Relevanz von Schieflasten in Niederspannungsnetzen im Kontext zunehmender Elektromobilität

To reduce the emissions of climate active gases, the federal german government decided in it’s „Klimaschutzplan 2050“ to restructure many sectors of public life [1]. This is also true for the personal transport sector. This way, a rejection of combustion engines should happen in favor of BEV, or battery electric vehicles. According to estimates, around three of four cars in cars in Germany should be BEV until 2050 [2]. These can use electricity from renewable sources instead of fossil fuels. To charge the batterys of these vehicles, there are wallboxes and charging stations in use even today. These are used decentralized on public parking lots, by employers or at home. It can be assumed, that the penetration of these BEV-chargers will increase with rising fleet share of BEV. This will prove a surplus load for the distribution grids. As many modells of BEV-chargers are connected to the grid with less than three phases, there will likely be more asymmetry in the grids. This work analyses, what level of asymmetry might occur until 2050 based on the assumed rise of BEV-penetration as well as what problems can arise for the management of the grids. Additionally, an estimate is done on the suitability of the often used symmetrical power flow analyses for dealing with the estimated levels of asymmetry.
To achieve this, three phased power flow simulations will be done on german distribution grids for a number of different estimates about the expression of BEV-penetration. Every simulation is repeated a statistical relevant number of times, each time changing the spatial allocation of BEV-chargers in a random pattern.Based on the extrema of voltage, line- and tranformer workload, the behaviour of the distribution grids is analysed for every estimated scenario. From that, the estimated level of asymmetry is derived.
The results of the investigation show, that most analysed grids are fit for the levels of asymmetry that happens in the more probable scenarios. The occuring asymmetry is distinctive for the use of many one-phased chargers and can reach 10 % and more. The symmetrical power flow analyses is unable to display the occuring level of asymmetry and should therefore be replaced by the asymmetrical power flow analysis, when many one-phased chargers are in use.