Wind turbines are complex machines that are remotely installed and subject to faults. Fault tolerance is important to reduce maintenance costs and increase energy production. This document discusses methods to improve wind turbine reliability through fault diagnosis and fault-tolerant control systems. It describes analyzing faults through model partitioning and propagation, then detecting faults using hardware redundancy, plausibility tests, and model-based approaches. Fault-tolerant control methods presented include signal correction and active/passive linear parameter varying control. Further research is needed to develop integrated online fault detection and fault-tolerant control systems.

1. Fault Tolerance in Wind Turbines
Presented by:
Nitin Goyal

2. Introduction
• Among the renewable energy sources available today, wind power
is the world's fastest growing [Wind Energy News, 2011].
• cheap, inexhaustible, widely-distributed, clean, and climate friendly
• A wind turbine obtains its power input by converting the force of
the wind into a torque (turning force) acting on the rotor blades.
• The amount of energy which the wind transfers to the rotor
depends on the density of the air, the rotor area, and the wind
speed.

3. Need for Fault-Tolerance and Benefits ?
• Wind Turbines are Heavy, Complex and Remotely installed
• Driven by Stochastic wind disturbances, gravitational & gyroscopic
loads.
• Aerodynamic of wind turbines is non-linear, unsteady and complex.
• Prevent catastrophic failures and faults deteriorating other parts of
the wind turbine by early fault detection and accommodation.
• Reduce maintenance costs, Provide diagnostic details to the
maintenance staff by remote diagnosis and Increase Energy
production.

4. Project Scope
• Study of Methods which can improve the Reliability of Wind
Turbines
• Study of application-specific methods for model-based fault
diagnosis and fault-tolerant control.
• Study of design of fault-tolerant control systems and fault
Diagnosis System

5. Design: Horizontal Axis Wind Turbine
• Anemometer is used to measure the
wind speed
• Gearbox connects the low-speed shaft
to the high-speed shaft
• Generator converts rotational energy
into electric energy
• Wind vane is used to measure the
direction of the wind
• Yaw mechanism uses electrical motors
to orient the wind turbine rotor
perpendicular to the direction of the
wind.

6. General Control Strategy
• wind turbines operate
along a certain trajectory
• Wind speed below the
Vw,cut-in, the wind turbine
does not produce any
energy.
• Similarly, wind turbine
does not produce any
energy if wind speed
exceed the Vw,cut-out

7. Fault Analysis

8. Fault Analysis
• Model Partitioning: Model is divided into sub-models suitable for
analysis and identification of the possible component faults in each
subsystem.
• Fault Propagation Analysis: propagates the component faults through the
system and determines their end-effects at system level.
• Fault Assessment: Identification of faults by determining their
occurrence and their impact on the performance of the wind turbine
control system.
• Structural Analysis: Determines analytical redundancy relations in the
system and determines the detectable faults.
• Fault Specification: The fault specification specifies the dynamics of the
faults identified in the fault assessment.
• Remedial Action Selection: The remedial action selection determines the
action that must be taken to stop the propagation of the faults..

9. Fault Detection
There are four types of fault detection schemes:
• hardware redundancy: reconstruction of the process components using
the identical (redundant) hardware components
• plausibility test:check of some simple physical laws under which a
process component works. On the assumption that a fault will lead to
the loss of the plausibility
• Signal-based approaches:process signals that carries information about
the faults of interest and this information is presented in form of
symptoms
• model-based approaches:process model which is implemented in the
software form on a computer

10. Possible Faults in Wind Turbine Controller

11. Fault Diagnosis
• Used for condition monitoring purposes
• provide sufficient information to the supervisor controller to
reconfigure the controller[Active Fault tolerant control].
Fault vector f(k)
fault-corrected state estimate, 𝑥(k)
additional states introduced by faults,𝑥 𝑓(k)

12. Fault tolerant Control
• Fault tolerant control by Signal Correction.
• Active and Passive Fault-Tolerant LPV (Linear
Parameter-Varying)

13. Fault tolerant control by Signal Correction
• Inputs and outputs of the controller are corrected according to
the estimated faults
• can be implemented independent of the structure of the nominal
controller, without affecting the nominal performance of the
controller.
• nominal controller is not modified itself, only its inputs and
outputs are modified

14. Block Diagram: Fault-tolerant control system using
signal correction

15. Fault tolerant control using Active & Passive LPV
method
• To comply with parameter-varying nature of the wind turbine along
its nominal operating trajectory, Linear parameter Varying(LPV) is
used.

16. Future scope
• More research is needed to develop an integrated FDI and FTC
system for online and real time operations.
• Design of active fault-tolerant controllers with reliable fault
diagnosis schemes.
• Qualitative model based fault detection might be used for providing
more information to the diagnostic system schemes.