I noticed that many studies which treat Electric Vehicle charging (in a V2X scenario) as an MILP (Mixed-Integer Linear Problem) problem, consider a constraint to prevent that an EV (Electric Vehicle) could simultaneous charge and discharge during the same time slot (the duration of this inteval varies from a study to another; the most used are: 15 minutes, 30 minutes; 1 hour).
I'm agree in considering that charging and discharging an EV at the same continuous time instant is not a realistic scenario, but which could be the reason of preventing this situation during a time inteval which lasts 15 minutes or 1 hour?
PS: I guess that it's done to simplify the complexity of the problem, but I'm wondering if there are other reasons.
Dear Luca Sefarini,
To elucidate the question you have to ask, i suggest you to see links and attached files on topic.
https://tel.archives-ouvertes.fr/tel-01876732/document
Article A Mixed Integer Linear Programming Model for Rolling Stock D...
Article A Mixed Integer Linear Programming Method for Optimizing Lay...
Article A Mixed Integer Linear Programming Method for Simultaneous M...
Article An Efficient Mixed Integer Linear Programming Model for the ...
Article A framework for home energy management and its experimental validation
Best regards
Dear Mohamed-Mourad Lafifi,
thank you for the answer.
Since my question isn't quite clear, I try to reformulate it by using two papers which you kindly shared.
The paper "Optimal Charging and Discharging Scheduling for Electric Vehicles in a Parking Station with Photovoltaic System and Energy Storage System" formulates the "EV charging optimization problem" as a MILP problem, by using time slots 15 minutes long. It states (at page 10): "Furthermore, an ESS cannot be charged and discharged at the same time period." So, by using the binary variable defined in Eq. (26), it prevents that an EV could be both charged and discharged within an interval of one slot; so, during one slot (15 minutes), the EV can only be charged OR discharged.
The same situation happens in "Optimization methods and energy management in ”smart grids”", where slot duration is 1 hour. Eq. (3.17), at page 69, represents the constraint which prevents that an EV could be both charged and discharged within a time period of one slot; so, during one slot (1 hour), the EV can only be charged OR discharged.
My point is: within an interval of 15 min (or 1 hour), I guess that it is reasonable that an EV could be charged during, for example, the first 10 min, and discharged during the remaining 5 min.
But since there are many academic papers which don't allow this, I'm wondering which could be the reason behind it.
I guess that it could have been done for a sake of simplicity, but I'm wondering if there are other reasons behind it.
Best regards.
To be clear, in practice, one could charge and discharge an EV battery simultaneously. Consider the case where you are using the EV's entertainment system and charging the battery.
As you've rightly noted, it simplifies the problem but the main reason would be safety concern (It is unsafe to continue to use a depleted battery), depending on the power demand, discharge rate would be faster than charging rate during operation. For a V2G case, it is a complete no.
Consider this case: If the energy source of the battery comes from a solar panel, this assumption might not necessarily hold.
Dear All,
I'm totally agree with colleague Paul Oke.
Best regards