This review article aims to provide an overview and insight into the most relevant aspects of wind energy development and current state-of-the-art. The industry is in a very mature stage, so it seems to be the right time to take stock of the relevant areas of wind energy use for power generation. For this review, the authors considered the essential aspects of the development of wind energy technology: research, modeling, and prediction of wind speed as an energy source, the technology development of the plants divided into the mechanical and electrical systems and the plant control, and finally the optimal plant operation including the maintenance strategies. The focus is on the development in Europe, with a partial focus on Germany. The authors are employees of the Fraunhofer Institutes, Institute for Energy Economics and Energy Systems Technology and Institute for Wind Energy Systems, who have contributed to the development of this technology for decades.

This paper deals with the optimization of the components of a multiphase interleaved operated buck converter for battery charging applications and proposes two control strategies. The proposed control strategies allow the number of active phases and the switching frequency to be adapted according to the output power, enabling a significant increase to the power handling capability without increasing the size of the power semiconductor. This can be further exploited to decrease the size of the semiconductor and the cooling system for a given power. In addition, the partial load efficiency of the converter is increased significantly. Finally an experimental validation is presented.

This paper shows a new concept to generate medium voltage (MV) in wind power application to avoid an additional transformer. Therefore, the generator must be redesigned with additional constraints and a new topology for the power rectifier system by using multiple low voltage (LV) power rectifiers connected in series and parallel to increase the DC output voltage. The combination of parallel and series connection of rectifiers is further introduced as DC-cascade. With the resulting DC-cascade, medium output voltage is achieved with low voltage rectifiers and without a bulky transformer. This approach to form a DC-cascade reduces the effort required to achieve medium DC voltage with a simple rectifier system. In this context, a suitable DC-cascade control was presented and verified with a laboratory test setup. A gearless synchronous generator, which is highly segmented so that each segment can be connected to its own power rectifier, is investigated. Due to the mixed AC and DC voltage given by the DC-cascade structure, it becomes more demanding to the design of the generator insulation, which influences the copper fill factor and the design of the cooling system. A design strategy for the overall generator design is carried out considering the new boundary conditions.

The recent transformation of the energy sector brings new challenges in areas such as supply security, efficiency and reliability. Especially the increase of decentralized power plants leads to a more complex energy system and an increasing complexity. This requires expansion and digitization of the power grid as well as an initiative-taking operation of the grid operator. To investigate such complex systems and its phenomena, modern development methods such as real-time simulation or digital twins (DT) can be used. In this approach a digital replica of the real-world system, a grid section, is developed, which can represent or predict the behavior of the real distribution grid. For this, a model of the real-world system is derived and implemented in a co-simulation environment, in which it receives data via an analyzer or measurement system from the grid model. This paper focuses on the development of the digital twin of a testing grid and a grid analyzer for the measurement. With the digital twin of the testing grid, a first approach is achieved in a real-time capable environment showing the functionalities and interactions of a digital twin. Subsequently the development of the digital twin model is explained, and the results are discussed

This paper proposes a novel control strategy for multiphase interleaved dc-dc converters for EV battery charging applications. The proposed control strategy allows to adapt the number of active phases and the switching frequency according to the output power. This strategy results to an increased partial load efficiency and current handling capability of the semiconductors while the size of the semiconductor, the magnetic components and the cooling system size is reduced. An experimental validation of the proposed method is presented.

This paper presents the design and control structure of a synchronous generator in ring form. The analysed generator is designed in order to test the control structure of a light-weight 10 MW generator for wind turbines. A segmented stator structure with distributed control allows control of the current of single stator segments which facilitates damping of axial displacement due to varying wind speeds by controlling axial forces. The layout process of the generator, its distributed control and the damping control are presented in this paper.