Voltage-Dependent Load-Leveling Approach by Means of Electric Vehicle Fast Charging Stations

Abstract

Intermittent generation and load demand are one of the major challenges for grid operators. Caused for example by renewables power variability or electric vehicle charging, it can create mismatches between the real-time demand and the forecast demand, affecting frequency regulation. To alleviate this mismatch, operators have to resort either on the balancing market or on extensive use of energy storage systems, which increases operation costs. This article introduces a load-leveling approach exploiting the voltage dependence of the loads. With a controlled reactive power injection, the converters of fast charging stations can influence the voltage profile and, consequently, the power consumption of voltage-dependent loads. The approach has two main goals: minimizing the mismatches with respect to the demand forecast and reducing the grid losses. Fast charging stations are particularly suited for this approach. Being employed with full capacity for charging only for short time, their spare capacity can be exploited to apply the load-leveling approach. This proposed approach is discussed theoretically and analyzed in a modified distribution network in Northern Germany. Parameters variation analysis has been performed to thoroughly demonstrate the effectiveness of the approach under different load/grid conditions. Its feasibility has been evaluated by means of power-hardware-in-the-loop tests.