RT-HIL Testing of an Excitation Control System for Oscillation Damping using External Stabilizing Signals

M. Shoaib AlmasE-mail: msalmas@kth.se

Associate Professor, DocentElectric Power Systems

DepartmentKTH Royal Institute of

TechnologyStockholm, Sweden

Special Advisor in Strategy and Public

AffairsR&D Department (FoU)

Statnett SFOslo, Norway

PhD CandidateElectric Power Systems

DepartmentKTH Royal Institute of

TechnologyStockholm, Sweden

Dr. Luigi VanfrettiE-mail: luigiv@kth.se

Paper No: 15PESGM1279

BackgroundOne of the supplementary features of commercial Excitation Control Systems (ECS) is to enable power oscillation damping through their built-in PSS• Restricts the end-user to rely on the built-in PSS algorithms and limited

input signals for PSS.– What did you do?

1. External damping signals are provided from different PSS and POD algorithms to the AVR of the ECS (ABB Unitrol 1020)

2. Real-Time Hardware-in-the-Loop Simulation approach is used to explore the possibility of power oscillation damping using external damping signals

– Expectation?1. External damping signals based on local or wide-area measurements contain more

observability of the oscillatory mode.2. Therefore, external signals can provide better damping as compared to the built-in PSS

models in PSS which rely on local measurements (mostly frequency and active power)

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RT-HIL Setup3

Real-TimeSimulator

EthernetSwitch

0-10 V input to amplifier gives output of 0-100V0-10 V input to current amplifiers give current output of 0-6 A

V and IAmplifiers

1 Test Case model being executed in real-time

2

UAC : Generator Terminal Voltage

IB: Generator Stator Current

3

Amplified Generator Voltage (ML1, ML3)

Amplified Generator current (MC2+, MC2-)

Rotor Field Current sent to analog input of Unitrol as Ie External (AI1, BI1)

PWM scaled (0-10V) representing actual field voltage 0.5-99%

Computer with CMT 1000

Low level voltages and currents from the RTS are sent to the amplifiers

Output of PSS models being executed in Opal -RT are fed as analog inputs to the ABB Unitrol 1020 ECS

Unitrol1020

Results• What did you discover/find out?

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ABB Unitrol 1020 ECS is provided withe external damping signals from 4 different stabilizer models to provide oscillation damping

• Multi-Band PSS (IEEE type PSS4B PSS)• Conventional Delta-ω PSS• Acceleration Power PSS (IEEE type PSS 2A/2B)• Phasor-based Power Oscillation Damping (POD) algorithm

80 90 100 1101.5

1.6

1.7

1.8

1.9

2

Rotor Field Current Input to Unitrol 1020 ECS

Time (sec)

Fie

ld C

urr

ent

(pu

)

80 90 100 1100

1

2

3

4

Field Voltage Output from Unitrol 1020 ECS to Generator

Time (sec)

Fie

ld V

olt

age

(pu

)

80 90 100 110-0.04

-0.03

-0.02

-0.01

0

0.01

0.02External Damping Signal Input to Unitrol 1020 ECS

Time (sec)

Dam

pin

g S

ign

al (

pu

)

80 90 100 110

400

450

500

550Power Transfer from Area 1 to Area 2

Time (sec)

Po

wer

(M

W)

No External PSS SignalMB-PSS External Signaldw-PSS External SignaldPa-PSS External SignalPOD External Signal

Conclusions/Recommendations

• Conclusion– The RT-HIL results have shown that the external damping signals from different stabilizer

models can be fed to the commercial ECS to provide adequate damping– Thus liberating the users from the restriction of relying only on the built-in PSS

implementation of the ECS.

• Further Research• Using different types of real PMU signals from an RT-HIL setup as input to an external

hardware-based stabilizer implementation • Experimental proof of the theoretical results in previous publication.

• Noticeable Deviations from Expected Results • Phasor based Power Oscillation Damping algorithm resulted in a slower response in

damping 0.64 Hz inter-area oscillation.• Lower operational limits of hardware ECS to avoid any mis-operation

• Issues due to scalings which cannot be avoided and results in the small variation in the field voltage output by Unitrol 1020 even in steady-state

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