Potential of solid-state transformers for grid optimization in existing low-voltage grid environments

The transformation of the electrical energy system in Switzerland leads to a significant increase of decentralized, fluctuating generation sites connected to low-voltage (LV) grids. Voltage level restrictions have been identified as the main factor limiting the amount of photovoltaic generation systems which can be integrated in typical distribution grids. This work analyzes the future potential of solid-state transformers replacing conventional low-frequency transformers on level 6 of the electrical grid. Distribution grids are capital intensive and typically feature lifetimes of several decades. The analysis presented here, therefore, is based on the precondition of a persistent grid core. Two existing suburban grids in Switzerland have been investigated using DIgSilent Power Factory for grid simulations. The grid topologies are real and the load characteristics are based on long-term measurements. The focus of this work lies on the LV grid. SST capability to guarantee the required voltage quality is compared to alternative strategies or technologies, such as reactive power contribution by PV systems and distributed battery storage plants.