Detailed discrete-time implementation of a battery-supported synchronverter for weak grids

The emulation of synchronous machines is an attractive solution to improve the integration of distributed energy resources in weak grids. In this sense, synchronverters have been widely analysed in the literature, but their digital implementation has been seldom studied. This paper presents the discrete-time implementation of the control algorithms for a battery-supported synchronverter in a weak grid. First of all, the formulation is described in a synchronous reference frame and a simple method to adjust the parameters is described. Some modifications are proposed to the classical synchronverter that will be implemented in its incremental form. By using this implementation method the control system a) becomes easier to implement, b) wind-up problems are avoided, and c) command signals are easier to saturate. Since the control system is non-linear, these features are of a particular relevance. All the control developments are tested experimentally in a 15 kVA converter with a 47.5 kWh Li-ion battery connected to a weak grid.