Damping Inter-area Oscillations through Decoupled Modulation
Ruisheng Diao, Henry Huang (project lead), Shaobu Wang, Renke Huang
Pacific Northwest National Laboratory [email protected]
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?
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