Using Multiple Stator Windings and Multi-Level Converters for Frequency Matching in Microturbine Generators

The microturbine generator is a useful power source in distributed generation applications, but usually requires a conversion stage, to match its frequency to that of the utility grid. In this work we propose using multiple stator windings for frequency matching in microturbine generators. This approach is based on the idea that the generator itself can be seen as a transformer, with multiple windings. Following this logic, we propose to redesign the microturbine stator windings as multiple transformers, replacing a single 3-phase output with multiple 3-phase outputs. Each output is rectified, and function as an individual isolated DC voltage source, which connects directly to a modular multilevel converter. The proposed method uses no additional magnetic components other than the ones that already exist on the modified stator. Therefore, it can significantly minimize the overall system's footprint. Additionally, this method uses a low switching frequency, as low as the utility grid's frequency, which allows using very simple switching devices, with low switching losses. Another unique feature of this method is that as the number of submodule stages is increased, the output filter is considerably simplified. The results are verified using simulations and experiments.