Comparison of a Modular Multilevel Converter – Virtual Synchronous Machine to a Synchronous Generator of the same power class in different grid scenarios

Abstract

The further domination of converter-based generation in power systems comes along with the loss of conventional power plants. Today, most of the converters use a current based control. However, due to the loss of inertia, this creates problems in network stability with an increasing number of converters in the power systems. This problem can be solved with converters, which adapt the behavior of a voltage source. The converters are operating in grid-forming mode. The Modular Multilevel Converter (MMC) provides many advantages over conventional converters, such as a high voltage quality and the elimination of filters on the ac-side. The future goal is a grid-forming MMC with a high robustness and stability. This paper provides an introduction to the controlling concept Virtual Synchronous Machine (VSM). It then compares the results of an implemented VSM controlled MMC to a synchronous generator in variational grid scenarios.