Controller Optimization for 6MW 2 Bladed Offshore Wind Turbine

◀ Back to projects overview P201101-002-2BE

2-B Energy will build an algorithm to be able to quickly and efficiently test algorithms for their turbine control system.

Project summary

2-B Energy is developing a dedicated offshore wind turbine based on: a full jacket support structure concept with integrated design of tower and foundation; suitable for large distance from the coast with helicopter access; sophisticated control system to reduce dynamic and extreme loads; and optimized for high availability by efficient service & maintenance & repair. The turbine is categorized as a 6MW, 2 blade horizontal axis wind turbine. The turbine is referred to as 2B6.

Main objective of the project
The main objective of the project was to reduce Cost of Energy by optimization of control design tools which enable 2-B Energy to define a dedicated turbine control system suitable for 2 bladed 6MW offshore wind turbine. With these control design tools, 2-B Energy should be able to enhance the performance of the control system by taking an integrated design approach for the design of the control system in close cooperation with the design of the wind turbine itself, and support structure. The control optimization has resulted in reduction of loads on the 2 bladed 6MW offshore wind turbine and the full truss support structure.

The approach and the results obtained
The approach taken was to develop a Low Order Degree Of Freedom Model (LODOFM) of the 2B6 turbine and the support structure in Matlab. This model has been verified with data results obtained by Garrad Hassan’s Bladed; Bladed is the industry standard integrated software package used for the design and certification of onshore and offshore turbines. With this LODOFM a basic control system was designed which includes control options such as collective pitch control used for rotor speed and power control; damping in the fore-aft and side-side direction and damping upon the drive train. Other principles such as Individual Pitch Control (IPC) which reduces the asymmetric loading upon the turbine were implemented and a supervisory control system which detects whether control limits have been exceeded and activates stopping procedures in case of exceedance.

The second phase was the conversion of the Matlab code to C++ code such that the control system can be connected to Bladed by means of dynamic-link library (DLL). At the end of the second phase, the source code of a simulation controller was available.

The integrated design approach enabled 2-B Energy to improve the control behaviour of the turbine with significant reductions with respect to loading upon the wind turbine. An overall reduction of 7 % has been achieved compared to the wind turbine loading at the beginning of this project. These reductions in loading enhance reduction of mass of individual components, and thereby reduce the material costs. All these improvements lead to a reduction in Cost of Energy.

A second part of cost reduction is in-house capability to develop, modify and optimize the control system and therefore not depend upon expensive consultants.

Risk reduction of Far-offshore wind energy is achieved by reduced loading upon the individual components, thereby increasing the reliability of the components and reducing the risk of unplanned maintenance.

Contribution of the project results to cost and risk reduction for Far-offshore wind energy
The estimated reduction in CAPEX and OPEX; and the increase in Annual Energy Production (AEP) for this project are quantified as:

CAPEX: Turbine and support structure mass reduction of 1.3%

OPEX: Operations and Maintenance cost reduction of 3%

AEP: Availability increase of 1%

The Cost of Energy reduction was quantified by using the FLOW Cost Model which results in a reduction of CoE of 2.1% compared to the CoE at the beginning of the FLOW project. Although the comparison made here is between two 2-B Energy concepts/designs the results achieved could also be applicable in a broader sense as improvement are mainly related to controller optimizations.

During the project the significant load reductions inspired 2-B Energy to further optimize the 2B6 turbine for further reduction in the Cost of Energy. These optimizations are done in two parallel paths in successive FLOW projects regarding:

“Advanced Controller Optimization for 6MW 2 Bladed Offshore Wind Turbine”, The Key focus points are optimizing and supplementing the basic wind turbine control system with advanced control strategies. The control optimization will result in reduction of loads.
“Upgrade to 140 meter rotor diameter on a two-bladed downwind turbine”, FLOW Project P201204-001-2BE. The key focus points are enlarging the rotor diameter from 130m to 140m by application of Individual Pitch Control and generating design documents for the 2B6 beta turbine in 2012 which can be submitted to the certifying body for certification.

Detailed information of both projects can be found in the respected project proposals and final reports. With the introduction of a dedicated offshore wind turbine with improved cost of energy, 2-B Energy aims to a significant cost and risk reduction of far and large offshore wind energy.