Open Access

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.