Dual-rotor Wind Turbines Research Articles

A Novel Dual-Rotor Turbine for Increased Wind Energy Capture

Horizontal axis wind turbines suffer from aerodynamic inefficiencies in the blade root region (near the hub) due to several non-aerodynamic constraints. Aerodynamic interactions between turbines in a wind farm also lead to significant loss of wind farm efficiency. A new dual-rotor wind turbine (DRWT) concept is proposed that aims at mitigating these two losses. A DRWT is designed that uses an existing turbine rotor for the main rotor, while the secondary rotor is designed using a high lift-to-drag ratio airfoil. Reynolds Averaged Navier- Stokes computational fluid dynamics simulations are used to optimize the design. Large eddy simulations confirm the increase energy capture potential of the DRWT. Wake comparisons however do not show enhanced entrainment of axial momentum.

A study on the design of a new power transmission for wind turbines

The single-rotor wind turbine remains the dominant design for energy production. However, this design requires improvements to overcome some of its limitations. The introduction of the dual rotor system regarded as improvement over the single-rotor system in Korea due to its high efficiency, despite Korea’s low wind quality. Many researchers have attempted to devise different dual rotor machines and assess their power production capabilities under similar wind conditions to those in Korea. Existing power transmissions for dual-rotor wind turbines have issues with the complexity of design, difficulty in manufacturing, high costs and low efficiencies. Therefore, the aim of this study was to design a new power transmission for the dual-rotor wind turbine with an alternative to the bevel-planetary system by using a planetary system. This new method is dependent on the torque ratio and not the gear ratio as in common gear systems. The design and analysis of each part, such as the gears, shafts, bearings and control mechanisms are included in this study. The design is based on the power transmission of a motor vehicle. A prototype of the design is manufactured to verify the proposed method. The experimental results show that the new planetary-type gear box incurs fewer energy losses, has a high efficiency and low manufacturing costs. It is anticipated that the proposed design might be suitable for use with commercial wind turbines.

Comparison of fault-ride-through capability of dual and single-rotor wind turbines

The majority of wind turbines currently in operation have the conventional concept design. That is a single-rotor wind turbine (SRWT) which is connected through spur gearbox to a generator. Recently, dual-rotor wind turbine (DRWT) has been introduced to the market. It has been proven that the steady state performance of the DRWT system for extracting energy is better than the SRWT. But, a comparison of fault-ride-through capability of these two types of turbines requires further research. In this paper, the fault-ride-through capability of DRWT and SRWT are evaluated and compared when generating units are operating at constant pitch angle and constant speed modes. Constant pitch angle mode is simulated to investigate the natural damping of DRWT and SRWT. To verify the time domain simulation results, damping characteristics of DRWT and SRWT are also compared through eigenvalue analysis and speed droop characteristics of the control system. The accuracy of the aerodynamic model of the DRWT is enhanced by including the stream tube effect in the simulation. It was uncovered that DRWT introduces higher damping torque to the network in both constant speed and constant pitch angle modes. This advantage improves the transient performance of DRWT-based wind farms. ► Dynamics of dual-rotor wind turbine (DRWT) and single-rotor wind turbine (SRWT) are studied. ► Fault-ride-through capability of DRWT and SRWT are evaluated and compared. ► Damping characteristics of DRWT and SRWT are compared through eigenvalue analysis. ► Accuracy of the aerodynamic model of DRWT is enhanced by including the stream tube effect. ► DRWT introduces higher damping torque in both constant speed and constant pitch angle modes.

공력해석 및 구조시험을 통한 소형 복합재 블레이드의 구조 안전성 평가

This paper deals with the aerodynamic analysis and structural test under estimated loading condition for small composite blade, which is utilized in dual rotor wind turbine system. Firstly, the front and rear blades of dual rotor wind turbine system were modeled using reverse engineering method. And using finite volume method, the aerodynamic forces were analyzed at the rated and cutout wind speed to identify the pressure distribution on blades. And then, the full scale structural tests were conducted according to load and strength based methodology in IEC 61400-2 to identify the structural integrity of composite blade.

Modeling, control, and simulation of dual rotor wind turbine generator system

A new wind turbine generator system (WTGS) is introduced, and its mathematical model, blade pitch control scheme, and nonlinear simulation software for the performance prediction are presented. The notable feature of WTGS is that it consists of two rotor systems positioned horizontally at upwind and downwind locations, and a generator installed vertically inside the tower. In this paper, this new WTGS is treated as a constrained multi-body system, and the equations of motion are obtained by using the multi-body dynamics approach. Aerodynamic forces and torques generated from each of rotor blades are calculated using the blade element theory. Various pitch control schemes depending on the wind speed and the main rotor's rotational speed are implemented. A relatively simple model for the load torque is obtained by using the test data of the doubly fed induction generator adopted in the new WTGS. Finally, FORTRAN and Matlab/Simulink-based hybrid simulation software is developed and used to predict and analyze the performance of the WTGS.

풍력발전시스템 성능 해석 S/W의 초기 검증에 관한 연구

본 논문에서는 풍력발전시스템의 정상 및 과도 응답과 같은 동적 거동 분석은 물론 피치제어 시스템의 성능 예측을 위하여 개발된 시뮬레이션 소프트웨어의 검증을 위하여 실제 현장에서 측정한 자료와 비교 검증을 수행하였고 실제와 유사하도록 시스템 모델링 및 소프트웨어의 개선 방향을 제시함으로써 향후 본 연구를 통하여 개발한 소프트웨어의 유용성을 제시하고자 한다. The simulation software for predicting the performance of a wind turbine generator system (WTGS) is validated using the field measured data obtained from the idling test run of a dual rotor wind turbine recently developed and installed in Korea. Both steady-state and transient responses at low and high wind conditions are compared with the theoretically predicted ones from the simulation software WINSIM.

Dual-Rotor 풍력 발전 시스템 성능 해석 및 피치 제어에 관한 연구

In this paper, preliminary results for performance prediction of a dual-rotor wind turbine generator system are presented. Blade element and momentum theories are used to model the aerodynamic forces and moments acting on the rotor blades, and multi-body dynamics approach is used to integrate the major components to represent the overall system. Not only the steady-state performance but the transient response characteristics are analyzed. Pitch control strategy to control the rotor speed and the generator output is proposed and its performance is verified through the nonlinear simulation.