSS design for damping interarea oscillation in power system,” IEEE Trans. Power Syst

0 2 4 6 8 10 12 14 16 18 201.93

1.935

1.94

1.945

1.95

1.955

t/s

Rea

l pow

er in

tie-

line

0 1 2 3 4 5 6 7 8 9 100

1

x 10-4

Frequency

Ampl

itude

0.72Hz

Performance test

• 2-area 4-machine system • Two major oscillation modes

– 0.72 Hz – 1.15 Hz

Applying a filter to eliminate the 0.72 Hz mode 0 2 4 6 8 10 12 14 16 18 20

1.93

1.935

1.94

1.945

1.95

1.955

0 1 2 3 4 5 6 7 8 9 100

0.5

1

1.5

2

2.5

3

3.5

4x 10

-3

Frequency

Ampli

tude

1.15Hz

0.72 Hz

Tie-line flow Frequency spectrum

Tie-line flow Frequency spectrum

An eigen-analysis based approach

• Goal: to extract pure mode(s) from state trajectories

• Currently, we are using power system state variables to extract the

desired modes

• In future work, we will use available PMU measurements to extract the target modes for decoupled modulation control

1( ) ( )t t−= ∆z u xHere ( )t∆x is the system state variables which can be obtained from state estimation; ( )tz is the decoupled modes signals which are the feedback signals in the decoupled modulation control.

Preliminary testing on the 2-area system • Decoupled modulation

PSS Vs Pure signal Z(t)

Real parts of eigenvalues

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

Imag

inar

y pa

rts o

f eig

enva

lues

5

10

15

Locations of eigenvalues before control

Locations of eigenvalues after decoupled control

Movement of the target eigenvalue

Next steps

• Design of decoupled modulation control for PSS, HVDC, and load, based on decoupled signal contents

• Evaluation of decoupled modulation control with small- to medium-size test systems on commercial simulation platforms

• Engage appropriate industry groups (e.g. JSIS) and stakeholders (e.g., BPA)

• Planned activities and schedule Task Description Duration

1 Design damping control strategies based on decoupled modulation

12 months

2 Extend decoupled modulation based damping control to HVDC networks

12 months

3 Develop damping-control strategies based on load modulation

12 months

4 Proof-of-concept testing of different damping-control strategies

12 months

Thanks! Questions?