Ultra-High-Bandwidth Power Amplifiers: A Technology Overview and Future Prospects
Julian Bohler, Jonas Huber, Johann Wurz, Martin Stransky, Nissim Uvaidov, Srdjan Srdic, Johann W. Kolar
Abstract
Testing of power electronic converters can advantageously be carried out in power-hardware-in-the-loop (P-HIL) environments that emulate the behavior of power grids, electric motors, etc. The interface between the model and the device under test requires a power amplifier whose bandwidth ultimately limits the accuracy of the emulation. Hence, there is a need for general-purpose AC power amplifiers with ultra-high power bandwidth. This paper first provides a comprehensive review of amplifier concepts proposed over the past decades, i.e., linear power amplifiers, switch-mode amplifiers, including advanced variants such as multilevel (parallel-interleaving) and multicell (series-interleaving) topologies, as well as hybrid approaches that, e.g., combine analog and switch-mode stages. Based on this review, the two key concepts (parallel-interleaving of bridge-legs and cascading of converter cells) that facilitate high efficiency and ultra-high power bandwidth are identified and discussed, covering also suitable isolated mains interfaces and control considerations. Finally, we present a three-phase amplifier system that uses six cascaded converter cells per phase to realize an effective switching frequency of 3.6 MHz. The prototype thus achieves a measured power bandwidth of 100 kHz at the nominal phase output voltage of 230Vrms, and an output power of up to 10 kW per phase.