Modeling and Analysis of Double Fed Induction

8/12/2019 Modeling and Analysis of Double Fed Induction

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above equations, the steady state equivalent circuit of DFIGdrawn as shown in figure. (2)

Figur2. Steady state equivalent circuit of DFIG

IV. FLOWCHARTOFDFIGOPERATIONA. POWER FLOW DIAGRAM

Figur3. Sub synchronous speed

Figure4. Super synchronous speed

B. FLOW CHARTThe DFIG d-q model was simulated usingMATLAB/SIMULINK in both generating and motoring modeof operation with vector control strategy and favorable fortransient condition. The machine modeled in vectorized

synchronous reference frame. The choice of synchronousreference frame makes it particularly for the simulation ofDFIG in transient condition. D- axis is aligned with the statorspace voltage vector than injected rotor voltages are derivedfrom PI controller which can control reactive and active powerand deliver to grid. With wind turbine speed then the machinerepresented as motoring mode when electromagnetic torque(Tem), stator active (Ps) and reactive power (Qs), wind turbinetorque (Te) are negative with Wm


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Figure6. Vector control strategy of DFIG

V. SIMULATIONRESULTSThis section illustrates the simulated results of stator and

rotor active power for a step change in turbine torque at

different turbine speeds. The model was simulated using

MATLAB/SIMULINK platform.

A step change in turbine torque is given at t=5sec. Turbine

torque controls the stator active power. Hence a step change in

turbine torque results in change in stator active power which is

shown in Fig (8)

Fig (9) shows a step change in reference reactive power which

results in change in stator and rotor currents in fig (10), fig(11).

Figure7. Change in electromagnetic torque (Te) with sudden step change inturbine torque.

Figure8. Change in Ps with sudden step change in turbine torque

Figure9.Change in Qs with sudden step change in reference reactive

Figure10.stator current Isd and Isq

Figure11.Rotor current Ird and Irq

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From the Fig (13) at sub synchronous speeds the powergiven to the shaft is (1-s)*P and the stator power is alwaysP.so remaining sP power is fed from the rotor. So rotorpower is positive in this case

From the fig (13) at super synchronous speed shaft power is(1+s)P.in this case stator power P is fed to grid andremaining sP is fed to grid through rotor .so in this case Pris Zero as shaft power is P

Ird varies with the change in the torque i.e. changes withchange in active power requirement.it is constant for particularvalue of load at any speed. Similarly Irq varies with the changein the reactive power requirement .it is also constant at anyspeed

Finally , stator active power and reactive power remainssame ( acts as a generator) under different speedsi.e.subsynchronous, supersynchronous speeds. But rotor activepower changes depends upon wind turbine speeds.

VI. CONCLUSIONSIn this paper contribution, the induction machine is modeled in

vectorized form in the synchronous frame. This model can be

applicable for all types of induction generator configurations

for steady state and transient analysis. However the choice of

the reference frame will affect the simulation speed and in

certain case the accuracy of results. In this model, the d-axis is

aligned with stator space voltage vector. The injected rotor

voltages (at slip frequency) are derived from PI controlled that

regulate the active and reactive powers delivered by the

generator. In addition, vector control strategy has been

examined for controlling active and reactive power of grid,

stator and rotor sides. The behavior of the system was

investigated during step change in wind speed i.e.

subsynchronous, synchronous and supersynchronous speeds.From the results it was observed that, stator active remains

same (delivers active power to grid) under all speeds. But,

rotor active power absorbs or delivers under sub or super

synchronous speeds respectively.

REFERENCES

[1] S. Muller, M. Deicke and R.W. De Doncker, "Doubly fed inductiongenerator systems for wind turbine", IEEE Industry ApplicationsMagazine, Vol.8, No. 3, 2002, pp. 26-33.

[2] A.Tapia, G.Ostolaza and J.X. Saenz, "Modeling and control of a windturbine driven doubly fed induction generator", IEEE Transactions on

Energy Conversion, Vol. 18, June 2003, pp. 194- 204.

[3] Lucian Mihet-Popa, Frede Blaabrierg, Wind Turbine GeneratorModeling and Simulation Where Rotational Speed is the ControlledVariable, IEEE Transactions on Industry Applications, Vol. 40 No.1,January/February 2004.

[4] Andrew Miller, Edward Mulijadi, Donald S. Zinger, A Variable SpeedWind Turbine Power Control IEEE Transactions on EnergyConversion,vol.12, no.2, June 1997.

[5] Shuhui Li,A Simulation Analysis of Double Fed Induction Generatorfor Wind Energy Conversion Using PSpice IEEE Power EngineeringSociety General Meeting, 18-22 June 2006.

[6] S.J. Chapman, Electric Machinery Fundamentals, New York: TheMcGraw-Hill Companies, 1999.

[7] R. Pena, J. C. Clare and G. M. Asher, "Doubly fed induction generatorusing back-to-back PWM converts and its application to variable speedwind-energy generation", IEE Proceedings Electrical Power

Application, Vol. 143, No.3, pp. 231-241, May 1996.

[8] B.Chitti Babu, K.B.Mohanty and C.Poongothai, Performance ofDouble-Output Induction Generator for Wind Energy ConversionSystems, Proceeding of IEEE, 2008,pp.933-938.

[9] J.G. Slootweg, H. Polinder and W.L. Kling Dynamic Modeling of aWind Turbine with Doubly Fed Induction Generator, Proceedings of

IEEE 2001.

[10] B.H.Chowary, Srinivas Chellapilla, Doubly-fed induction generator forvariable speed wind power generation Transactions on Electric PowerSystem Research, Vol.76,pp. 786-800, Jan 2006.

[11] Yazhou Lei, Alan Mullane, Gordon Lightbody, and Robert YacaminiModeling of the Wind Turbine With a Doubly Fed Induction Generatorfor Grid Integration Studies IEEE transactions on energy conversion,vol. 21, no. 1, march 2006

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