Back to the programme printer.gif Print



Wednesday, 12 March 2014
09:00 - 10:30 Advanced electrical systems: From megabyte to megawatt
Hardware Technology  


Room: Tramuntana
Session description

The electrical system is the most powerful and also the most sensitive system in a turbine, with small sensor faults often causing fault errors. It is also the most critical system, responsible for control of the machine, power shaping and power delivery. The session will show how electrical systems can be optimised in turbines, how they can be made more secure and robust, as well as looking at future trends for electrical systems.

Learning objectives

  • Get inside knowledge of future trends and technologies in electrical systems, including; generator, converter, control and communication systems
  • Learn about the interaction of electrical systems to turbine loads as well as mechanical systems and the grid
  • Discover and understand trends in grid connection requirements and their impact on electrical design
Lead Session Chair:
Björn Andresen, Siemens Wind Power, Denmark
Tobias Rösmann Moog, Germany
Co-authors:
Tobias Rösmann (1) F P Steffen Adelt (1)
(1) Moog, Unna, Germany

Printer friendly version: printer.gif Print

Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Dr.-Ing. Tobias Rösmann got his diploma in electrical engineering in 2006 from the TU Dortmund/Germany and then started with Moog as development engineer for Pitch Systems. In 2012 he obtained his Ph.D. degree in the field of electrical drive and motor control from the University of Wuppertal. Since then he's been leading the Department for Wind Technology Development at Moog.

Abstract

SELF-SENSING CLOSED-LOOP PITCH-SPEED CONTROL REDUCING WIND TURBINE STRUCTURAL LOADS DURING TURBINE EMERGENCY STOP

Introduction

The Wind Turbine Pitch Control System has to fulfill two essential functions:
It’s one of the actuators for the turbine speed and power control when the wind speed exceeds the turbine rated values.
Secondly the system is the actuator for the wind turbine braking system. In order to stop the turbine, all three blades have to be moved into the feathering position.
In order to distribute and balance the turbine loads for all structural parts during the turbine-stop-procedure , all three pitch axis have to move out of the wind synchronously.

Approach

Different open loop control schemes exist as state of the art for the pitch actuator feathering drive if the pitch axis position feedback signal is lost: Hydraulic Actuators are operated directly by the hydraulic pressure storage by passing the servo valve, DC Motor Pitch Actuators are directly connected to the electrical DC backup source and AC induction Pitch Actuators are controlled via open loop V/F control in case of a broken axis feedback signal.
These open loop control schemes have one common disadvantage: The speed of each individual axis highly depends on the load applied by the blade.

Main body of abstract

The impact of the pitch position incoherence on the turbine loads has been analyzed with the GH bladed.
As a conclusion, a new self-sensing model based closed loop speed control scheme has been implemented in the Pitch Axis Servo Controllers. With this new control feature in place, a synchronous movement out of the wind of all three blades can be achieved even in case of position feedback fault(s) in the pitch axis.
This paper presents the results of the GH Bladed based case study to demonstrate the influence of pitch position incoherence on the turbine structural loads during the feathering run.
An innovative solution, a self-sensing closed loop speed control scheme for specially designed Interior Permanent Magnet Synchronous Motor (IPMSM), is presented. Compared to state of the art V/F-control schemes, this self-sensing control scheme provides up to 3 times rated torque from standstill in order to ensure a safe and high performance movement into the feathering position.
Also the standardized performance qualification process for the pitch actuators with and without position sensor is described which ensures a robust and reliable performance of the pitch actuators in the field.
In the last part of the paper measurement results from the dynamic load test bench will be presented. The torque-speed performance during feathering run of the new self-sensing control scheme is compared with state of the art DC motor and V/F-controlled AC-induction motor open loop control scheme.



Conclusion

In this paper the influence of pitch position incoherence is analyzed with the turbine design tool GH bladed. The results highlight the importance of a synchronized movement of the blades during the feathering drive.
A new control scheme is presented to achieve a synchronous movement of all three blades even in case of position feedback fault(s) in the pitch axis. An approach to standardize the performance qualification testing of the pitch actuators is presented. Finally measurement results show the advantages of the developed self-sensing closed-loop control by a comparison with state of the art open-loop control schemes.



Learning objectives
This paper shows the significance of synchronized pitch positions during the turbine stop-procedure. It also explains the principles of self-sensing closed loop control for interior permanent magnet machines and concludes on the benefits for the overall turbine. In addition a performance qualification process for pitch actuators is introduced to ensure a safe and reliable pitch actuator performance especially during the feathering operation duty cycle.