Frederik Geth

Multiobjective Battery Storage to Improve PV Integration in Residential Distribution Grids

This paper investigates the potential of using battery energy storage systems in the public low-voltage distribution grid, to defer upgrades needed to increase the penetration of photovoltaics (PV). A multiobjective optimization method is proposed to visualize the trade-offs between three objective functions: voltage regulation, peak power reduction, and annual cost. The method is applied to a near-future scenario, based on a real residential feeder. The results provide insight into the dimensioning and the required specifications of the battery and the inverter. It is found that an inverter without batteries already achieves part of the objectives. Therefore, the added value of batteries to an inverter is discussed. Furthermore, a comparison between lithium-ion and lead-acid battery technologies is presented.

Electric Vehicle Charging in an Office Building Microgrid With Distributed Energy Resources

This paper discusses the charging of plug-in hybrid electric vehicles (PHEVs) in an existing office building microgrid equipped with a photovoltaic (PV) system and a combined heat and power (CHP) unit. Different charging strategies and charging power ratings for workplace charging are examined for their grid impact and their impact on the self-consumption of the locally generated electricity. The grid impact can be significantly reduced by using strategies that require limited future knowledge of the EV mobility behavior and limited communication infrastructure. These strategies allow a high number of EVs to be charged at an office building, even with a limited number of charging spots, due to the large standstill times.

Impact of Electric Vehicle On-Board Single-Phase Charging Strategies on a Flemish Residential Grid

This paper quantifies the impact of single-phase on-board charging strategies for electric vehicles (EVs) in a case study of a heavily loaded unbalanced Flemish three-phase low-voltage residential grid. Voltage droop charging and EV-based peak shaving, which do not need communication with the distribution grid, are modeled and the results are compared. The grid voltages are analyzed according to the probabilistic and deterministic limits of the EN50160 standard, for a 100% EV penetration rate. The impact on the EV user comfort is evaluated in terms of charging time and electrically driven distances. The chosen voltage droop charging eliminates critical voltages below 0.85 pu and reduces voltage unbalance, with a limited impact on the total charging time. EV-based peak shaving makes the grid fully compliant with EN50160 and avoids the need for an infrastructure upgrade. The electrically driven distances are not influenced by the charging strategies.

Comparative analysis of coordination strategies for electric vehicles

This paper gives a structured literature overview of coordinated charging of electric vehicles (EVs). The optimization objective, scale and method of each coordination strategy are the three parameters used to characterize and compare different approaches. The correlation between the three parameters and the research category are investigated, resulting in a correlation mapping of the different approaches.

Apartment Building Electricity System Impact of Operational Electric Vehicle Charging Strategies

This paper discusses the charging of multiple plug-in hybrid electric vehicles (PHEVs) in an apartment building, equipped with a photovoltaic (PV) system. Different charging strategies and charging power ratings are examined, which are assessed in terms of their grid impact, the self-consumption of local electricity generation, and the electric driving range. The impact of a residential building, which incorporates electric vehicle (EV) charging, on the distribution grid can be significantly reduced by using simple EV charging strategies. These strategies include complementing night-time with day-time charging, peak shaving at vehicle level, and charging the surplus of local generation. Effective results are obtained using only the knowledge of the present battery state of charge, next departure time, and the instantaneous local generation surplus. The simultaneity of the EV charging and the PV production increases. The increase in electric driving range is negligible for three-phase charging.

Integration of energy storage in distribution grids

Electrical energy storage services can bring benefit to multiple stakeholders in the distribution grid. Energy storage owners maximize their profit on an external energy market. This can cause a conflict with the distribution system operator because a grid is designed in terms of peak power, not energy. The subject of this paper is a optimization method for the siting and sizing of energy storage in distribution grids. The optimization is implemented multi-objective as to visualize the trade-offs between storage stakeholders and distribution system operators.

Impact-analysis of the charging of plug-in hybrid vehicles on the production park in Belgium

Internal combustion engines (ICE) are combined with electric motors and batteries in both hybrid electric vehicles (HEV) and plug-in hybrid electric vehicles (PHEV) to improve efficiency and achieve a limited all electric range. This paper determines the electrical power required for charging a fleet of PHEVs in Belgium. A stochastic model based on the driving behavior of Western European drivers, determines the availability of the PHEVs for grid charging.

A case study of coordinated electric vehicle charging for peak shaving on a low voltage grid

This paper discusses the impact of coordinated charging of electric vehicles for a peak shaving objective, through an online coordination algorithm, on low voltage grid constraints. The results for uncoordinated and coordinated charging are compared to assess the effect on the peak power demand. Furthermore, an unbalanced load flow analysis is performed on a real low voltage grid to assess the impact on the nodal voltages. The simulation results show a positive impact of coordinated charging for both the peak shaving objective and for voltage deviations. The results show that the coordination algorithm obtains effective results, while only needing a limited amount of communication, measurements and predictive knowledge.

Design Criteria for Electric Vehicle Fast Charge Infrastructure Based on Flemish Mobility Behavior

This paper studies the technical design criteria for fast charge infrastructure, covering the mobility needs. The infrastructure supplements the residential and public slow charging infrastructure. Two models are designed. The first determines the charging demand, based on current mobility behavior in Flanders. The second model simulates a charge infrastructure that meets the resulting fast charge demand. The energy management is performed by a rule-based control algorithm, that directs the power flows between the fast chargers, the energy storage system, the grid connection, and the photovoltaic installation. There is a clear trade-off between the size of the energy storage system and the power rating of the grid connection. Finally, the simulations indicate that 99.7% of the vehicles visiting the fast charge infrastructure can start charging within 10 minutes with a configuration limited to 5 charging spots, instead of 9 spots when drivers are not willing to wait.

Voltage droop charging of electric vehicles in a residential distribution feeder

Uncoordinated charging of electric vehicles may cause significant voltage deviations in some residential distribution grids. Grid voltage stabilizing load models, such as developed for distributed energy resources, can be applied to electric vehicle chargers as well. A fleet of 10 electric vehicles is considered, modeled according to current Flemish mobility behavior. For this fleet, different voltage droop load models for the chargers are discussed in terms of charging duration increase, grid losses and grid voltages. Load flow simulations are performed for a real and highly loaded residential grid in Belgium. In the worst case, the average charging rate is reduced to 0.847 pu of the nominal charging rate (4 kW). Accordingly, regardless of charging coordination, deviation from power set points will occur, thereby mitigating the impact on the grid. Furthermore, electric vehicle chargers equipped with voltage droop load models present robust, fault-tolerant behavior at times the coordination of the vehicles is hampered.