March 27, 2015

Power Systems

Jaime De La Ree ECE Department

Early History

•  The “first generator” was developed by Michael Faraday in 1831

•  John Woolrich patents magneto-electric generator in 1842 (for electrotyping)

•  California Electric Light Co. supplies power for arc lighting 1879

•  First power stations in London and New York in 1882

•  1884 the Pearl Street station supplied 59,000 after starting with 2300 bulbs

Power System •  Elements

•  Generators - Input •  Loads - Outputs •  Lines – Ties Gens to Loads

•  Operating Characteristics & Constraints •  Power Balance – KVL & KCL •  Line flows based on Impedances •  No large-scale storage •  Manufacture as “we need it”

Operation •  Key ingredients: Economics and

Reliability

•  Economics – Large Optimization •  Generator Scheduling and Commitments •  Cost minimization

•  Reliability – No violations of voltage levels, Frequency excursions, power flows,……

•  Continuous monitoring •  Control

Blackouts •  1965 North East of the USA •  1977 New York City blackout •  1989 Geomagnetic storm affected Hydo-Quebec •  1996 High summer heat Western North America

and parts of Mexico •  2003 Northeast Blackout •  2003 Malaysia •  2003 Hurricane Isabel •  2003 Sweden and Denmark •  2003 Italy •  ………

Blackouts •  System studies •  Many recommendations •  EMS Centers – SCADA •  Supervisory Control and Data

Acquisition •  Power Flows and Power Injections (Real

and Reactive)

•  State Estimators •  Z = f(x) Z – Mediciones x - State

7

Static State Estimator

•  System is static while “scan” is made •  Technology Limitation

•  Non-Linear •  Iterative

•  Bad Data rejection- important

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Static State Estimator

•  State of the system – EMS

•  Contingency Analysis

•  Operator makes topological and/or operational changes to move the system to a more secure operating point

•  Generation Dispatch

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Static State Estimator

•  Field Sensors – IEDs, PMUs •  SCADA •  EMS •  State Estimation •  Applications

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Static State Estimator •  Data Collection

•  SCADA (Supervisory Control and Data Acquisition)

•  State of the system – EMS

•  Large and Complex Harware-Software Systems

•  Operator makes topological and/or operational changes to move the system to a more secure operating point

•  Generation Dispatch

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A New Paradigm: PMU

• Synchrophasor •  Synchronized Phasor Measurement

• PMU •  Phasor Measurement Unit

2 45°

GPS

Phasors

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Sampled data Phasors Relay

Logic

Digital filtering

Analog filters In

puts

•  Current and voltage magnitudes for relaying require computation of phasors

•  Want to respond to symmetrical rms quantities in the presence of harmonics and other noise •  Impedance relaying requires complex phasors from which impedance can be calculated

Phasors - Definition

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θ

t=0

θ

Real

Imag

inar

y

•  The starting time defines the phase angle of the phasor.

•  This is arbitrary.

•  However, differences between phase angles are independent of the starting time.

Sampling, Fourier

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t

Input signal

xn xn-1 . . x1

Dat

a sa

mpl

es

cosi

nes

sine

s

sin and cos functions

Phasor X = ---Σ xk(coskθ - j sinkθ)

√2 N

Non-Recursive Calc.

16

t

θ1

θ1

θ2

θ2 = θ1 + kφ

The non-recursive phasor rotates in the forward direction, one sample angle per sample.

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t

θ1

θ1

The recursive phasor remains fixed if the input waveform is constant.

θ2= θ1

θ2 = θ1

Recursive Calculation

Why are they Important?

•  Captures Voltage/Current magnitude and angle

•  All units are referenced to a common time

•  All information is time tagged •  High Resolution data •  30 – 60 phasors per second

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PMU –A new view

PMU –A new view

WAMS

•  Synchronous Measurements •  GPS •  Time error in Nano-Sec

•  Time Tagged samples •  Data Concentrators

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Aplicaciones

•  Monitoring •  Information to Operators

•  Control •  Process and Equipment optimal

•  Protection •  …….

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What is it?

•  An adaptive protection scheme is: •  Settings •  Alarms •  Triggering/Threshold values •  Security vs Dependability •  Stress vs Capacity

•  Becomes more attuned with he prevailing conditions of power system

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Adaptive Protection

•  I know…….. Most likely we are going to have arguments with field protection engineers.

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Why?

•  Traditional protection schemes/systems are based on pre-determined studies: •  “Fixed” Loads •  “Static” topologies •  “Known” contingencies •  Hidden Failures are……

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How?

•  Advances in Monitoring Systems: •  Synchronous •  Wide Area

•  Microprocessor-Based IEDs •  Store •  Process •  Communicate

•  All in a common time

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Where?

•  Possibly one of the most interesting questions •  Criticality

•  Generators •  Lines •  Loads

Generators

•  Loss of Excitation protection

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LOF Relay

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Lines

30

Lines

31

LODF

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Changes of Topology

•  The problem here is “load”

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34

Changes of Topology

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Changes of Topology

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Changes of Topology

•  Load-Flow Solution •  The re-distribution is incorrect: The

“swing” bus will shoulder all the necessary change.

•  Generation Loss •  Associated Losses

•  Inertial re-dispatch •  Long-Term the solution may be

appropriate. Short-Term the solution neglects the electrical distances

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Loss of Generation

Where are you?

38

Where are you?

39

Loss of Generation

•  Bus Admittance Matrix •  Zero entry at “ij” indicates that

there is no connection between node i and node j

•  Kron Reduction

40

IgIn

!

"

##

$

%

&&=

Ygg YgnYng Ynn

!

"

##

$

%

&&*

VgVn

!

"

##

$

%

&&

Loss of Generation

•  Let In=0

41

Ig0

!

"##

$

%&&=

Ygg YgnYng Ynn

!

"

##

$

%

&&*

VgVn

!

"

##

$

%

&&

Ig = Ygg −YgnYnn−1Yng"# $%Vg

IEEE – 39 Bus System

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Loss of Generation

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Gen 32 Off

44

Gen 32 Off

45

Gen 7 Off

46

Gen 7 Fuera

47

Gen 7 Fuera

48

Vision

Deploymen

t  Challenge  

Oscilla3on  Detec3on   Voltage  

Stability  Monitoring  

Model  Valida3on  

Transmission  Pathway  and  Conges3on  Management  

Automated  Controls  Detec3on  of  Imminent  Disturbance  Cascading  

High  SGIG  ac3vity  (9-­‐12  projects)  

Source:  DOE  

DG  and  Renewables  Integra3on  

1-­‐2  Years   2-­‐5  Years   >5  Years  

Controlled  System  

Separa3on  

Medium  SGIG  ac3vity  (5-­‐8  projects)  Low  SGIG  ac3vity  (1-­‐4  projects)  No  SGIG  ac3vity  

Frequency  Stability  

Monitoring  

State  Es3ma3on  

Islanding  and  Restora3on  

Wide  Area  Monitoring  and  Visualiza3on  

Post-­‐event  Analysis  

Disturbance  Detec3on  and  

Alarming  

SGIG=smart grid investment grant

Next?

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