0000000000368997
AUTHOR
Peter Kepplinger
Optimal power tracking for autonomous demand side management of electric vehicles
Increasing electric vehicle penetration leads to undesirable peaks in power if no proper coordination in charging is implemented. We tested the feasibility of electric vehicles acting as flexible demands responding to power signals to minimize the system peaks. The proposed hierarchical autonomous demand side management algorithm is formulated as an optimal power tracking problem. The distribution grid operator determines a power signal for filling the valleys in the non-electric vehicle load profile using the electric vehicle demand flexibility and sends it to all electric vehicle controllers. After receiving the control signal, each electric vehicle controller re-scales it to the expected…
Decentralized price-driven grid balancing via repurposed electric vehicle batteries
Abstract The share of electricity generated from intermittent renewable sources, e.g., wind and solar grows rapidly. This affects grid stability and power quality. If the share of renewable power generation is to be increased further, additional flexibilities must be introduced. Aggregating small, distributed loads and energy storage facilities is a good medium-term option. In this paper, the suitability of decentralized and on-site optimized storage system consisting of repurposed electric vehicle batteries for grid balancing is investigated. Battery operation is controlled via an optimization procedure, which relies on a one-way communicated pseudo-cost function (PCF). Day-ahead electrici…
Decentralized on-site optimization of a battery storage system using one-way communication
Intermittent renewable energy sources (e.g. wind, solar energy systems) have been providing an exponentially growing share of electricity generation. Due to their highly transient and stochastic nature, they pose substantial challenges for power grid operation. Power dispatched from these sources are uncontrolled and do not necessarily coincide with demand; this in turn affects power quality. Hence, extensive demand side management (DSM) is required. DSM relies on flexible loads as well as energy storage facilities. Furthermore, renewable power generation is by its very nature highly distributed and consists of large numbers of small units. These have a substantial effect on traditional pow…
Voltage-Based Droop Control of Electric Vehicles in Distribution Grids under Different Charging Power Levels
If left uncontrolled, electric vehicle charging poses severe challenges to distribution grid operation. Resulting issues are expected to be mitigated by charging control. In particular, voltage-based charging control, by relying only on the local measurements of voltage at the point of connection, provides an autonomous communication-free solution. The controller, attached to the charging equipment, compares the measured voltage to a reference voltage and adapts the charging power using a droop control characteristic. We present a systematic study of the voltage-based droop control method for electric vehicles to establish the usability of the method for all the currently available resident…
Violation-mitigation-based method for PV hosting capacity quantification in low voltage grids
Hosting capacity knowledge is of great importance for distribution utilities to assess the amount of PV capacity possible to accommodate without troubling the operation of the grid. In this paper, a novel method to quantify the hosting capacity of low voltage grids is presented. The method starts considering a state of fully exploited building rooftop solar potential. A downward process is proposed—from the starting state with expected violations on the grid operation to a state with no violations. In this process, the installed PV capacity is progressively reduced. The reductions are made sequentially and selectively aiming to mitigate specific violations: nodes overvoltage, lines overcurr…
Field testing of repurposed electric vehicle batteries for price-driven grid balancing
Abstract As electric cars become more widespread, the disposal and recycling of used batteries will become an important challenge. Typically, vehicle batteries are replaced if their capacity drops to 70–80% of initial capacity. However, they may still be useful for stationary applications. In this paper, results from a field test of a molten salt high-temperature electric vehicle battery repurposed as stationary storage for grid balancing are presented. In a previous study, we have shown that a mixed integer linear programming control strategy driven by a spot-market price for electricity is best suited for an implementation on hardware with limited computational resources. A 14-day experim…
Autonomous Demand Side Management of Electric Vehicles in a Distribution Grid
The electricity demand due to the increasing number of EVs presents new challenges for the operation of the electricity network, especially for the distribution grids. The existing grid infrastructure may not be sufficient to meet the new demands imposed by the integration of EVs. Thus, EV charging may possibly lead to reliability and stability issues, especially during the peak demand periods. Demand side management (DSM) is a potential and promising approach for mitigation of the resulting impacts. In this work, we developed an autonomous DSM strategy for optimal charging of EVs to minimize the charging cost and we conducted a simulation study to evaluate the impacts to the grid operation…