Induction Generator Parameters Effecting Power Quality Biology Essay

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Abstract: Use of Induction Generators (IG) is widely increasing in wind generation. This paper presents the effect on power quality with change in parameters (i.e. rotor resistance, rotor inductance, mutual inductance, stator resistance and stator inductance) of the IG. Simulated results are compared with the experimental results to verify the candor.

Key words - Induction generator, power quality, wind generation.

INTRODUCTION

Recently wind power generation has been experiencing a rapid development in a global scale. Since long, the induction generators has been the mostly used for power generation. To be in the generating mode, the IG should be driven by the turbine at a supersynchronous speed i.e at negative slip. Simulation results for power quality of grid with wind electric generators have been dealt in many Papers[1],[2]. The effect of external parameters such as wind speed, on power quality are given in few research papers[3],[4],[6] -[8], [10] - [12]. Simulated results for the same are presented by various authors. [5] &[9].

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In this paper, a SIMULINK model is developed to study the effect of IG parameters on the power quality. The developed simulink model is first compared with laboratory set up to verify the imminence of laborartry measured results and simulated results. In part II Experimental results and simulated results are compared. Experimental setup developed for the study, a DC motor is used as prime mover for IG. The speed control is done using field control method. For measuring power quality three -phase power quality analizer (model-435, make fluke) is used.

In part-III the SIMULINK model and the simulated results with different generator parameters are presented. Part IV present the analysis of results. Part-V gives the conclusion and recommendation thereof.

EXPERIMENTAL VERIFICATION OF SIMULATED RESULTS

The schematic experimental laborartory setup used to validate the simulated results for IG is shown Fig 1 and the developed simulink model is shown in Fig 2. The L.V. grid is a 415V, 3-phase, 50 Hz source. A Three phase resitive load is shown connected to grid and IG. The IG used in this study is a three phase squarel cage induction generator of 2.2kW. The measured parameter of IG used in this study are:

Stator resistance (Rs) : 4.8Ω per phase

Stator Inductance (Ls) : 0.0303 H per phase

Rotor Resistance (R2') : 3.20 Ω per phase

Rotor Inductance (L2') : 0.0129 H per phase

Mutual Inductance (Lm): 0.3132 H per phase

Fig -1 Schematic laboratory setup

Fig-2 Simulink Model

Fig-3 Active & Reactive power (Experimentally measured)

Fig-3 shows the experimental measured result for active and reactive power at the generator terminals when the operation of induction generator is converted from motoring to generator mode. The measurements were taken 10sec average values.

Fig-4 Active and Reactive Power

Fig-5 shows simulated results of real and reactive powers at generator terminals when machine operation is converted from motoring to generator.

Table -1 shows the comparison of simulated and experimentally measured results

Table-1

Speed in r.p.m.

ExperimentallyMeasured Results

Simulated Results

P

Q

P

Q

1490

201

1686

370

1575

1580

-2368

2678

-2292

2364

Table -2 shows the experimentally measured results and simulated results for current at generator terminals

Table-2

Speed in r.p.m

Experimentally Measured Results

Simulated Results

L1

L2

L3

L1

L2

L3

1490

3

3

2

2.2

2.2

2.2

1580

5

6

5

4.5

4.5

4.5

Table -3 shows the experimentally measured results and simulated results for voltage at generator terminals

Table-3

Speed in r.p.m

Experimentally Measured Results

Simulated Results

L1

L2

L3

L1

L2

L3

1490

412

414

412

414

414

414

1580

413

414

411

414

414

414

The frequency remains fixed and almost negligible variations are recorded in simulated and experimantally measured values.

Table -4 gives the comparison in total harmonics distortion in current and voltage wave of experimentally measured and simulated values when no harmonic is incorporated in simulation model.

Table-4

%

THD

Experimentally Measured Results

Simulated Results

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L1

L2

L3

L1

L2

L3

I

6.98

5.00

6.81

0.09

0.20

0.13

V

2.97

3.40

2.89

0.01

0.01

0.01

The simulated and experimentally measured results show a difference here the reason being the source used in lab contains harmonics distortion. When harmonics distortion is incorporated in the simulation (programable voltage source can be programmed for two harmonics) the there is very small difference between measured and simulated results.The dominant harmonics found in lab measurements are 5th, 7th and 11th. The voltage source when programmed for 5th and 7th gives following results:

Table-5

THD

Experimentally Measured Results

Simulated Results

L1

L2

L3

L1

L2

L3

I

6.98

5.00

6.81

7.7

7.7

7.7

V

2.97

3.40

2.89

8

8

8

This shows that the simulated and experimentally measured results are close in similitude. Hence the developed simulink model is validated and can be further used to study the effect of IG parameters (i.e. rotor resistance, rotor inductance, mutual inductance, stator resistance and stator inductance) on the power quality.

EFFECT ON POWER QUALITY WITH CHANGE IN IG PARAMETERS

(a) Rotor resistance: With the different rotor resistance values; the effect on the power quality parameters is recorded as in table 6, 7 & 8:

Table-6

R2'

Speed in rpm

P

Q

2.8

1490

407

1573

1580

-2604

2566

3.2

1490

365

1575

1580

-2292

2364

4.0

1490

306

1576

1580

-1837

2118

Table 6 shows variation in active and reactive power at different values of rotor resistance.

R2'

%THD (V)

%THD (I)

Speed varies from 1490- 1580 rpm

L1

L2

L3

L1

L2

L3

2.8

19.5

19.5

19.5

15.9

15.9

15.9

3.2

19.5

19.5

19.5

17.3

17.3

17.3

4.0

19.5

19.5

19.5

19.7

19.7

19.7

Table-7

Table -7 gives % total harmonics distortion (voltage and current) for three phases at IG terminals.

Table -8

R2'

Speed varies from 1490- 1650 rpm

%THD (I)

P

Q

L1

L2

L3

3.2

10.8

10.8

10.8

-3948

3898

2.8

9.7

9.7

9.7

-4307

4474

4.0

12.8

12.8

12.8

-3320

3160

Table-8 shows the % total current harmonics distortion and real and reactive power at different values of rotor resistance when the maximum generator speed is 1650 rpm.

The generated frequency, terminal voltage and % voltage harmonics distortion remains unchanged with different rotor resistance values.

(b) Mutual inductance: With the change in mutual inductance the effect on power quality is observed and recorded in table 9 & 10.

Table-9

Lm

P

Q

Speed

1490

1580

1490

1580

0.2132

411

-2003

2115

3015

0.3132

365

-2293

1574

2364

0.4132

351

-2447

1222

2001

Table -9 shows variation in active and reactive power with change in mutual inductance.

Table-10

Lm

%THD (I)

Max. Speed 1580

%THD(I)

Max. Speed 1650

L1

L2

L3

L1

L2

L3

0.2132

14.9

14.9

14.9

10.2

10.2

10.2

0.3132

17.3

17.3

17.3

10.8

10.8

10.8

0.4132

18.7

18.7

18.7

11

11

11

Table -10 shows variation in % THD (current harmonic distortion) with change in mutual inductance and speed.

The generated frequency, terminal voltage and % voltage harmonics distortion remains unchanged at different values of mutual inductance.

(c) Stator Resistance: The effect of change in stator resistance values on power quality is recorded in table 11& 12.

Table -11

Rs

P

Q

Speed

1490

1580

1490

1580

3.8

351

-2294

1581

2302

4.8

365

-2292

1574

2364

5.8

380

-2290

1567

2428

Table -11 shows the variation in active and reactive power with different values of stator resistance values and in when the machine is operating in motoring and generating mode.

Table -12

Rs

%THD (I)

Max. Speed 1580

%THD(I)

Max. Speed 1650

L1

L2

L3

L1

L2

L3

3.8

17.5

17.5

17.5

11

11

11

4.8

17.3

17.3

17.3

10.8

10.8

10.8

5.8

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17.1

17.1

17.1

10.5

10.5

10.5

Table -12 gives effect on %THD (I) at different values of stator resistance and at maximum speed of 1580 and 1650 rpm.

(d) Rotor inductance: The effect of change in rotor reactance on power quality is recorded in table 13 & 14.

Table-13

Lr2'

P

Q

Speed

1490

1580

1490

1580

0.0029

365

-2356

1572

2242

0.0129

365

-2299

1574

2364

0.0229

365

-2217

1576

2475

0.1129

364

-1381

1593

2968

0.2129

361

-719

1612

2887

0.3129

356

-381

1630

2684

Table -13 shows variation in active and reactive power with change in rotor reactance values at two different speeds.

Table-14

Lr2'

%THD(I)

at 1580 r.p.m

%THD(I)

at 1650 r.p.m.

0.0029

22.57

13.8

0.0129

17.36

10.8

0.0229

14.20

9

0.1129

6.37

5

0.2129

4.9

4.4

0.3129

4.4

4.1

Table -14 shows variation in %THD (I) with change in rotor reactance Lr2' at two different speeds.

(e) Stator inductance: The effect of change in stator reactance values on power quality is recorded in table 15 & 16.

Table-15

Ls

P

Q

1580 rpm

1650

rpm

1580

rpm

1650

rpm

0.0303

-2292

-3948

2364

3898

0.1303

-1031

-1146

1953

2760

0.2303

-550

-498

1510

1905

Table -15 gives the variation in active and reactive power with change in stator inductance values at two different running speeds.

Table-16

Ls

%THD(I)

at 1580 r.p.m

%THD(I)

at 1650 r.p.m.

0.0303

17.3

10.8

0.1303

7.3

5.6

0.2303

5.7

4.8

Table -16 gives variation in %THD (I) with change in stator inductance values at two different operating speeds.

RESULT ANALYSIS

The immediacy of experimental results and simulated results show that the SIMULINK model developed for study present analogous results. Firstly, the effect of change in rotor resistance on various power quality parameters such as active power output, reactive power requirements, total harmonics distortion, frequency, voltage etc. are studied. It is observed that with small value of rotor resistance the active power output and reactive power requirements both are increased and %THD (I) is decreased. When the speed is further increased to 1650 rpm the active and reactive power increases but the % THD (I) is decreased. No change is recorded in %THD (V), terminal voltage and frequency as the system is connected to a grid.

If at the same instant load is varied or the load becomes unbalanced the power supplied by the generator remains unchanged as the changed power requirement is fed by the grid. The negative sign in active power indicates that generator is supplying power to the grid/load.

The effect of increase in mutual inductance results increased active power output and decreased reactive power requirements. But %THD (I) is found increased with increase in mutual inductance. Change in stator resistance values give almost negligible effect on the all the power quality parameters. Increases in Rotor inductance reduced the active power output. The reactive power demand is increased but the positive effect is the reduction in %THD (I). Increase in the value of stator inductance gives reduced output power, reduced reactive power and less harmonics distortion.

Conclusion

Analysis of simulated observations as obtained leads to the following major conclusions:

In order to get the increased output active power the R2' L2, & Ls should be low value and Lm value should be high.

For low reactive power requirement values of R2', Lm & Ls should be high. But the value of L2 should be low.

%THD (V), Voltage & frequency remains unchanged with IG parameters.

% THD (I) is less with low value of R2' & Lm and high value of L2 & Ls. Stator resistance is not found effecting the %THD (I).

With the increase in speed active and reactive power increases and % THD (I) is reduced.

It is observed that the generator parameters affect the power quality output of an induction generator. By controlling the generator parameter the power quality can be controlled.

.

Referances:

Nguyen Tung Linh "Power Quality Investigation of Grid Connected Wind Turbines" 978-1-4244-2800-7/09/ $ 25.00 © 2009 IEEE pp-2218-2222

John Olav, Giæver Tande "Applying power quality characteristics of wind turbines for assessing impact on voltage quality" SINTEF Energy Research, N-7465 Trondheim, Norway

V.Vanitha and Dr.N.Devarajan "Effect of Wind Speed Changes on Grid Power Quality at Various Levels of Wind Electric Penetration -A Laboratory Investigation" International Journal of Recent Trends in Engineering, Vol. 1, No. 4, May 2009 pp 8-13.

K.S. Sandhu and Sudhir Sharma "Effects on major power quality issues due to incoming induction generators in power system" ARPN journal of engineering and applied sciences vol.5 no. 2 February 2010 pp- 57-65.

Tomas Petru and Torbjörn Thiringer "Modeling of Wind Turbines for Power System Studies" IEEE transactions on power systems, vol. 17, no. 4, November 2002 pp 1132-1139.

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Marta Molinas,Jon Are Suul,Tore Undeland, "Improved Grid Interface of Induction Generators for Renewable energy by use of STATCOM", IEEE, 2007 ISBN 1- 4244-0632-3/07.

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Garrad Hassan "Study into the Impacts of Increased Levels of Wind Penetration on the Irish Electricity Systems", ESBI, University College, Cork, First Interim report, 2002.

Gordon Randall, Rana Vihauer, Craig Thomson "Characterizing the Effects of High Wind Penetration on a Small Isolated Grid in Arctic Alaska", AWEA's Wind Power Conference, Washington, June 4-7, 2001.

Detlef Schulz, Rolf Hanitsch, Karim Moutawakkil, Christoph Saniter, TU Berlin "Power Quality Behaviour of Large Wind Parks With Variable Speed Wind Energy Converter" 17th International Conference on Electricity Distribution Barcelona, 12-15 May 2003