Publikationen

The Modular Multilevel Converter (MMC) is a proven topology in HVDC, but it is also a suitable solution for medium voltage applications such as wind turbines. To increase the modularity and the scalability of this topology for medium voltage applications, a real-time communication bus between the submodules and the central control unit is implemented as an efficient way of control. This real-time communication is realized using EtherCAT communication. To verify the advantages of this control strategy a 3-kV 350-kVA demonstrator of a medium voltage MMC topology with EtherCAT communication is constructed and set up. The description and the analysis of this demonstrator with focus on the EtherCAT communication are presented in this paper. The communication path, the synchronization and the control including the modulation method are discussed, investigated and validated within this paper.

The Resonant Commutated Twin Pole Inverter (RCTPI), a novel resonant pole inverter topology using only main switches, is introduced. One phase of a voltage source RCTPI consists of four switches arranged in two symmetric half-bridges called the twin poles. Each pole carries half of the phase current. The switches are turned off as zero voltage switch (ZVS) and zero current switch (ZCS) respectively and turned on under ZCS both. Switching losses in the semiconductor devices can be reduced in all operating points by soft switching, while overall losses are reduced only at high load currents. The concept can be realised using IGBTs in standard packages. Single switch modules, half- and full-bridge modules and some six-packs are suitable – this is an advantage compared to many other resonant topologies.

To reduce the losses of power inverters, resonant topologies replace hard switching power inverters. This paper shows the first investigations and measurements carried out to design a three phase current link power inverter in ARCP (Auxiliary Resonant Commutated Pole) topology as well as the finally measurements and results achieved with the complete system.