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PowerApps --- Excitation Systems


Validation and Results

 

Single Machine – Infinite Bus (SMIB) Benchmark

Highlights:

i.         Comparison between PowerApps Transient Stability Simulation results and a SMIB System Benchmark [2]. [Refer Chapter 13, Example 13.2, pp 864-869]

ii.       Comparison of generator absolute rotor angle, exciter output voltage, active power output, and terminal voltage responses.

iii.      Models of AVR used are IEEE type 1 excitation system, IEEE type 2 excitation system, IEEE type 4 excitation system, and IEEE type 5 excitation system. The parameters of each of these excitation models were chosen to match with the simplified excitation system model of the text book example, with the objective of making comparison between PowerApps simulation and the text book results.

 

1.       System Description

A single machine infinite bus system transient stability study is applied in this validation case.  The system is well documented [2]. The system consists of a generator, a bus and an infinite bus connected by transmission lines as shown in Figure 1. The infinite bus is modeled in PowerApps as a generator with large MVA rating connected to a bus.

Figure 1 SMIB Benchmark System SLD

2.       System Data

a.       Bus Data:

Bus No.

Pg (MW)

Qg (Mvar)

Pl (MW)

Ql (MW)

Bus Volt (KV)

Vsp (p.u)

Asp (p.u)

LT

1998

0

0

0

24

1

0

INFBUS

0

0

0

0

230

0.90081

0

Table 1 Bus Data (SMIB)

b.      Line Data:

From --> To

R (p.u)

X (p.u)

B2 (p.u)

HT --> INFBUS

0

0.5

0

HT --> INFBUS

0

0.93

0

Table 2 Line Data (SMIB)

c.       Transformer Data:

From --> To

R (p.u)

X (p.u)

Tmax

Tmin

MVA Rating

Tstep

LT --> HT

0

0.15

0

0

2220

0

Table 3 Transformer Data (SMIB)

d.      Transient Data:

Generator

MCTYPE

H

Ra

Xd

X'd

X''d

T'd0

T''do

Xl

Xq

X'q

X''q

T'q0

T''q0

KD

INFGEN

0

99999

0

0

0.0001

0.00001

0

0

0

0

0

0

0

0

0

LTGEN

2

3.5

0.003

1.81

0.3

0.23

8

0.03

0.15

1.76

0.65

0.25

1

0.07

0

Table 4 Transient Data (SMIB)

MCTYPE = 0, the machine model is Classical.

MCTYPE = 1, the machine model is Transient (i.e. Two-Axis Transient model with variable voltages E’d and E’q behind transient reactances X’q and X’d)

MCTYPE =2, the machine model is Sub-Transient (i.e. Two-Axis-Sub-transient Model with variable voltages E”q and E”d behind sub-transient reactances X”d and X”q)

e.      Excitation System - 1 Data:

Generator

TR

TA

TE

TF

KA

KF

KE

EFDMAX

EFDMIN

AEX

BEX

LTGEN

0.015

0.0001

0.0001

0.0001

200

0

1

7

-6.4

0

0

Table 5 Transient Data (SMIB)

The excitation system used for the generator is IEEE Type 1 excitation system.

3.       Disturbance Scenario and Events

Maximum time of Simulation = 3.8 s

Step size = 1 ms

Simulation events for this system are set up as follows: 

i.         3-Phase Fault at the end of LIN2 (near HT) at t = 1 

ii.       Clearing fault at t = 1.06 seconds by opening LIN2

 

Figure 2 Load Flow results for SMIB using PowerApps

 

4.       Simulation Result Comparisons with the SMIB Benchmark System

In these studies, the generator absolute rotor angle, active power output, exciter output voltage and terminal voltage responses of LTGEN with different AVR's will be investigated following the simulation events. Different plots showing the generator absolute rotor angle, Active power output, exciter output voltage and terminal voltage simulation results by PowerApps and the SMIB Benchmark System as published [2]. 

 

a.       Study 1 (IEEE Type 1)

Text Box:  Figure 3: Excitation System - 1     

Generator

TR

TA

TE

TF

KA

KF

KE

EFDMAX

EFDMIN

AEX

BEX

LTGEN

0.015

0.0001

0.0001

0.0001

200

0

1

7

-6.4

0

0

Table 6 Excitation System - 1 Data (SMIB)

 

b.      Study 2 (IEEE Type 2)

Text Box:  Figure 4: Excitation System - 2

Generator

TR

TA

TE

TF1

TF2

TF3

KA

KE

KF

EFDMAX

EFDMIN

AEX

BEX

LTGEN

0.015

0.0001

0.0001

0.0001

0

0

200

0

1

7

-6.4

0

0

Table 7 Excitation System - 2 Data (SMIB)

 

c.       Study 3 (IEEE Type 4)

Text Box:  Figure 5: Excitation System - 4

Generator

TR

TA

TB

TC

KA

KC

VIMIN

VIMAX

VRMIN

VRMAX

LTGEN

0.015

0.0001

0.0001

0.0001

200

0

-10

10

7

-6.4

Table 8 Excitation System - 4 Data (SMIB)

 

d.      Study 4 (IEEE Type 5)

Text Box:  Figure 6: Excitation System - 5

Generator

TR

TA

TE

TF1

TF2

TF3

KA

KE

KF

EFDMAX

EFDMIN

AEX

BEX

LTGEN

0.015

0.0001

0.0001

0.0001

0

0

200

0

1

7

-6.4

0

0

Table 9 Excitation System - 5 Data (SMIB)

Figure 7 Exciter Output voltage Response from SMIB benchmark

Text Box:  Figure 8: Exciter Output voltage response for different excitation systems from PowerApps

Figure 9 Generator Active Power Output Response from SMIB benchmark

Text Box:  Figure 10: Generator Active Power Output response for different excitation systems from PowerApps

Figure 11 Generator Relative Rotor Angle Responses from SMIB benchmark

Text Box:  Figure 12: Generator Relative Rotor Angle Responses for different excitation systems from PowerApps

Figure 13 Generator terminal voltage Response from SMIB benchmark

Text Box:  Figure 14: Generator terminal voltage Response for different excitation systems from PowerApps

The generator rotor angle, exciter output voltage, terminal voltage and active power output are compared in figures 7 to 14. Note that there are some minor differences between the responses obtained from PowerApps and SMIB benchmark. These differences can be attributed to the fact that critical clearing time for the SMIB benchmark [2] is 0.07 seconds (fault cleared at 1.07 seconds). However in PowerApps, fault is cleared at 1.06 seconds to obtain a matching response. The reason is that the SMIB benchmark example models synchronous machine saturation resulting in optimistic solution for synchronous machine. PowerApps does not model the same. Another reason for differences can be due to differences in excitation system approximation.

5.       Conclusion

The PowerApps Transient Stability generated simulation results for the generator rotor angle, exciter output voltage, active power output, and terminal voltage in studies performed have some minor differences between the responses obtained. These differences can be due differences in fault clearing time, generator models and excitation system models.

References:

1.       P.M. Anderson and A.A. Fouad, “Power System Control and Stability”, 2nd Edition, John Wiley & Sons, Inc., Publication, 2003.

2.       Prabha Kundur, “Power System Stability and Control”, McGraw Hill, Inc., 1994.

3.      IEEE Recommended Practice for Excitation System Models for Power System Stability Studies, IEEE Std 421.5™-2005 (Revision of IEEE Std 421.5-1992).


http://powerapps.org/PAES_TStability.aspx


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