Dynamic behaviour of grid forming inverters when providing static voltage support via Q(V) characteristics

For effective parallel operation with existing systems, it makes sense for grid-connected systems to fulfil the requirements placed on converters in accordance with VDE-AR-N 4105 as precisely as possible. This also includes static voltage support, which makes it possible to counteract the voltage increase caused by feed-in and to significantly increase the absorption capacity of distribution grids for decentralised energy systems. This motivates the investigations published here in the “Fuchstal-leuchtet” and “Verteilnetz 2030+” projects as to whether grid-forming systems are also capable of implementing the static voltage support methods in accordance with VDE-AR-N 4105. This is a major challenge, particularly due to the fact that grid-forming systems directly influence the voltage. In a previous work, the ability of a grid-forming inverter to realise a Q(V) characteristic curve in a laboratory environment in parallel operation with a grid-following inverter has already been demonstrated. In this work, the dynamic interactions of the two inverters are considered. This includes different start-up time constants of the Q(V) control and varying positions of the inverters in the grid. In addition, the reaction to rapid voltage changes is analysed.