Modeling of Wind Farm Participation in AGC.

Archana.S.NairS7 EEE

Roll No:39

CONTENTS1. Introduction 2. Wind turbine model3. Generator model4. Set-point control on the variable speed wind generators. A) Set-point tracking using pitch angle control B) Set point tracking using rotor speed control5. Comparative test of PAC and RSC.6. Equivalent wind farm model A) Lumped model B) Aggregated model C) Simplified model D) Simulation of wind farm models7. conclusion 8. References

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INTRODUCTION

Wind power is one of the most rapidly developing renewable energy form in the energy sector.

The common way of modeling the large-scale wind farm is to aggregate simplified wind turbine models.

Both aggregated and simplified wind farm models are developed ,and the simulation results from both wind farm models are presented to show their abilities in depicting the set-point operation under AGC.

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WIND TURBINE MODEL • In the WTG system, turbine blades convert wind energy into

kinetic energy.• By aerodynamic rule, the relationship between wind speed

and turbine power is expressed as,

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• In order to make the WTG operate at MPPT, the set-point signal for a WTG is set as follows,

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wAVpt CP 3),(21

wAVoptpCP 3),0(max,21

WTsp

GENERATOR MODEL

• The electrical part of the variable-speed WTG includes generator and power converter.

• Under normal operation, the transfer function of power converter can be represented by ,

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PsTP WTspa

e

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• Electromagnetic torque from generator side react to mechanical torque by the equation,

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From this,

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is the mechanical power output from the drive train and is the electrical power output at generator side.

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PPsJ emm2

TTsJ emm

PmPe

SET-POINT CONTROL ON THE VARIABLE-SPEED WIND GENERATORS

• There are two ways to regulate the wind energy harvesting.

1) Control the rotating speed of the wind turbine according to its power speed curve, which is called rotor speed control.

2) Control the pitch angle of the turbine blades, which is called pitch control.

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A. SET-POINT TRACKING USING PITCH ANGLE CONTROL

• Pitch angle control (PAC) is an indispensable mechanism in the variable speed WTG for providing power regulations or limiting power output at high wind speed.

• When the WTG is operating at MPPT, different pitch angle would result in different peak power.

• The turbine is controlled by the pitch angle controller and its power output is given as follows,

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• when wind speed is high, pitch angle controller activated to keep WTG producing the desired power.

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wAVoptvpvθ

CP 3),,(max,21

m

Cp versus λ curves under various pitch anglesFig.(1)

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B. SET-POINT TRACKING USING ROTOR SPEED CONTROL

• Rotor speed control (RSC) is to make the most use of inertial response within the WTG when generating the desired electrical power.

• Due to the variation of wind speed, mechanical power does not always match electrical power .• Wind speed increases, .The excessive kinetic

energy produced from the wind turbine would be stored into the inertia by accelerating the rotor speed.

• When , kinetic energy would be released from the moment of inertia to make up for the insufficient power and result in reduction of rotor speed.

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Pm PePP em

PP em

Operating states of the set-point tracking and MPPTFig.(2)

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COMPARATIVE TEST OF PAC AND RSCFig.(3)

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EQIVALENT WIND FARM MODEL

• When wind farm is under AGC, the wind farm side controller distributes grid’s command into individual set-points for WTGs to produce the desired power.

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A. LUMPED MODEL• The active power output of a large scale wind farm is

represented by lumped wind turbine model as,

(7) The use (7) of should be aware of the following assumptions, 1) The average wind speed is specified at the center of the wind

farm.2) Wind turbulence is neglected.3) should remain the same for all WTGs.

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eqVnApCP 3)(),(21

wf

),( C p

B. AGGREGATED MODEL

• The clustering effect of wind turbines, the active power produced by a large scale wind farm is ,

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• With individual wind speeds and set-point information, this model certainly can portray the active power dynamics as well as stability condition at each WTG.

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WTGjPPWF

C. SIMPLIFIED MODEL

• Here keep the wind speeds that are measured within the wind farm and neglect inertial effect on the wind farm output.

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1),0(max,21

basem,3AVpCP

SIMPLIFIED WIND FARM MODELFig.(4)

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D. SIMULATION OF WIND FARM MODELS

• Conduct a wind farm test using the aggregated model and simplified model.

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SIMULATION TESTFig.(5)

WIND FARM MODEL TEST USING PAC

WIND FARM MODEL TEST USING RSC

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COMPARISON OF EXECUTION TIME

Execution time of the aggregated model(sec)

Execution time of the simplified model(sec)

PAC Strategy 857.19 50.42

RSC Strategy 425.95 23.57

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CONCLUSION

• Essentials of wind participation in AGC are raised for discussion by looking through the mechanism of RSC and PAC.

• The simplified wind farm model not only can perform MPPT operation but also can allow any type of set-point assignment.

• Simplified model is able to mimic the wind farm dynamics with great reduction in computation time.

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REFERENCES• Le- Ren Chang- Chien, Senior Member

IEEE,Chih-Che Sun,and Yu- Ju Yeh, “Modeling of Wind Farm Participation in AGC”.IEEE Trans. on power syst. Vol.29,No.3,May2014.

• V.K Mehtha , “Power System”• http://www.researchgate.net/publication/

3213614_Automatic_Generation_Control_of_a_Wind_Farm_with_Variable_Speed_Wind_Turbines.

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THANK YOU

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