# SINDHU.C.MANOHARAN Edited By Sarath S Nair

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SINDHU.C.MANOHARAN Edited By Sarath S Nair www.technologyfuturae.com
MODELING OF THE WIND TURBINE WITH A PERMANENT MAGNET SYNCHRONOUS GENERATOR SINDHU.C.MANOHARAN Edited By Sarath S Nair

CONTENTS Introduction How does a wind turbine work
Model of wind turbine with PMSG Different types of PMSG Constructional features Modeling of generator Voltage and torque equation Permanent Magnet Synchronous Generator Control schemes of a permanent magnet (PM) generator AC-DC-AC Power Conversion System Conclusion

INTRODUCTION Wind energy is one of the best technologies available today to provide a sustainable supply to the world development. In terms of the generators for wind-power application, there are different types of wind turbine are there, fixed-speed wind turbines and variable speed wind turbine In fixed speed wind turbine, induction generators are used (application in wind farms). But the limitations of such generators are low efficiency and poor power quality In variable speed wind turbine, doubly fed induction generators and permanent magnetic synchronous generators are used.

HOW DOES A WIND TURBINE WORK

MODEL OF WIND TURBINE WITH PMSG
VSC1=machine side power converter T1=interface transformer L1=inductance of the transformer Ug=Output voltage of VSC1 fg=electric frequency

DIFFERENT TYPES OF PMSG
Radial flux permanent magnet machine (RFPM) Axial flux permanent magnet machine (AFPM) Transverse flux permanent magnet machine (TFPM)

RFPM machines The RFPM machine is producing the magnetic flux in the radial direction with PMs which are radial oriented. It is the best choice for direct drive wind turbine AFPM machines The AFPM machine is a machine producing magnetic flux in the axial direction with permanent magnets. (application in low speed low power range) TFPM machines The transverse flux (TF) principle means that the path of the magnetic flux is perpendicular to the direction of the rotor rotation.

CONSTRUCTION OF PMSG Stator is composed by teeth formed by silicon iron sheets These teeth are fixed by 2 bronze disks in their end. Skewing is provided to avoid cogging torque

PRINCIPAL PARTS OF GENERATOR

PERMANENT MAGNET SYNCHRONOUS GENERATOR
Voltage for a PM generator in the d-q axis synchronous rotational reference frame can be expressed as

GENERATOR MODEL The dynamic model of PMSG is derived from two phase synchronous reference frame ,in which q axis is 90 ahead of d axis with respect to the direction of rotation

GENERATOR MODEL (cont’d)
The electrical model of PMSG in the synchronous reference frame is Rs =stator resistance Ld and Lq=inductance of the generator on d and q axis Lld and Llq=leakage inductance of generator on d and q axis We=electrical rotating speed(=Np Wg)

GENERATOR MODEL (cont’d)
Ld=Lds+ Lqs then equation becomes We assume Ld=Lq=L then equation becomes

GENERATOR MODEL (cont’d)
ed=0 eq=we Apply in above equation we will get equivalent circuit as

Which shows Torque can be regulated by current through q axis
TORQUE EQUATION As the inductance of d and q axis are equal the torque can be expressed as follows… Which shows Torque can be regulated by current through q axis

CONTROL STRATEGY OF WIND TURBINE
Pitch control strategy Yaw control

DESIGN SPECIFICATION OF PMSG
Rated power = 2MW; Rated wind speed = 12m/s; Resistance: Ra =.1Ohm; Inductance: L =0.005H; Gear ratio: ng =77; Number of pole pairs: np =2; Radius of wind turbine rotor: R=41m; Equivalent inertia: J=8000kg.m2;

AC-DC-AC POWER CONVERSION SYSTEM
The amplitude and frequency of the output voltage are not constant due to the variable speed and fixed excitation of the permanent magnets. 3-phase diode rectifier is used for the AC/DC conversion. The SPWM (sinusoidal pulse width modulated) inverter with filter is adapted for the DC/AC power conversion. The PIC microcontroller combined with dedicated SA4828 chip is adopted to control of the SPWM inverter for a 20kW direct driven PM generator wind power generation system.

SUMMARY The complete model of the variable speed wind turbine with PMSG that is scheduled to connect AC grid is discussed The design characteristics Constructional features of PMSG is discussed The control strategy for AC/DC/AC power conversion of the PM generator are also discussed

REFERENCE Magnet Synchronous Generator for Integration”
[1] E. Muljadi, S. Drouilhet, R. Holz and V. Gevorgian, "Analysis of permanent magnet generator for wind power battery charging,“ IEEE-IAS Annual Meeting, vol.1 , Oct ,pp [2] A. J. G. Westlake, J. R. Bumby, and E. Spooner, "Damping the power-angle oscillations of a permanent-magnet synchronous generator with particular reference to wind applications," IEE Proc.- Electr. Power Appl, Vol. 143, No. 3, May 1996, pp [3] Ozdemir Gol’ and Bijan Sobhi-Najafabadi, “Use of Impedance Models in Permanent Magnet Synchronous Generator Design” [4] Ming Yin, “Modeling of the Wind Turbine with a Permanent Magnet Synchronous Generator for Integration” [5] Rogel R. Wallace,Thomas A. Lipo, Luis A. Moran,Juan A. Tapia:Design and Construction of a Permanent Magnet Axial Flux Synchronous Generatorin Proc. IEEE PESC’90, San Antonio, TX, USA, vol. 1, pp. 325~332, Jun

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