Optimiertes Lademanagement von E-Kfz zur Spannungsstabilisierung im Niederspannungsnetz

Abstract

In the context of climate-friendly energy generation and the reduction of the share of fossil fuels in the sectors of electricity, heat and transport, the integration of renewable energies continues. As a result of the long-term increase in energy prices, there is also a growing desire on the part of private individuals for energy independence as well as self-sufficiency with energy. This leads to a strong increase in single-phase and three-phase connected PV systems and battery storage systems as well as three-phase connected heat pumps, which in turn leads to new conditions due to the much higher rated power of the facilities. The transformation of the transportation sector and the push for electric mobility with 1,000,000 vehicles registered during 2021 will lead to a further increase in single-phase and three-phase loads. Low-voltage grids, in contrast to other grid levels, have the peculiarity that loads are largely connected in single-phase, as the operating equipment often has low loads. The much higher rated powers of PV systems, battery storage, heat pumps and electric vehicles have a direct impact on grid stability and are reflected by low and unbalanced grid voltages on the phases. This work deals with the balancing as well as the voltage stability of the three phases in the low-voltage grid using intelligent "Grid-to-Vehicle" (G2V) as well as "Vehicle-to- Grid" (V2G) applications of electric vehicles. Initially, the definition of unbalance and limit values as well as the calculation of unbalanced load flows is conducted. It is ana- lyzed how loads with both single-phase and three-phase grid connection generate unbalances. This is followed by the development of a G2V approach to balancing and a V2G approach to balancing and voltage stability. Based on existing measured values, given by the charging infrastructure, an optimization approach is applied to determine an optimal charging or discharging power to stabilize the grid state. Conceptually, no communication technology connection or stored network topologies in the electric vehicle are assumed. Within the framework of simulations for the defined scenarios 2020, 2025 as well as 2030, the function of the developed solution is demonstrated and the approaches without adaptation of the charging power are compared with G2V and V2G. The fundamental verification of the developed G2V approach is carried out within the framework of a hardware test. In a laboratory test, the G2V approach is implemented in an e-vehicle and the compensation of voltage unbalance is evaluated.