14 - Parameter Tuning

8/10/2019 14 - Parameter Tuning

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section will investigate the relationship between a parameter of a mode and the model

response process for some typical transfer function models.

3. Tuning of Power System Dynamical Model Parameters

A power system dynamical device usually consists of different types of elements. These

elements can be mathematically presented by some typical dynamical components or

transfer functions. The following describes a number of typical dynamical components inpower system dynamical models, and illustrates how the responses of these components

are affected by varying their parameters. Also, a simplified model of a single generator

power system is investigated in this section.

Inertial Components: Its transfer function is shown as Figure 3.1. The inertial

component is usually used to model the regulator amplifier, governor relay, or

electric/hydraulic converter. Figure 3.1 and 3.2 display the responses of this component

when applying a step input with different time constant and gain values. As can be seenfrom Figure 3.1, the raising rate of response will increase with reducing time constant

value. But the settle down value of response would not be affected by varying timeconstant value. When increasing gain value, as shown in Figure 3.2, both the raising rate

and settle down value of response will be increased.

Figure 3.1 Inertial Component Responses for Changing

Time Constant


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Figure 3.4, when increasing time constant value, the raising rate and overshooting

magnitude of response will increase, but the falling rate during the decay segment will bedecreased, thus, the settle down time of response would last longer. When increasing gain

value, as shown in Figure 3.5, the raising rate and overshooting magnitude of response

also will increase, but the falling rate would not be changed.

Figure 3.4 Inertial-Differential Component Responses for

Changing Time Constant

Figure 3.5 Inertial-Differential Component Responses for

Changing Gain

Single Generator Power System Model: Figure 3.6 shows a simplified model of a

single generator power system. The block Ks and Kd are defined as system synchronizing


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coefficient and system damping coefficient, respectively. These two coefficients

represent the equivalent effects of generator, AVR, governor, loads and other systemcomponents. Figures from 3.7 to 3.12 display the power angle and speed responses of the

power system model when a load shed is applied with different model parameters. As can

be seen from Figure 3.7 and 3.8, when increasing damping coefficient Kd, the oscillation

magnitudes of power angle and speed responses will be reduced, but the oscillationfrequency of them is not changed. When increasing synchronizing coefficient Ks, as

shown in Figure 3.9 and 3.10, the oscillation magnitudes of power angle and speed

responses will be reduced and the oscillation frequency of them will be increased. Also, itis found that the initial power angle becomes smaller with increasing Ks. When reducing

generator inertial coefficient H, as shown in Figure 3.11 and 3.12, the raising rate,

overshooting magnitude and oscillation frequency of speed response will be increased,but settle down time becomes shorter. For the power angle response, its falling rate, and

oscillation frequency will be increased, but its undershooting magnitude will be

decreased and settle down time also becomes shorter.

Figure 3.6 Simplified Single Generator Power System Model


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Figure 3.7 Generator Speed Responses for Changing

Damping Coefficient

Figure 3.8 Generator Power Angle Responses for Changing

Damping Coefficient


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Synchronizing Coefficient


Synchronizing Coefficient


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Inertial Coefficient


Inertial Coefficient

4. Examples of Tuning Power System Dynamical Model Parameters

In this section, some examples are presented to illustrate how to tune the parameters of

power system dynamical models utilizing the site test or system incidence recording data,so as to make the responses of dynamical model match the real recording data.

4.1Generator Start-up Case

This is a real test case. The test system, as shown in Figure 4.1, is a Hydro GenerationStation as the backup power system of a Nuclear Power Plant. The test process includes:


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first start a generator unit, at the same time flash the generator field winding, when

generator terminal voltage reaches approximately 70% to 90% of rated output voltage,then a voltage relay trips the appropriate circuit breakers and connect the emergency load

from the nuclear generation plant to the generator. The generator AVR and governor

models are shown as Figure 4.2 and 4.3. The typical parameters of the models are listed

in Table 4.1 and 4.2. When using the typical parameters in simulation study, as can beseen from Figures 4.4, 4.6, 4.8 and 4.10, the responses of generator speed, voltage, power

and field voltage do not match the site test results. By investigating the response curves,

obviously, some transfer function time constants and gains of both AVR and governormodels and the generator damping and inertial coefficients need to be tuned up properly.

A set of modified model parameters are listed in Table 4.1 and 4.2. The responses of the

system corresponding to the parameter modifications show a very good match to the sitetest results as displayed in Figures 4.5, 4.7, 4.9 and 4.11. In this project study, it is

discovered that the response of the motor start simulation will not correctly express the

real situation if the formula coefficients of motor load model are not presented properly.

The formula coefficients of motor load model usually can be obtained by using curve

fitting technology based on the load torque curve. In most cases, the manufacturers onlyprovide the load torque curves under the speed range from 0 to 100%. It is no problem to

simulate the motor start if the system frequency within this speed range. Otherwise, thesimulation results will not truly reflect the actual situations. In this test case, the generator

speed ever overshoots to 120% of rated speed at a period of time. Figure 4.13 shows the

response of a motor electrical power during start up have big discrepancy against the sitetest result when using the load model with the speed range from 0 to 100%. When

remodeling the load torque curve covered the speed range to 120% as given in Figure

4.12, the response of the motor electrical power corresponding to the modified loadmodel shows a very good match to site test results as shown in Figure 4.14.


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KGEN 2 KGEN 1

W/OMod#2

4kV B1TS

600V LC 3X4 600V LC 3X8

4kV 3TC

TX-3X5

HP IP -3A600 HP

LP IP -3A400 HP

RBSP-3 A250 HP

LPSWP- 3A600 HP

TX-3X8

MCC 3XS1

3EPTC13

3PTC3

3TC/D/E-3B1T

3TC-3B1T

3TD/E-3B1T

3TC-3B2T

NO

B1TS-3B1T

3X5 Test 13X8 Test 1 3X8 Test 23X4 Test 23X4 Test 1

TX-3X4

13. 2kV Keo#113. 2kV Keo#2

U3 4kV bus13

CT4

Underground

NO

4kV B2TS

4kV 3TE4kV 3TD

600V LC 3X10600V LC 3X6600V LC 3X5 600V LC 3X9

TX-3X9 TX-3X6 TX- 3X10

MCC 3XS2

LP IP -3B400 HP

RBSP-3 B250 HP

LPSWP-3B600 HP

HPIP-3B600 HP

3EPTE123PTE3

MCC 3XS3

3PTD3 3EPTD13

3TD-3B1T

3TE-3 B1T3TC/D/E-3B2T

3TD-3B2T

3TE-3B2T

3TD/E-3B2T

NO

B2TS-3B2T

3X5 Test 23X6 Test 1 3X6 Test 23X9 Test 1 3X9 Test 2

EFDWP- 3A600 HP

EFDWP- 3B600 HP

HP IP -3C600 HP

Figure 4.1 Test System for Generator Start-up

Figure 4.2 Exciter/AVR Model Diagram of Hydraulic Generator


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Parameter Typical Tuned

RC 0.0 0.0

XC 0.03 0.03

TR 0.0 0.0

TC 0.0 0.0

TBB 0.0 0.0

KA 100 70

TA 0.02 0.02KF 0.5 0.12

TF 0.5 0.8

KC 0.1 0.1

VVLR 1.07 1.07

KVL 120.0 120.0

TVL 0.05 0.05

KVF 1.0 1.0

TH 0.05 0.05

VImax 0.17 0.17

VImin -0.17 -0.17

VRmax 3.66 3.66

VRmin 0.0 0.0

Vdc 125 125

Rf 0.15 0.06VHZ 0.74 0.74

TD 2.5 2.5

Vfb 87.5 87.5

Ifb 585 585

Vref 1.025 1.025

Table 4.1 Typical and Tuned Parameters of Exciter Model

Figure 4.3 Governor Model Diagram of Hydraulic Generator

Parameter TP Q GC TG RP RT TR H D

Typical 0.04 1 2.5 1 0.02 0.4 5.5 7 2

Tuned 0.04 1 2.5 1.41 0.02 0.4 7.5 4.94 1.1

Table 4.2 Typical and Tuned Parameters of Governor Model


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Figure 4.4 Comparison between Simulated Generator Speed Response(Using Typical Parameters) and Site Measured Speed

Figure 4.5 Comparison between Simulated Generator Speed Response

(Using Tuned Parameters) and Site Measured Speed


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Figure 4.6 Comparison between Simulated Generator Voltage Response

(Using Typical Parameters) and Site Measured Voltage


(Using Tuned Parameters) and Site Measured Voltage


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Figure 4.8 Comparison between Simulated Generator Electrical Power Response

(Using Typical Parameters) and Site Measured Electrical Power

Figure 4.9 Comparison between Simulated Generator Electrical Power Response

(Using Tuned Parameters) and Site Measured Electrical Power


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Figure 4.10 Comparison between Simulated Generator Field Voltage Response

(Using Typical Parameters) and Site Measured Field Voltage

Figure 4.11 Comparison between Simulated Generator Field Voltage Response

(Using Tuned Parameters) and Site Measured Field Voltage


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Figure 4.12 Induction Motor Load Torque Curve Fitting

Figure 4.13 Comparison between Simulated Induction Motor Electrical Power

Response (Using Typical Parameters) and Site Measured Electrical Power


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Figure 4.15 Test System for Diesel Generator Load Shed

Figure 4.16 Exciter Model Diagram of Diesel Generator


KA 156 240

KC 0.001 0.001

KE 0.08 0.08KF 0.1 0.27

KI 9 9

KP 0.08 0.08

TA 0.05 0.05

TE 1.0 4

TF 3.0 3.0

TR 0.005 0.005

Vrmax 17.5 17.5

Vrmin -15.5 -15.5

Table 4.3 Typical and Tuned Parameters of Exciter Model


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Figure 4.17 Governor Model Diagram of Diesel Generator


Droop 5.0 5.0

ThetaMax 60.0 60.0

ThetaMin 4.0 4.0Alpha 0.04 0.027

Beta 0.02 0.0192

Rho 0.1 0.3

K1 128 119

Tau 0.1 0.09

T1 0.15 0.151

T2 0.12 0.12

H 1.9 1.69

D 4.0 7.0

Table 4.4 Typical and Tuned Parameters of Governor Model


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Figure 4.18 Comparison between Simulated Generator Frequency Response

(Using Typical Parameters) and Site Measured Frequency

Figure 4.19 Comparison between Simulated Generator Frequency Response

(Using Tuned Parameters) and Site Measured Frequency


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(Using Typical Parameters) and Site Measured Voltage


(Using Tuned Parameters) and Site Measured Voltage

4.3Network Short-Circuit Fault Test Case

This test case is to simulate a system response when a short-circuit fault occurred on a

bus. The test system is shown in Figure 4.22. The simulation events include: short-circuitfault occurs at MCC feeder Bus3, voltage relay trips some load at Bus-A and Bus-B when

voltage drops to 50% during the fault, in 0.38 seconds the circuit breaker 52GH is tripped

to disconnect fault point, in 0.8 seconds the circuit breaker 52B4 is tripped to disconnectthe tie link to utility. The actual measured current and voltage of generator G4 and

current at branch 52B4 are displayed in Figure 4.23. The simulation responses of the

system current and voltage for using typical generator parameters listed in Table 4.5 andusing tuned parameters listed in Table 4.5 are shown as Figure 4.24 and 4.25,


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respectively. As can be seen from Figure 4.25, the response of the system current and

voltage using tuned parameters are very close to the actual measured data.

Bus4

Bus- BBus2

Bus1

T3

12. 5 MVA

pump273. 936 kW

pump3937 kW

pump483. 175 kW

CB4

52B4

52GH

LUMP15. 848 MVA

LUMP210. 75 MVA

pump5

345 kW

LUMP34. 458 MVA

CB5

CB6

LUMP410. 75 MVA

3.3 k

3.3 k3.3 kV

65 kV

3.3 kV

Bus-A

Bus3

3.3 kV

Power Gr i d

pump173. 936 kW

G415. 111 MW

Figure 4.22 Test System for Short-Circuit Fault


Xd 1.48 0.75

Xq 1.48 0.74

Xd 0.215 0.15

Xq 0.45 0.16

Xd 0.136 0.12

Xq 0.136 0.13

Td0 7.05 7.05

Tq0 1.0 1.0

Td0 0.042 0.042

Tq0 0.18 0.18

H 5.4 8

D 5 1

Table 4.5 Typical and Tuned Parameters of Generator


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Figure 4.23 Site Voltage and Current Recordings DuringShort-Circuit Fault

Figure 4.24 Simulated Generator Voltage and Current Responses

(Using Typical Parameters)


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Figure 4.25 Simulated Generator Voltage and Current Responses

(Using Tuned Parameters)

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14 - Parameter Tuning