m. khederzadeh power & water university of technology (pwut) tehran, iran

Frankfurt (Germany), 6-9 June 2011

M. Khederzadeh

Power & Water University of Technology (PWUT)

Tehran, IRAN.

M.Khederzadeh – IRAN – RIF S3 – Paper 0066

Distributed Energy Resources (DER) Impacts on the Performance of Special

Protection Schemes (SPS)


Presence of DG increases the uncertainty of load and generation balance during extreme contingencies.

In order to compensate for this uncertainty, many SPSs are designed with pessimistic assumptions and consequently overreact.

For example, too much load could be shed in a specific network situation or disturbance.


Motivation of Research


Introduction DER Impact on Performance of SPS SPS and Uncertainties of DERs Simulation Results Remedial Actions Conclusion


Presentation Outline


Power System protection can be divided as: 1. Equipment protection

2. System protection(SPS=System Protection Scheme)

SPS are protections which operate on selected rare contingencies usually outside the design range of the system and equipments.

SPS operates upon the detection of extreme contingencies.


Introduction


Renewable energy resources have an uncertain generation nature.

If real-time data of the DERs are not available to the SPS; its reaction is not optimized.

Impact of the DERs uncertainty on the SPS operation depends on its complexity.

Real time SPSs have a more optimized reaction because they are based on the knowledge of the actual network conditions.


DER Impact on SPS Performance



Sample Network

9 MW Wind Farm(6 x 1.5 MW)

Phasors

pow ergui

Trip

Trip Time

WindTurbine

Protection

Wind (m/s)

Trip

mA

B

C

mA

B

C

Wind (m/s)

Trip

Wind TurbineDoubly-Fed Induction Generator

(Phasor Type)1

Wind Speed(m/s)

A

B

C

Plant2 MVA

?

More info

A B C

Load500 kW

ABCN

a

b

c

GroundingTransformer

X0=4.7 Ohms

[Trip_WT]

pitch

wr

Vdc

wind

[Trip_WT]

A

B

C

A

B

C

Fault

A

B

C

a

b

c

CB2

A

B

C

a

b

c

CB1

A

B

C

a

b

c

B575(575 V)

A

B

C

a

b

c

B25(25 kV)

A

B

C

a

b

c

B120(120 kV)

A

B

C

A

B

C

30 km line 2

3.3ohms

A

B

C

A

B

C

2500 MVAX0/X1=3

A

B

C

a

b

c

25 kV/ 575 V6*2 MVA

A

B

C

A

B

C

20 km line 1

A

B

C

a

b

c

120 kV/25 kV47 MVA

N

A

B

C

120 kV

A

B

C

A

B

C

10 km line 1

<Vdc (V)>

<wr (pu)><Pitch_angle (deg)>



Sample Network Transmission Lines



Sample Network Wind Generation



Wind turbine output power versus turbine speed for different wind speeds

0.6 0.7 0.8 0.9 1 1.1 1.2 1.3

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

5 m/sA

B

C12 m/s

D

16.2 m/s

Turbine speed (pu of generator synchronous speed)

Turb

ine

outp

ut p

ower

(pu

of n

omin

al m

echa

nica

l pow

er)

Turbine Power Characteristics (Pitch angle beta = 0 deg)



Generated P and Q of the wind farm for 8m/s and 14m/s wind speed

0 10 20 30 40 50 60 70 80 90 1000

2

4

6

8

10

12

Time (s)

P (

MW

)

Generated P(MW)

0 10 20 30 40 50 60 70 80 90 100-4

-2

0

2

4

6

8

Time (s)

Q (

Mva

r)

Generated Q(Mvar)



P and Q for wind speed 8m/s. Line1 is disconnected at t=35s. SPS correctly reacts to mitigate Line 2 overloading.

0 5 10 15 20 25 30 35 40 45 50-5

0

5

10

15

Time (s)

P (M

W)

Generated P(MW)

0 5 10 15 20 25 30 35 40 45 50-5

0

5

10

Time (s)

Q (M

var)

Generated Q(Mvar)



P and Q for wind speed 10m/s. Line1 is disconnected at t=35s. SPS overreacts at

t=40s to mitigate Line 2 overloading.

0 5 10 15 20 25 30 35 40 45 50

-2

2

6

10

Time (s)

P (M

W)

Generated P(MW)

0 5 10 15 20 25 30 35 40 45 50-5

-1

3

7

10

Time (s)

Q (M

var)

Generated Q(Mvar)



SPS performance for different wind farm generation in response to a disturbance


Development of a communication infrastructure in order to have enough data of DERs applicable in the SPS decision taking, i.e., transformation of conventional SPS into smart SPS.

Another solution could be implementation of pre-prepared wind/sunshine patterns into the SPS reaction plan.


Remedial Actions


The impact of DERs on the conventionally designed SPS is investigated.

It is shown that the uncertainty embedded in the nature of renewable resources such as wind and sunshine can influence the performance of SPS.


Conclusion


Generally, it is assumed that the DERs are operating at their rated power output, so if real-time data from these sources are not available, then the SPS action to shed generation/load to alleviate overloading of transmission lines is overated.


Conclusion…


In order to improve the knowledge on system security, a statistical approach can be defined to allow engineers to study the behavior of power systems taking into account many uncertainties that influence the results.


Conclusion…


Questions


Thank you for your attention!

m. khederzadeh power & water university of technology (pwut) tehran, iran

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