This document discusses a detailed electromechanical model of a DFIG-based wind turbine connected to a power grid. It aims to regulate the pitch angle at variable wind speeds, maintain the DC-link voltage, and analyze faults in a PMSG-based wind energy conversion system. It provides background on DFIG technology, reviews various control schemes, and presents simulation results analyzing the performance of the DFIG at constant and variable wind speeds.

1. DFIG-Based Wind Power Conversion
System Connected To Grid
UNDER THE GUIDENACE OF
PROF.SUNIL KUMAR P
ASST PROF
DEPT OF EEE

2. Outline of Presentation
⚫ Objective
⚫ Introduction
⚫ Literature Review
⚫ Control Schemes
⚫ Simulation Results
⚫ Conclusions
⚫ Future scope of the work

3. OBJECTIVE
A detailed electromechanical model of a DFIG-based wind
turbine connected to power grid is studied.
Aim of thesis is to :
► Regulate Pitch Angle at variable wind speed
► Maintain DC-link Voltage
► Fault analysis of PMSG based Wind Energy Conversion
System

4. INTRODUCTION
► Wind generation has become the most important alternate
energy source and has experienced increased progress in
INDIA during the past decade.
► Wind energy conversion system suffer from the fact that their
real power generation is closely dependent on the local
environmental conditions.

5. Contd…
► DFIG based wind turbine with variable-speed, variable-pitch
control scheme is the most popular wind power generation.
► This machine can be operated either in grid connected or
standalone mode.
► In this thesis, DFIG is operated with different sub-systems in
the MATLAB/SIMULINK environment. Steady state behavior
of the wind turbine system is presented and analyzed.

6. Wind Power Generation: Working
Principle

7. VARIABLE SPEED DIRECT DRIVE
WIND ENERGY CONVERSION
SYSTEM
absorbs the
► In variable speed systems, the turbines rotor
mechanical power fluctuations by changing its speed.
► To allow variable speed operation, the mechanical rotor
speed and the electrical frequency of the grid must be decoupled.
► So the output power curve is smoother which greatly enhances the
quality of power.
► However, since variable speed operation produces a variable
frequency voltage, a power electronic converter must be used to
connect to the constant frequency grid

8. Types of Generators
► Induction generators
► Synchronous generators
► Doubly fed induction generators

9. Squirrel cage induction generator
► Conventional, directly grid coupled squirrel cage induction
generator.
► This wind turbine is normally referred to as a constant
speed or fixed speed wind turbine
► A SCIG always consumes reactive power. In most cases, t
his is undesirable, particularly in case of large turbines a
nd weak grids.
► Reactive power consumption of the SCIG is nearly always
partly or fully compensated by capacitors in order to achiev
e a power factor close to one.

10. Squirrel cage induction generator

11. Doubly Fed Induction Generator
► The stator is directly connected to the grid, and the rotor
is connected to the grid through a partial scale power
electronic converter.
► High torque peaks in the machine and large stator peak
currents under grid fault conditions depending on control
► Regular maintenance of the brush-slip ring set to bring
power to the rotor
► External synchronization circuit required between the
stator and the grid to limit the start-up current
► In the case of grid disturbances, ride-through capability of
DFIG is required so that the control strategies may be
very complex.

12. Doubly Fed Induction Generator

13. Synchronous Generator
► The permanent magnet synchronous generator (PMSG)
is excited by a permanent magnet.
► The PMSG is connected to the grid through a full-scale
power electronic converter.

14. Synchronous Generator

15. Literature Review
► In Holdsworth et al [18], the modeling and control strategies
of fixed speed and doubly-fed asynchronous generator wind
turbines have been described and their performance were
compared during power system disturbances
► In Pena et al [19], the DFIG working with a Scherbius
scheme, consisting of two back-to-back PWM converters,
has been presented. An experimental transputer controlled
system has been described, and the fundamental
operational advantages have been verified.

16. Contd..
► Yuanye Xia et al [2011], presented a technique for maximum power
point tracking by using Perturbation and observation to eliminate the
effect of fluctuation wind conditions.
► Ribeiro et al [17], presented energy storage system for advanced
power application. The potential performance benefits produced by
advanced energy storage applications are improved system reliability,
dynamic stability, enhanced power quality, transmission capacity
enhancement, and area protection. An energy storage device can also
have a positive cost and environmental impact by reducing fuel
consumption and emissions through reduced line losses and reduced
generation availability for frequency stabilization.

17. Contd..
► Morel et al [25], presented a new system for variable speed using
a doubly-fed induction machine. In this case, power can reach
only 20% of the maximum mechanical power as compared with
classical one.
► In Datta and Ranganathan [27], in this paper, a method of
tracking the peak power in a wind energy conversion system
(WECS) is proposed, which is independent of the turbine
parameters and air density. The criteria for selecting the critical
control parameters are described. The algorithm is implemented
on a laboratory setup using a grid-connected wound rotor
induction generator controlled from the rotor side

18. DFIG-based wind energy conversion
system

19. BACK TO BACK CONNECTED POWER CONVERTER BRIDGES
Two power converter bridges connected back-to-back by means of a dc link can
accommodate the power flow in a DFIG.
The purpose of the grid side converter is to maintain the dc link voltage constant.
It has control over the active and reactive power transfer between the rotor and the grid.
The machine side converter is responsible for control of the flux, and thus, the active
and reactive powers .
ADVANTAGES:
⮚Less cost of AC-AC converter.
⮚Improved system efficiency.

20. Power Converter Controls
The control sequences are as follows:
a)Measurement of all required quantities including machine voltage, machine
and grid currents, and machine angle.
b) Extraction of the voltage angle using a phase-locked loop (PLL)
c)To perform the appropriate transformations to express all voltage and current
quantities on the synchronously rotating frame
d) Calculation of active power and reactive power.
e)To generate the machine Current references using the output of the PI
compensator
f) Machine Current control using PI compensators for d and q axes
components
g) Transforming the machine voltage back to abc quantities
h) Modulation of the machine voltages for generation of the gating signals

21. Control
► Pitch control requires active control systems to turn the blades
► Nowadays stall control is mainly used in constant speed turbines, whereas
► Pitch control is used in variable speed turbines.

22. Pitch angle controller

23. Simulation model of Buck-boost
converter in DC-link of DFIG

24. Performance of DFIG at constant Wind speed (15m/s)

26. Simulink Model of DFIG

27. Performance of DFIG at Variable Wind speeds

29. PARAMETERS OF DFIG
Rated Power 10[MW]
Rated Voltage 575[kv]
No. of Phases 3
Configuration Sinusoidal
Flux linkage 1.48 [V.s]
Frequency 50[hz]
No. of pole pairs 3
Stator Resistance 0.00706 [pu]
Stator Inductance [Ld] 1.9e-3[pu]
Stator Inductance [Lq] 1.6e-3[pu]

30. CONCLUSION
► Following results are achieved in this project:
► DFIG is able to control the power at variable wind
► DC link voltage was regulated
► MPPT using Pitch angle control at variable wind is achieved

31. Future Scope
The following problems can be taken in future:
►To improve the existing control for controlling the DFIG for
voltage regulation.
►To reduce the cost of this machine whether by reducing the
numbers of switching devise, or other devices.
►Also reducing the size of wind energy conversion system.

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38. Thank You !!!