The objective of this paper is to compare five different generator systems for wind turbines, namely the doubly-fed induction generator with three-stage gearbox (DFIG3G), the direct-drive synchronous generator with electrical excitation (DDSG), the direct-drive permanent-megnet generator (DDPMG), the permanent-magnet generator with single stage gearbox (PMG1G), and the doubly-fed induction generator with single-stage gearbox (DFIG1G). The comparison is based on cost and annual energy yield for a given wind climate. The DFIG3G is a cheap solution using standard components. The DFIG1G seems the most attractive in terms of energy yield divided by cost. The DDPMG has the highest energy yield, but although it is cheaper than the DDSG, it is more expensive than the generator systems with gearbox

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Comparison of direct-drive and geared generator concepts for wind turbines

With rapid development of wind power technologies and significant growth of wind power capacity installed worldwide, various wind turbine concepts have been developed. The wind energy conversion system is demanded to be more cost-competitive, so that comparisons of different wind generator systems are necessary. An overview of different wind generator systems and their comparisons are presented. First, the contemporary wind turbines are classified with respect to both their control features and drive train types, and their strengths and weaknesses are described. The promising permanent magnet generator types are also investigated. Then, the quantitative comparison and market penetration of different wind generator systems are presented. Finally, the developing trends of wind generator systems and appropriate comparison criteria are discussed. It is shown that variable speed concepts with power electronics will continue to dominate and be very promising technologies for large wind farms. The future success of different wind turbine concepts may strongly depend on their ability of complying with both market expectations and the requirements of grid utility companies.

Overview of different wind generator systems and their comparisons

Every year the number of installed wind power plants in the world increases. The horizontal axis wind turbine is the most common type of turbine but there exist other types. Here, three different wind turbines are considered; the horizontal axis wind turbine and two different concepts of vertical axis wind turbines; the Darrieus turbine and the H-rotor. This paper aims at making a comparative study of these three different wind turbines from the most important aspects including structural dynamics, control systems, maintenance, manufacturing and electrical equipment. A case study is presented where three different turbines are compared to each other. Furthermore, a study of blade areas for different turbines is presented. The vertical axis wind turbine appears to be advantageous to the horizontal axis wind turbine in several aspects.

Evaluation of different turbine concepts for wind power

Accurate prediction of range of an electric vehicle (EV) is a significant issue and a key market qualifier. EV range forecasting can be made practicable through the application of advanced modelling and estimation techniques. Battery modelling and state-of-charge estimation methods play a vital role in this area. In addition, battery modelling is essential for safe charging/discharging and optimal usage of batteries. Much existing work has been carried out on incumbent Lithium-ion (Li-ion) technologies, but these are reaching their theoretical limits and modern research is also exploring promising next-generation technologies such as Lithium–Sulphur (Li–S). This study reviews and discusses various battery modelling approaches including mathematical models, electrochemical models and electrical equivalent circuit models. After a general survey, the study explores the specific application of battery models in EV battery management systems, where models may have low fidelity to be fast enough to run in real-time applications. Two main categories are considered: reduced-order electrochemical models and equivalent circuit models. The particular challenges associated with Li–S batteries are explored, and it is concluded that the state-of-the-art in battery modelling is not sufficient for this chemistry, and new modelling approaches are needed.

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A review on electric vehicle battery modelling: From Lithium-ion toward Lithium–Sulphur

This paper reviews the trends in wind turbine generator systems. After discussing some important requirements and basic relations, it describes the currently used systems: the constant speed system with squirrel-cage induction generator, and the three variable speed systems with doubly fed induction generator (DFIG), with gearbox and fully rated converter, and direct drive (DD). Then, possible future generator systems are reviewed. Hydraulic transmissions are significantly lighter than gearboxes and enable continuously variable transmission, but their efficiency is lower. A brushless DFIG is a medium speed generator without brushes and with improved low-voltage ride-through characteristics compared with the DFIG. Magnetic pseudo DDs are smaller and lighter than DD generators, but need a sufficiently low and stable magnet price to be successful. In addition, superconducting generators can be smaller and lighter than normal DD generators, but both cost and reliability need experimental demonstration. In power electronics, there is a trend toward reliable modular multilevel topologies.

Trends in Wind Turbine Generator Systems

The thesis deals with the issue of cost reduction in direct-drive generators for wind turbines. Today, the combination gearbox-medium-speed (1000-2000 rpm) induction generator largely dominates the market of MW-scale wind turbines. This is due to the lower costs of the gearbox option compared to the costs of gearless systems. Nevertheless, there is an acute interest among researchers and wind turbine suppliers in the possibility of removing gears and slip rings from the drive train, leading to lower maintenance (no oil is required and slip rings can be avoided) and higher reliability due to the absence of wear between gears. The direction followed by the thesis is the investigation and comparison of various permanent magnet (PM) machine topologies. The aim is to identify the topology(ies) with the lowest cost/torque and highest torque/ mass. A new TFPM geometry, called TFPM machine with toothed rotor, is derived in the. The new machine topology has the following characteristics: the stator is single-sided, the rotor PM and flux concentrators are independent from the build-up of mechanical tolerances, the installation of rotor parts (PM and flux concentrators) can be automated and the flux circulation allows laminated steel to be used in the stator core. A prototype of the TFPM machine with toothed rotor is presented. The comparison between TFPM machines with toothed rotor and conventional PM synchronous machines is discussed. Comparison of the cost/torque and torque/mass of the two machine topologies for diameters ranging between 0.5 m and 3.0 m showed favorable expected performances of the TFPM machine with toothed rotor for diameters of 0.5 m and 1.0 m. However, diameters larger than 1.0 m favored the conventional PM synchronous machine with/without flux-concentration. Using the results of the optimization process, the costs of active material are computed for a 1.5 MW wind turbine. It is found that active material represents about 5% of the total turbine cost, while previous estimates indicated that the generator costs are rather between 30% and 40% of a complete direct-drive wind turbine. Therefore, further optimizaÂ¬tion of direct-drive machines should also include the costs of manufacturing and the costs of the mechanical structure.

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Optimized Permanent Magnet Generator Topologies for Direct-Drive Wind Turbines

This paper gives an overview of electrical conversion systems for wind turbines. First, the basics of wind energy conversion with wind turbines are reviewed and requirements with respect to the electric system are considered. Next, the three classical conversion systems are described with their strengths and weaknesses: constant speed, variable speed with doubly-fed induction generator and variable speed with direct-drive generator. The applied power electronic converters are shortly addressed. Finally alternative generator systems and trends are discussed. There is a clear trend towards variable speed systems. Doubly-fed induction generator systems are increasingly equipped with grid fault ride through capabilities. For direct-drive turbines, the radial flux permanent-magnet synchronous generator is cheaper and more efficient than the electrically excited synchronous generator. It is expected that the voltage level of generators will increase up to values in the order of 5 kV.

Basic Operation Principles and Electrical Conversion Systems of Wind Turbines

In direct-drive wind turbines, the generator outer diameter and cost must be reduced substantially to allow a higher penetration of direct-drive wind-turbines on the market. In this paper, different generator topologies are investigated. A comparison is carried out, on the basis of 60 different machine prototypes built or designed by numerous authors. Data for those machines is found in the scientific literature. The comparison is based on torque density and cost/torque. Only the machines active material is considered. (au)

Comparison of generator topologies for direct-drive wind turbines

The performance of a dual energy storage electric vehicle system mainly depends on the quality of its power and energy managements. A real-time management strategy supported by a model predictive control (MPC) using the nonuniform sampling time concept is developed and fully addressed in this paper. First, the overall multiple energy storage powertrain model including its inner control layer is represented with the energetic macroscopic representation and used to introduce the energy strategy level. The model of the system with its inner control layer is translated into the state-space domain in order to develop an MPC approach. The management algorithm based on mixed short- and long-term predictions is compared to rule-based and constant sampling time MPC strategies in order to assess its performance and its ability to be used in a real vehicle. The real-time simulation results indicate that, compared to other strategies, the proposed MPC strategy can balance the power and the energy of the dual energy storage system more effectively, and reduce the stress on batteries. Moreover, battery and supercapacitor key variables are kept within safety limits, increasing the lifetime of the overall system.

Adaptive Energy Management System Based on a Real-Time Model Predictive Control With Nonuniform Sampling Time for Multiple Energy Storage Electric Vehicle

Specific applications such as recreational vehicles require new developments with respect to their energy storage system (ESS). Despite some recent trends in battery development, the ratio between power and energy has not yet met the requirements of these specific kinds of vehicles. This paper presents the integration of a SuperCapacitors (SCs) pack in a three-wheel electric vehicle considering the energy- and power-split management strategy. An energy-management strategy based on a comprehensive fuzzy logic controller approach is fully addressed to increase the global efficiency and performance of the studied vehicle. The proposed control and management strategy ensures that the battery supplies the average portion of the power demand, while the energy level of the SCs is smartly handled. The proposed strategy is easily adaptable to other vehicles or different driving modes. The approach was validated with a power-level hardware-in-the-loop (HIL) platform for a reduced-scale hybrid dual ESS. This experimental test allows real-time verification of the proposed energy management and evaluates the ability to coordinate more efficiently the energy flow. The proposed approach enhances the battery lifetime by reducing the battery current root-mean-square (RMS) value by 12% compared to a battery-only architecture.

Maxime R. Dubois

Papers

Optimized Permanent Magnet Generator Topologies for Direct-Drive Wind Turbines

Basic Operation Principles and Electrical Conversion Systems of Wind Turbines

Comparison of generator topologies for direct-drive wind turbines

Adaptive Energy Management System Based on a Real-Time Model Predictive Control With Nonuniform Sampling Time for Multiple Energy Storage Electric Vehicle

Energy- and Power-Split Management of Dual Energy Storage System for a Three-Wheel Electric Vehicle