mGrid Operation and Control - Power Systems Engineering ...

HICSS-34

Tutorial 14

January 3, 2001

mGrid Operation and Control PSERC Robert H. Lasseter University of Wisconsin Giri Venkataramanan University of Wisconsin A. P. Sakis Meliopoulos Georgia Institute of Technology © 2001 University of Wisconsin Board of Regents

University of Wisconsin and Georgia Institute of Technology

1

HICSS-34

Tutorial 14

Micro-Grid Operation and Control Robert H. Lasseter

University of Wisconsin A.P.Sakis Meliopoulos Georgia Institute of Technology Giri Venkataramanan University of Wisconsin R.H.Lasseter

University-of-Wisconsin

PSERC

Outline 1. Overview of Micro-sources (1/2 hr) 2. Problems and Issues related to Distribution Systems (1 hr) 3. Power Electronics (1hr) 4. Operation and Control of Micro-Grids Needs and Challenges (1/2Hr)

R.H.Lasseter


PSERC

Power Generation Applications 100s MWs Central Plant

Power Generation

kWs

Distributed Generation 1 MW T/D grid On site generation •Peaking units: •Cost deferrals: •Voltage support:

•Back-up power •Local power & heat •Isolated site •Local voltage support •Cost reduction •Load management

Micro Grid R.H.Lasseter


PSERC

Micro-Turbine Basics Hot Air Recuperator Turbine

Generator

Air

Power electronics

Compressor 3 Phase ~ 480V AC R.H.Lasseter


PSERC

70kW Micro turbine •Installed at $1000/kW (target is $350/kW) •Efficiency 30%

•Air foil bearings •expect in excess of 40,000 hours of reliable operation. •Operation speed 90,000-100,000 RPMs R.H.Lasseter


PSERC

Fuel cell System

R.H.Lasseter


PSERC

Automotive Influence on Fuel Cell Development Experimental F.C. car (Toyota)

1997

Prototype F.C. cars (G.M., DC., Toyota)

Production of F.C. vehicles

2005

2000 Daimler-Chrysler $324 million investment

Fuel cell buses commonplace

Car Fuel Cells must be under $100/kW R.H.Lasseter


PSERC

Ballard PEM Fuel Cell

R.H.Lasseter


PSERC

7 kW Plug Power System PEM Fuel Cell/water heater

QuickTime™ and a Photo - JPEG decompressor are needed to see this picture.

R.H.Lasseter


PSERC

Distributed Generation Business Characterization U. S. Electricity Market $250 Billion Per Year Distributed Generation Expected to Capture 1020% of Market in 10 years Players - Illustrative List Allied-Signal • Micro-Turbines Siemens • Fuel Cells Solar Turbine/Caterpillar Tractor • Engines/turbines Capstone Turbine • Micro-Turbines GE • Fuel Cells/Turbines Others - Ballard, Allison, Williams, Plug Power, PowerCell R.H.Lasseter University-of-Wisconsin Commercial Units/Packaged Solutions Coming to Market PSERC

Generation Efficiencies 1 MW 70% With CHP

60% 50%

CHP

Hybrid Fuel cell

CCTG

Fuel Cell Micro Turbine

40%

Gas Turbine Reciprocating Engines

30% 20% 10kW

100kW

R.H.Lasseter

1 MW

Old steam 10MW


100MW

1000MW

PSERC

On Site Generation Efficiencies 30/80%

Microturbine

30-200 kW

PA Fuel Cells

200-2000 kW 40/78%

PEM Fuel Cells

5-250 kW

Hybrid FC/MT

200-2500 kW 66 kV 24-66 kV 4-16 kV 120-480 V


PSERC

Micro-source Issues • • • • • • •

Low power < 100 kw Low voltage 120-480 volts Inertia-less Power electronic interface Interconnection cost Control (large numbers) Market interactions

R.H.Lasseter


PSERC

Micro Source Dynamics DC Bus

Generator

AC AC DC

• Type of Inverter • Response of “Prime Mover”

R.H.Lasseter


PSERC

Inverter P-Q response

Line Commutated pu

CSI - Line Commutated VSI - PWM with Voltage Linecontrol

P & Q

R.H.Lasseter

University-of-Wisconsin Time seconds

PSERC

20 sec

R.H.Lasseter


PSERC

Micro-Source Dynamics DC Bus

AC AC

Power Source DC Power 1.0

Fuel Cells 20-100 seconds

Micro-turbine

0.5 0.0 R.H.Lasseter

10 time sec.

20


PSERC

Load Tracking Problem Power electronics – Inertia-less system – Fast response

Instantaneous power balance – Connect to grid – Use storage on dc bus – Storage on the ac bus – Include rotating machines in Micro-grid

R.H.Lasseter


PSERC

Quality of Power Perspectives UTILITIES

CUSTOMER’S

There are less than four

Electricity problems disrupting equipment and production are originated by voltage sags, with duration less than 1/2 second

interruptions per year with a cumulative interrupted average of less than 2-hours/year

95 percent of interruptions are due to faults or outages on the T/D system 80 percent of the interruptions are due to distribution system components R.H.Lasseter

There are about 10-15 times per year that voltage sags occur with the voltage dropping below 70%

Production equipment contains electronics sensitive to power quality problems University-of-Wisconsin

PSERC

Micro-grid concept assumes: • Large clusters of micro-sources and storage systems • Close to loads with possible CHP applications • Provide Quality of Power required by Customer • Presented to the grid as a single controllable unit (load & source)

R.H.Lasseter


PSERC

Load Control using a Connected Micro Grid Load control

Pload

Control P set point R.H.Lasseter


PSERC

Next 1. Problems and Issues related to Distribution Systems Power 2. Power Electronics Sources

R.H.Lasseter


PSERC

mGrid Operation and Control Problems and Issues Related to Distribution Systems

A. P. Sakis Meliopoulos Georgia Institute of Technology

Tutorial 14 HICSS-34 Jan 3, 2001

Georgia Tech

PSERC 1

The mGRID Concept – Distribution System Backbone Photovoltaics Interface Protection

RTU

Micro-Grid Management System

Converter

CATV& Communications RTU

RTU Control

Data Aqcuisition

Sensitive Load RTU Static Conditioner

Fuel Cell

Variable Speed Drives Converter

Interface Protection Interface Protection Converter

Georgia Tech

Microturbine / Generator

PSERC 2

Distribution System Backbone Issues Safety Voltage Profile Power Quality Reliability Protection Unbalance/Asymmetry Stray Voltages and Currents Electromagnetic Compatibility Issues Non-autonomous/Autonomous Operation PSERC Georgia Tech

3

Safety

Let-Go Current (Milliamperes) - RMS

100

80

60

40

sheep

300

Kiselev Dogs Dogs Ferris Dogs

Fibrillating Current (mA RMS)

Let-Go Current

200

100

50%

20

0.5%

Let-Go Threshold

Minimum Fibrillating Current (0.5%)

Maximum Non-Fibrillating Current (0.5%)

99.5% Dangerous Current

pigs

calves

Ventricular Fibrillation

0 0

20

40 60 80 Body Weight (kg)

100

Safe Current 0 5

10

50

100

500

1000

Frequency (Hz)

Georgia Tech

5000

PSERC 4

The Electrocution Parameters

B

A1

A2

rbody B

A1

A2

Veq req

Georgia Tech

PSERC 5

Applicable Standards (IEEE & IEC): Non-Fibrillating Body Current as a Function of Shock Duration

PSERC Georgia Tech

6

Earth Current / GPR / Worst Case Condition

P ro g ra m X F M - P a g e 1 o f 1 c : \ w m a s te r \ ig s \ d a t a u \ g p r _ e x 0 1 - M a y 1 4 , 2 0 0 0 , 0 1 : 5 1 :4 4 . 0 0 0 0 0 0 - 2 0 0 0 0 0 . 0 s a m p le s / s e c - 2 4 0 0 0 S a m p le s 2 .5 0 1

P h a s e _ A _ L in e _ C u r r e n t_ _ B U S 1 0 (k A )

1 .6 9 4 8 8 7 .3 m 8 0 .7 6 m -7 2 5 .8 m -1 .5 3 2 -2 .3 3 9 -3 .1 4 6 -3 .9 5 2 1 .0 5 2

E a r t h _ C u r r e n t _ _ G r o u n d _ a t _ B U S 2 0 (k A )

7 1 7 .1 m

Important Issues

3 8 2 .5 m 4 7 .8 1 m -2 8 6 .8 m -6 2 1 .5 m -9 5 6 .1 m -1 .2 9 1 -1 .6 2 5 4 4 .0 2 0

4 4 .0 4 0

4 4.06 0

4 4 .0 8 0

4 4 .1 0 0

Grounding and Bonding Single Ground/Multi Ground Load/DER Configuration Transmission Interconnection

PSERC

Georgia Tech

7

Power Quality Disturbances Lightning Switching Power Faults Feeder Energization inrush currents, Motor Start Loading imbalance Harmonics, Resonance EMI

Impact on End User Voltage Distortion, Sags, Swells, Outages and Imbalances

Design Options Configuration Grounding Overvoltage Protection (arresters), Fault Protection Use of Steel/Aluminum conduit, Etc.

Georgia Tech

PSERC 8

Lightning Caused Voltage Sags, Swells and Outages

S wf

S A

B

C

N

S dt

D

PSERC Georgia Tech

9

Lightning Caused Voltage Sags, Swells and Outages Effects of Grounding and Protection

PSERC Georgia Tech

10

Voltage Sags & Swells and Grounding R0/X1 6

Coefficient of Grounding

95/164

5

100/173

4

C

90/155

3

g

actual VLG = no min al VLG

85/147

2 80/138

1

75/129 70/121

X0/X1 0 57/100

1

2 65/117

Georgia Tech

3

4

5

6

PSERC 11

Voltage Sags & Swells During a Ground Fault A A V

A

V

A

V

A

A

A

L

B U S 10

B U S 20

R

B U S 30

B U S 40

G

Close

Transmission Line Voltage & Current Profile Distribution Line, 12 kV Displayed Quantity

Voltage Reference

Volt age

Remote Earth

Current

Neutral

Nominal Voltage 6.92

Plot Mode Absolute

kV (L-L)

Deviation

Voltage (kV)

Ground 2.00

Distance 1.250

0.00

_A -5.810

-2.00

_B 0.3334

-4.00

_A -6.00 _B _C _N -8.00 0.00 BUS40

_C 0.9744

V

A

V

A

V

A

Comments The Data of the Figure can be used to generate nomograms and statistical distributions of voltage sags and swells for a specific location (IEEE P1346) A better approach is outlined next

_N 0.00 0.75

1.50 2.25 Distance (miles)

Program IGS - Form CODE_102A

Georgia Tech

3.00

3.75 BUS50

PSERC 12

Statistical Distribution of Voltage Sags/Swells 4.0 Fuse

Transformer

L1 N L2

3.0 Sensitive Electronic Equipment G

Ground Loop

Ground Rods

Probabilistic Approach to Power Quality Analysis

Voltage (kV)

Arrester

2.0

1.0

PQ Characterization 106

Design Options for PQ Enhancement

Georgia Tech

105

104

103

102

10

PSERC 1

0.1

Frequency (Hz)

13

0.01

Ferroresonance 5

Comments 2 PHASES ENERGIZED

Maximum Overvoltage (pu)

4

Resonance Between the Inductance of a Steel Core and the Circuit Capacitance

3

Vulnerable Systems: Medium Voltage Cable with Transformers/Regulators

1 PHASE ENERGIZED

2

Cases of “Stuck” Pole – Single Phase Protection 1

0

0.1

1

10

100

Capacitive/Inductive Impedance Ratio

Georgia Tech

1000

PSERC 14

Comments

Harmonic Resonance

Harmonic Resonance Has Multiple Modes and Resonance Frequencies BUS100

BUS90

System May Be Vulnerable When Resonance Coincides with a Harmonic Frequency

BUS80 1

BUS110 BUS120

2

BUS30

BUS40 BUS50 BUS60

When Problem is Known, Solution is Very Simple Detuning

BUS70

Positive Sequence Frequency Scan at Bus BUS70/ P

Frequency Scan At 2-Node Port: BUS70_A to BUS70_N

Impedance Magnitude

Impedance Magnitude

334.5

100

334.5

10.0

Magnitude (Ohms)

Magnitude (Ohms)

163.4

10.0

Magnitude (Ohms)

1000

100

Frequency (Hz)

872.1 1.00

0.100

1.00 0.00

400

800

1200

1600

2000

Table

0.00

400

800

1200

Frequency (Hz)

Frequency (Hz)

Impedance Phase

Impedance Phase

Frequency (Hz)

150

80.0

334.5

75.0

40.0

Phase (Degrees)

120

Phase ( Deg)

Frequency (Hz)

0.00

5.501

Phase ( Deg)

Magnitude (Ohms)

1000

1600

2000

Table Frequency (Hz)

0.00

Phase (Degrees)

-75.0

-150

-40.0

-225

-80.0 0.00

400

800

1200 Frequency (Hz)

Pro gram WinIGS - Fo rm FSCAN_RES

Georgia Tech

1600

2000

Close

0.00

400

800

1200 Frequency (Hz)

Pro gram WinIGS - Fo rm FSCAN_RES

1600

2000

Close

PSERC 15

Reliability Reliability Indices for Distribution Systems (Utility Perspective)

Reliability Measures (Customer Perspective)

SAIFI: System Average Interruption Frequency Index (interruptions/year and customer)

Voltage Sags Voltage Swells Momentary Outages Load Interruption EMI

SAIFI =

Total Number of Customer Interruptions per Year Total Number of Customers Served

SAIDI: System Average Interruption Duration Index (hours/year and customer) SAIDI =

Total Number of Customer Interruptions Durations per Year Total Number of Customers Served

CAIDI: Customer Average Interruption Duration Index (hours/interruption) CAIDI =

Total Number of Customer Interruption Durations per Year Total Number of Customer Interruptions

ASAI: Average Service Availability Index Total Customer Hours Service Availability per Year ASAI = Customer Hours Service Demand

Georgia Tech

Comments Good Methods for Utility Applications Exists (Markovian) End User/DER Methods Needs Further Research (NonMarkovian Processes)

PSERC 16

Cost of Reliability Example Power requirements: 3000 VA power Average power consumption is 2000 Watts Power utility reliability: SAIFI = 1.5, SAIDI = 45, Momentary = 30 Sector customer damage function: commercial per Table Below

Calculations MWhrs consumed: 17.52 Cost of two 20 minute outages: (3.0)(17.52)(2) = 105.12 Cost of five 1 minute outages: (1.0)(17.52)(5) = 87.60 Cost of momentary: (1.0)(17.52)(30) = 525.60 Annual cost of interruptions: 718.32

Comments Cost of utility power (assuming $0.10 pwr kWhr): $1,752 per year

Survey of Cost of Interruption Sector Customer Damage Function ($/MWhr) Sector\Duration Residential Commercial Industrial Large User

Mom 0 1.0 6.0 2.0

Georgia Tech

1 Min 0 1.0 6.0 2.0

20 min 0.1 3.0 13.0 2.0

1 hr 0.4 10.0 24.0 3.0

4 hr 3.0 36.0 64.0 3.0

8 hr 6.0 74.0 106.0 4.0

24 hrs 20 94.0 135.0 5.0

PSERC 17

Reliability Research Issues Battery Energy = 15 min Cap Prob Freq Dur R

R

0 300 600 900

R

5e-4 3e-6 3e-3 0.996

13.0 9e-4 0.46 13.5

0.3 30 58 648

Battery Energy = 30 min I

I

I

Cap Prob Freq Dur 0 300 600 900

7.2e-5 13.0 0.3 2.7e-5 5e-3 47 3.8e-3 0.52 65 0.9961 13.5 648

PSERC Georgia Tech

18

Protection Typical DERs Protection

Protection Issues Fault Protection (Current Limited DERs, Remote Contribution, Ground Impedance, etc.) Faulted Circuit Indication Fault Location and Isolation Detection of Hot “Down” Conductors

PSERC Georgia Tech

19

Unbalance/Asymmetry Most Power Circuits Are Asymmetric

1 zmax − zmin S1 = 2 z1

1 ymax − ymin S2 = 2 y1

Asymmetry Factor

0.06

0.04

Series Admittance

0.02

Shunt Admittance

0.0 180

660

1140

1620

2100

Frequency (Hz)

Other Sources Single Phase Loads End Use Equipment Induction Motors

Georgia Tech

PSERC 20

Induction Motor Response to Unbalance/Asymmetry Typical Distribution System Example Close

Device Terminal Multimeter Case:

BUS100

Device:

System Asymmetry and Imbalance Example Induction Motor

BUS90

Total Power

Voltage

L-G

Phase Quantities

Per Phase Power

Current

L-L

Symmetric Comp

BUS80 1

BUS30

BUS110 BUS120

2

BUS40

MCLOAD1_A

BUS50 BUS60 BUS70 1 MCLOAD2 IM

Voltages MCLOAD1_B

2

MCBUS1

MCLOAD1_C RGROUND

ANGSPEED2 MCLOAD1 IM

ANGSPEED1

Combined Effects of System Component Asymmetry and Imbalanced Loads

Va Sa S Sc Ia Sb

Ic

Ref Vc

Currents MCLOAD1_A

Comments

Va Vb Vc

MCLOAD1_B MCLOAD1_C

Ia Ib Ic

Ib

P 367.6 kW, Q 178.3 kVar S = 4 08.5 kVA, PF = 89.97 % Pa 120.2 kW, Qa 69.04 kVar Pb 114 .8 kW, Qb 50.20 kVar Pc 132.5 kW, Qc 59.09 kVar Va = 255.2 V, 55.34 Deg Vb = 24 5.3 V, -63.85 Deg Vc = 24 9.0 V, 175.7 Deg Ia = 54 3.0 A, 25.4 7 Deg Ib = 510.9 A, -87.4 6 Deg Ic = 582.9 A, 151.6 Deg

Vb

Pro gram WinIGS - Fo rm FDR_M ULTIM ETER

Important Factors: Configuration Transformers Load Balancing

Georgia Tech

PSERC 21

Stray Voltages and Currents ~ I sky Sky Wire

Comments

HA LA HB

LB LC

HC Neutral

~ I neutral

Counterpoise

Ground Mat

~ I counterpoise

Ground Rod

Ground Rod

~ I earth

CATV

Single Phase Loads Generate Current Flow in the Parallel Path of Neutral and Soil/Grounds Typical Distribution 50-70% in Neutral, 50-30% in Soil/Grounds Neutral Voltage Typically 2 to 12 Volts

Properly Designed mGRIDs can Practically Eliminate Stray Voltages and Currents

Georgia Tech

PSERC 22

Electromagnetic Compatibility Issues SOURCE BUS10

Magnetic Field Near Nonmagnetic Conduit Enclosed Circuit

BUS100

G

Plot Circle Radius

0.500

Return

Plot Along Straight Line Plot Along Conduit Centered Circle

Feet

Update

BUS200

Magnetic Field

6.00 inches 375

Example of Two Series Circuits in Magnetic and Aluminum Conduits

MilliGauss

300

225

150

BUS400

75.0 1Ph

0.00 0.00

Magnetic Field Near Steel Conduit Enclosed Power Circuit (ID=3) Plot Circle Radius

0.50

Zoom All

Angle

319.1

Field

270

360

365.9

Update

Magnetic Field

6.00 inches

Zoom Out

180 Angle(Degrees)

Program GEM I - Form EM F_CI RCLE

Plot Along Conduit Centered Circle

Feet

Zoom In

Return

Plot Along Straight Line

90.0

Comments

76.0

72.0

EMI can generate serious problems

MilliGauss

68.0

64.0

60.0

56.0 0.00

Zoom In

Zoom Out

Zoom All

Angle

Program GEM I - Form EM F_CI RCLE

Georgia Tech

90.0

244.1

180 Angle(Degrees)

Field

270

360

75.81

The mGRID concept offers an opportunity to rethink design issues and optimize EMI performance

PSERC 23

WEMPEC

Inverters in Microgrids

Giri Venkataramanan Department of Electrical and Computer Engineering University of Wisconsin-Madison 3 Jan 2001

[email protected] 3 Jan 2001

Microgrids Short Course

GV 1

WEMPEC

Outline • Description of inverter types and characteristics • Inverter control objectives • Inverter dynamic modeling • Summary

3 Jan 2001


GV 2

WEMPEC

Inverter types PWM inverter z Multilevel inverter z Naturally commutated current source inverter z

3 Jan 2001


GV 3

WEMPEC

PWM Synthesis – A, B & C phases Vdc Va

Vb

Vc

• Phase shift between waveforms may be varied • Amplitude of waveforms may be dissimilar • All the three phase voltages could have an average Vdc/2 common mode voltage • Causes a neutral shift • Will cancel out in the line-line voltages 3 Jan 2001


GV 4

WEMPEC

Realization using IGBTs

Vdc

3 Jan 2001

Va

Vb


Vc

GV 5

WEMPEC

Multilevel Inverters

Vdc

+ other phases

Vdc Vdc

+ other phases

Vdc

3 Jan 2001


GV 6

WEMPEC

Typical waveforms Pole voltage Vdc Vdc/2

Line-Line Voltage

Stepped synthesis also possible 3 Jan 2001


GV 7

WEMPEC

Three Phase Current Source Inverter • Two Pole Three Throw Switches

Stiff Current

1P3T

1P3T

3 Jan 2001


GV 8

WEMPEC

CSI Converter Realization (Thyristors) z

1P3T

Stiff current

z

Natural commutation Leading power factor load

Three phase a voltages

1P3T

3 Jan 2001


GV 9

WEMPEC

3 wire direct output • DC voltage level has to be bigger than peak lineline voltage • No path for zero sequence currents from inverter

3 Jan 2001


GV 10

WEMPEC

4 wire interface using star-delta transformer • DC voltage level free variable because of transformer turns ratio • Zero sequence currents on star side circulates within the loop of the delta side

3 Jan 2001


GV 11

WEMPEC

Single line equivalent circuit and phasor diagram Vi

Vi IL

IL Vo

It

Vo It

Vac

Vac

• Vac – PCC voltage • Vo – Point of Load (POL) Voltage 3 Jan 2001


GV 12

WEMPEC

Microgrid Energy and Power Quality Management Functions • Load profile control • Source utilization • Peak-shaving • Reactive power injection • POL voltage control • Voltage imbalance correction

3 Jan 2001


GV 13

WEMPEC

Voltage sag correction Nominal condition Vi

IL Vo

It

Vac

Operation under sag (Same real power transfer level)

Operation under sag (Reduced real power to grid)

3 Jan 2001


GV 14

WEMPEC

Voltage imbalance correction

• Input voltage – Brown • Output voltage – Cyan • Phase currents – Green • Note increase in current stress on phases with large sag 3 Jan 2001


GV 15

WEMPEC

Fault Management

Vi

IL

It

Vo

Vac

Fault

3 Jan 2001


GV 16

WEMPEC

Operation under transients Load transients z System transients z

– –

Capacitor switching Power quality events

Delayed source response z Islanding z Reconnection z

3 Jan 2001


GV 17

WEMPEC

Key Control Issues Power flow control z Frequency control z Local voltage control z Reactive power control z

Power sharing z Frequency matching z

3 Jan 2001


GV 18

WEMPEC

Power throughput of inverter VacVo sin δ P= Xt 2

Vo VacVo cos δ Q= − Xt Xt

3 Jan 2001


• Angle between Vac and Vo determines power flow • Magnitude of Vo determines reactive power flow

GV 19

WEMPEC

Modeling objectives • Need to model dynamic properties • Control input and real power flow or power angle • Control input and reactive power flow or voltage magnitude

3 Jan 2001


GV 20

WEMPEC

Typical controller structure (classical) + Vac 1

+ Voltage command

+

Current Regulator

Voltage Controller -

PWM Converter and LC Filter

-

Vo

Ls

It

IL Vi

Current feedback

Voltage feeback

3 Jan 2001


GV 21

WEMPEC

Typical controller structure Flux vector + Vac 1

+ Flux command

PWM Converter and LC Filter

Flux Regulator

Vo

-

Vi Flux feedback

1 λi

Vi

s

IL

λi

3 Jan 2001

It

Ls


Vo It Vac

GV 22

WEMPEC

Key control variables Magnitude and Phase angle Modulation input z Inverter output z Filter inductor current output z Capacitor voltage output z

3 Jan 2001


GV 23

WEMPEC

Key control variables

m(t ) = m(t ) e

j∠m ( t )

vi (t ) = vi (t ) e

j∠vi ( t )

iL (t ) = iL (t ) e

j∠iL ( t )

vo (t ) = vo (t ) e

j∠vo ( t )

Instantaneous phase quantities are projections of the rotating vectors on appropriate axes 3 Jan 2001


GV 24

WEMPEC

Dynamic Equations d L iL = vdc m cos(∠m − ∠iL ) − vo cos(∠vo − ∠iL ) dt d L iL ∠iL = vdc m sin(∠m − ∠iL ) − vo sin(∠vo − ∠iL ) dt

vo d C vo = iL cos(∠iL − ∠vo ) − dt R vo d C vo ∠vo = iL sin(∠iL − ∠vo ) − dt R

3 Jan 2001


GV 25

WEMPEC

Steady state operating condition 0 = Vdc M cos(∠M − ∠I L ) − Vo cos(∠Vo − ∠I o ) L I L ω = Vdc M sin(∠M − ∠I L ) − Vo sin(∠Vo − ∠I L ) 0 = I L cos(∠I L − ∠Vo ) −

Vo R

C Vo ω = I L sin(∠I L − ∠Vo ) −

3 Jan 2001


Vo R

GV 26

WEMPEC

Steady state operating condition 0 = Vdc M cos(φ miL ) − Vo cos φvoiL L I L ω = Vdc M sin φ miL − Vo sin φvoiL 0 = I L cos φiL vo −

Vo R

C Vo ω = I L sin φiLvo −

Vo R

Classical phasor solution 3 Jan 2001


GV 27

WEMPEC

Small signal model at operating point x&= Ax + Bu y = Ex + Fu   0    −ω  IL A=  Vo   RC I L  ω  I L 

3 Jan 2001

ωI L 0

~ u= m

− Vo LR I L − ωC Vo 2

IL L − ω Vo 1 RC

−1 RC −ω Vo

2 − ωC Vo   2 IL L  2  − Vo  2 LR I L    ω Vo   −1  RC 


 ~ iL   ~ ∠i x =  ~L v  o  ~  ∠vo 

Vdc cos φ miL    L  V sin φ  dc miL  B=  L IL    0     0

GV 28

WEMPEC

Transfer function z

Magnitude of modulation to output voltage 60 MG(f k)

40 20 0 10

1 .10

100

3

1 .10

3

1 .10

4

fk 0

AG( f k) 90

180 10

1 .10

100

4

fk 3 Jan 2001


GV 29

WEMPEC

Perturbations in time domain 200 Voac( t , 1000 ) Voa ( t , 1000 )

0

200

0

1

2

3

4

5

6

7

8

9

10

t ⋅ 1000 50 Ioa( t , 1000 ) Ioac( t , 1000 )

0

50

0

1

2

3

4

5

6

7

8

9

10

t ⋅ 1000

3 Jan 2001


GV 30

WEMPEC

Vectors on the Complex Plane 300 200 100 Im( Vocomplex( t , 1000 ) )

0 100 200 300

300

200

100

0

100

200

300

Re( Vocomplex( t , 1000 ) )

60

Output current complex vector 40 20 Im( Iocomplex( t , 500 ) )

0 20 40 60

60

40

20

0

20

40

60

Re ( Iocomplex( t , 500 ) )

3 Jan 2001


GV 31

WEMPEC

Properties of the dynamic model Eigen frequencies of small signal model

 −313.396 + 629.17i    −313.396 − 629.17i   −313.396 + 509.17i    −313.396 − 509.17i 

3 Jan 2001

Eigen frequencies of LC filter (incl. damping effects)

= 569 Hz

Excitation frequency

= 60 Hz


GV 32

WEMPEC

Dynamic interaction issues z z z z z z z 3 Jan 2001

Angle input to output transfer functions Cross coupling transfer functions Selection of controllers and tuning Outer loop effects (Real and reactive power, droop, etc.) Frequency synchronization Interactions between multiple parallel units EMI filter interactions Microgrids Short Course

GV 33

WEMPEC

z z z z z z z 3 Jan 2001

Summary

Inverter modeling important aspect of microgrid design Stiff dc bus with adequate storage decouples prime mover dynamics Inverter dynamic model based on rotating vectors Model reduces to phasor model at steady state Small signal model properties outlined Various transfer functions can be determined, (esp. angle and frequency) Extend and integrate into system models Microgrids Short Course

GV 34

Operation and Control of Micro-Grids Robert H. Lasseter University of Wisconsin

R.H.Lasseter


PSERC

Micro-grid concept assumes: • Large clusters of micro-sources and storage systems • Close to loads with possible CHP applications • Customer Quality of Power • Presented to the grid as a single controllable unit (load & source)

R.H.Lasseter


PSERC

• Solid state breaker • Generation & storage • Motor Loads

Micro Grid open

13.8 kV

480V

480V 6

5 8

M5 M8

R.H.Lasseter

480V

9 M9


PSERC

Control of P &Q using PWM Inverters

Vinv

E

Inverter

P ∝δ p 0

Q ∝Vinv

Vinv

δ

0 R.H.Lasseter


E PSERC

Basic P Q Controller Va V

b

Vc E

a

E

b

Ec

ψv Flux Vector Calculator

ψv o

δv

Inverter Flux Vector Control

ψE

Flux Vector Calculator

δE

Ea Eb Ec

R.H.Lasseter

e

Po

Ib c

Switch

δP o

Ia I

Inverter r

P&Q Calculation

P _

+

_ Q

+

p-i

δP o

p-i

ψv o

Qo


PSERC

Basic P & Q Response

P

Current

Q

R.H.Lasseter


PSERC

Micro Grid connected to T/D Grid Micro-Sources Provide • Control of local bus voltage • Control of base power flow Fast Load tracking is provided by the grid Micro Grid: Dispatchable load to the grid

R.H.Lasseter


PSERC

Micro Grid

• P control • V control of 8 & 9

13.8 kV

480V

480V 6

5 8

M5 M8

R.H.Lasseter

480V

9 M9


PSERC

P V controller

8 on Bus 8

9 on Bus 9

R.H.Lasseter


PSERC

Isolated Micro Grid Issues • Instantaneous power balance – Use storage on dc bus – Storage on the ac bus – Include rotating machines in Micro-grid

• Load Sharing • Frequency Control R.H.Lasseter


PSERC

Island System P ~ Sin(δ1−δ2)

V2 / δ 2

L2 Increase L 2 R.H.Lasseter

V/ 1 δ1

L1 University-of-Wisconsin

PSERC

P ~ Sin(δ1−δ2) ω0

V1

ω0 > ω1 > ω2

V2 δ2 R.H.Lasseter


PSERC

Frequency Droop ω ωo

P02

P01

ω1

ω min P P2max P1max R.H.Lasseter


PSERC

Power Droop ωi (t) = ω 0 − mi (Pc,i − Pi (t)) ω + +

E

s _

ωo

δ

P

k" s

Pc

+

_

_

_ m

+

1 s

+

_ k'

+

p-i

δP o

-

Po

R.H.Lasseter


PSERC

P V Controller with Droop ψ E0

Eo

1

ω

ω

E

+ _

s

V

Flux Vector Calculation

I ωo Po R.H.Lasseter

ψE ψ

Q E P&Q Calculation

p-i

I

ψ

vo

v

Inverter Flux δv Vector Control

δE

P Power with droop


δ

Po

PSERC

Island Micro Grid

• Solid state breaker • Generation & storage • Motor Loads open

13.8 kV

480V

480V

Non-critical Loads 6

5 8

M5 M8

Critical Loads R.H.Lasseter

480V

9 M9

Critical Loads University-of-Wisconsin

PSERC

Voltage on Buses 8 & 9

R.H.Lasseter


PSERC

Injected P & Q Buses 8 & 9

R.H.Lasseter


PSERC

Frequency Droop ω ωo

P02

P01

ω1

ω min P P2max P1max R.H.Lasseter


PSERC

Frequency Hz

Frequency at bus 8

Time seconds

R.H.Lasseter


PSERC

Sensitive loads (Quality & Service)

Power Quality is the attribute of electric power which enables utility customers’ electrical and electronic equipment to operate as intended

R.H.Lasseter


PSERC

Voltage Sensitivity 5-10 cycles 150

100

CBEMA

Type 1 50 Type 2 CBEMA

0 1 0 -1 100

R.H.Lasseter

101

102

103

DurUniversity-of-Wisconsin at ion ( 6 0 Hz Cy c les)

PSERC

Shunt current injection Restored Voltage

Voltage Sag 1.0

1.0

0

0

-1.0

-1.0

injected current Critical Load R.H.Lasseter


PSERC

Premium Power Micro Source

•Power Power Source •UPS •Voltage control unbalance frequency R.H.Lasseter

AC DC DC


DC

PSERC

Voltage Sag Regulator -* Vs=0 V d

dq

abc -

Negative component V c

V s PID

Ø s

V q

dq-

s V

dq

V + V dq

V s

abc

+* Inverter

s

+ V c

+

d abc

dq-

dq+

PID

-

+ V q dq+

+ Ø s

dq

abc

Positive component R.H.Lasseter


PSERC

Inverter Response to SLG

R.H.Lasseter


PSERC

Micro Grids & Premium Power • Generation Close to loads – Local reliability – Possible CHP applications

• Premium Power – UPS functions – Back-up service – Custom Power functions

R.H.Lasseter


PSERC

Research Needs 1. Clear interfaces/functions to the Grid 2. Micro-Grid protection 3. Plug & play controls 4. Placement tools including CHP.

R.H.Lasseter


PSERC