This paper proposes an efficient current control algorithm and a suitable power conversion system of a multiple-module transverse flux permanent magnet generator (MM-TFPMG) for large-scale direct-drive wind turbines. The MM-TFPMG is composed of multiple-module structures based on an independent three-phase configuration. In this paper, the single-phase current control applying the d-q transformation and the independent three-phase dqn-axes current control are proposed for the generator-side control of the MM-TFPMG. The control performance and characteristics of the single-phase dq-axes current control with a variable cutoff frequency and the independent three-phase dqn-axes current control using a concept of vector control are analyzed. As a result, the independent three-phase dqn-axes current control by using the vector control is an appropriate method to efficiently control the generator-side of the MM-TFPMG. The proposed algorithm is easily implemented and has less computation resource. Moreover, the control performance is better than the independent single-phase dq-axes current control despite the change of wind speed. The validity and usefulness of the proposed independent three-phase dqn-axes current control algorithm are verified and compared through several experimental results.@en

In order to maximize the energy harnessed, to minimize the cost, to improve the power quality and to ensure safety together with the growth of the size, various wind turbine concepts have been developed during last three decades. Different generator systems such as geared and direct-drive generator systems have been developed. Based on energy yield, reliability and maintenance problems, direct-drive generator systems have been regarded as a better concept than geared generator systems. Among different generator types, the permanent magnet synchronous generator (PMSG) is superior in overall efficiency. The PMSG has also been discussed as a concept with higher force density than the electrically excited (EE) generators. PMSG can thus be small and lightweight compared to induction generators and direct-drive electrically excited synchronous generators (EESG DD). Therefore, this thesis focuses on the research of the direct-drive permanent magnet synchronous generator system (PMSG DD) for large wind turbines. The main objective of this thesis is to find a design solution for large direct-drive wind generators with highest possible energy yield and lowest possible cost.@en

This paper presents a review of concepts for harvesting power from human movement and comparison of three axial flux permanent magnet machine (AFPM) designs. Some schemes for human power generating systems have been presented and compared in order to choose the most suitable configuration for our application. From the concepts evaluated, choices were made based on project specifications in the design of three axial flux permanent magnet (AFPM) machines with an output of 60W at a rotational speed of 3000 rpm. Comparison of the three AFPM generators: singled-sided with distributed winding, single-sided with concentrated windings, and double-sided (TORUS) with air gap winding show that the AFPM with concentrated windings and the TORUS are attractive having low mass and low losses.@en

This paper looks into a new concept for reducing the structural weight of large direct-drive generators used in wind turbines. The concept uses magnetic bearings to position the rotor of the generator. The use of magnetic bearings allows structural flexibility in the generator. The weight of the rotor using the new concept is compared to the weight of a rotor designed with conventional methods. For a 5-MW generator, the result is that the structural weight of the rotor reduces by 45%.@en

A direct drive generator used in wind turbine has high energy yield compared to other drivetrain topologies and low maintenance is expected as the technology matures. On the other hand direct drive generator weight and size increases rapidly when scaled up to larger units. This paper will investigate the possibility of weight reduction of large direct drive generator using magnetic bearings without compromising maintenance. Three different configurations using magnetic bearings i.e. single magnetic bearing concept, flexible rotor and hybrid concept have been analyzed. The results show that a combination of magnetic bearings and mechanical bearing with stiff radial structure and axial flexibility i.e. hybrid concept has the possibility to reduce weight of direct drive machine significantly compared to conventional design.@en

The aim of this paper is to review direct-drive generators and to suggest promising direct-drive generator concepts for large wind turbines. Different large direct-drive generators are compared based on the mass and the torque. Features of different PM machines are investigated to find promising machine type for direct-drive. The requirements and alternative solutions are suggested for both electromagnetic and mechanical design.@en

The aim of this paper is to design a lightweight transverse flux permanent magnet (TFPM) machine for large scale direct-drive wind turbines. The requirements for suitable generator systems for wind turbines are discussed. Analytical modeling of TFPM machines is discussed by considering the machine parameters and the magnetic circuit. The proposed analytical model is verified by comparing it to results of finite element analysis and experiments. A new lightweight TFPM machine is designed for a 10 MW direct-drive wind turbine and it is compared to the RFPM machine. Index Terms¿Direct-drive, most suitable generator, radial flux, transverse flux permanent magnet machine.@en