Objective:

Technical Approach:

Accomplishments:

Next Steps:

Potential Impact:

1Matthew Weiss, 1Aranya Chakrabortty, 2Farrokh-Habibi Ashrafi, 3Arash Jamehbozorg, and 2Backer N. Abu-Jaradeh

• Dynamical characteristics of the US west coast power grid, often referred to as the WECC systems, are envisioned to transform significantly in the next decade due to the impact of

Large scale integration of renewables like wind and solar (20%-30%) Decrease in centralized generation centers Changing load types

• All of these changes, especially renewable integration, may alter the spectral properties of WECC, especially damping of inter-area modes.

• In this work we propose a wide-area SVC controller design using PMU data feedback to damp WECC’s inter-area oscillation modes, paving the way for further integration of wind and solar resources.

A Wide-Area SVC Controller Design Using a Dynamic Equivalent Model of WECC

References[1] G. Chavan, M. Weiss, A. Chakrabortty, S. Bhattacharya, A. Salazar and F. Ashrafi, “Wide-Area Monitoring and Control of WECC Transfer Paths Using Real-Time Digital Simulations,” Technical Report, NC State University, 2013 (available online: http://people.engr.ncsu.edu/achakra2/scereport.pdf)[2] P. Kokotovic, J. Allemong, J. Winkelman, J. H Chow, “Singular perturbation and iterative separation of time scales,” Automatica, vol. 16 (1), pp. 23-33, 1980.[3] C. W. Taylor and V. Venkatasubramanian, “Wide-Area Stability and Voltage Control,” in Proc. VII Symposium of Specialists in Electric Operational and Expansion Planning SEPOPE, May 2000.[4] G. Franklin, D. Powell, and A. Emami-Naeini, Feedback Control of Dynamic Systems, Pearson, 2010.[5] Y. Chang, Z. Xu, G. Cheng, and J. Xie, “A novel SVC supplementary controller based on wide area signals,” IEEE PES General Meeting, 2006.

1. The wide-area controller and hardware-in-the-loop test-bed will be tested for different types of contingencies at the wide-area communication layer including increased levels of latency, data loss, and PMU data corruption.

2. How can the wide-area controller be protected against these contingencies? How severe can these contingencies become before controller degrades power system operation rather than becomes less effective? The SVC controller will be tested via simulations of these contingency scenarios.

1. The proposed controller is effective at damping inter-area oscillations not just when the WECC model is operating at a particular operating point. The controller significantly damps inter-area modes for many operating points, thereby facilitating renewable injections without much performance loss.

2. The actual location of the SVC as well as the PMUs at the five pilot buses in the reduced-order WECC model exist in the real WECC system. This allows easy implementation of this controller in a real-world setting.

3. As wind penetration grows, coordinated control of the WECC grid may become challenging due to increased levels of model uncertainties. This controller offers a simple, easy-to-implement, and highly robust solution to such system-wide controls at the cost of communication of PMU data from all pilot buses to the SVC bus.

Structured Model Reduction of WECC

A five-area equivalent model of WECC: Model parameters including inter and intra-area impedances,

machine inertias and damping values, and power flows estimated using real PMU data from Southern California Edison

Model created in real-time simulation software platform RSCAD on RTDS racks

Model capable of capturing inter-area modal oscillations during times of transience, but not intra-area oscillations

Simulated event for control design is loss of a generator in Area 5

Closed-Loop Performance for Different Operating Points

Results produced using RSCAD

5 10 15 20 25 30

15.5

16

16.5

17

17.5

18

18.5

19

Time (seconds)

Ang

le (de

gree

s)

Angle Between Area 1 and Area 2

Real Transient ResponseModel Transient Response

5 10 15 20 25 30

9

10

11

12

13

Time (seconds)

Ang

le (de

gree

s)

Angle Between Area 2 and Area 3

Real Transient ResponseModel Transient Response

5 10 15 20 25 30

-16

-14

-12

-10

-8

-6

-4

Time (seconds)

Ang

le (de

gree

s)

Angle Between Area 4 and Area 3

Real Transient ResponseModel Transient Response

5 10 15 20 25 30

-15

-10

-5

0

5

10

Time (seconds)

Ang

le (de

gree

s)

Angle Between Area 5 and Area 4

Real Transient ResponseModel Transient Response

Hardware-in-the-loop Testing and Validation

A Synchrophasor test-bed using RTDS/RSCAD models, PMUs, PDCs, and Real-time Automation Controller (RTAC) housed at FREEDM Center is used for testing:

PMUs and PDC allow collection of phasor data much like an actual substation would contain

RTDS and output GTAO card allow generation of analog phasors for measurement via PMUs

Real-Time Automation Controller (RTAC) allows implementation of real-time controllers acting on phasor data, and allows reintroduction of controller outputs into the RTDS software environment

Model runs in software to recreate power-system dynamics. All other components in the control loop run in hardware.

Wide-Area SVC Controller

A wide-area controller is created using output feedback with PMU data as input and an SVC at Bus 3 as the actuator Controller consists of a low-pass filter,

a lead-lag filter, and a washout filter in series for each inter-area modal component

Attempts to damp each inter-area mode individually

Parameters calculated using model run-time results of modal frequencies, damping, and residues

Controller damps inter-area modes effectively over a wide range of operating conditions

Hardware simulator allows testing of contingencies and introduces hardware signatures to tests, further providing validation of controller functionality in a real-world setting

Simulations allow online testing of SVC capacity and saturation effects

Model effectively shows changes in power system dynamics when wind penetration in the form of DFIGs are introduced at the pilot bus of Area 4 in the reduced-order WECC model

Improvement of Closed-Loop Phase Angle

Response

Damping Impacts after Wind Penetration

0 5 10 15 20 25 30

17

17.5

18

18.5

Time (seconds)

Ang

le (

degr

ees)

Phase Angle 1 Transience

Baseline CasePhase 3 ActivePhase 3 & 4 Active

0 5 10 15 20 25 308

8.2

8.4

8.6

8.8

9

Time (seconds)

Ang

le (

degr

ees)

Phase Angle 2 Transience

Baseline CasePhase 3 ActivePhase 3 & 4 Active

0 5 10 15 20 25 30

−5

−4.5

−4

−3.5

Time (seconds)

Ang

le (

degr

ees)

Phase Angle 3 Transience

Baseline CasePhase 3 ActivePhase 3 & 4 Active

0 5 10 15 20 25 3011.5

12

12.5

13

Time (seconds)

Ang

le (

degr

ees)

Phase Angle 4 Transience

Baseline CasePhase 3 ActivePhase 3 & 4 Active

0 5 10 15 20 25 3016.8

17

17.2

17.4

17.6

17.8

18

Time (seconds)

Ang

le (

degr

ees)

Angle Between Area 1 and Area 2

Baseline ModelWind Online

0 5 10 15 20 25 307.8

8

8.2

8.4

8.6

8.8

9

Time (seconds)

Ang

le (

degr

ees)

Angle Between Area 2 and Area 3

Baseline ModelWind Online

0 5 10 15 20 25 30−9

−8

−7

−6

−5

−4

−3

−2

Time (seconds)

Ang

le (

degr

ees)

Angle Between Area 4 and Area 3

Baseline ModelWind Online

0 5 10 15 20 25 309

10

11

12

13

14

15

Time (seconds)

Ang

le (

degr

ees)

Angle Between Area 5 and Area 4

Baseline ModelWind Online

1North Carolina State University, 1Southern California Edison, 1California State University Los Angeles