Grid Impact


The grid impact of EV integration covers the spectrum of regulating power from EVs, electricity market for EV integration, EV charging management and demands and the impact of EV charging on power system operation.

Regulating power from EVs

EVs can be considered as distributed energy resources (DER) to handle the fluctuation from RES. An intelligent management of EV charging and discharging can achieve the goal of providing up and down regulating power from EVs to support reliable and secure operation of future power systems with high penetration of RES. The up and down regulating power capacities of DK West are shown below.

 
Fig. 1 DKWest Total UP Regulating Power from EVs with 3 phase, 16 A charging

 
Fig. 2 DKWest Down Regulation from EVs with 3 phase, 16 A charging

It is shown that the regulating power potential is very big with even 10% EV penetration.

Electricity market for EV integration

If EVs are introduced in the spot market, the market set-up is simple and possible today with an interval meter. If EVs are to participate in both the spot market and the regulating power market, a few more challenges have to be met. Requirements from the TSO regarding real time measurements of the individual unit and minimum bid size make it difficult for EVs to participate in the regulating power market today.

In addition to the wholesale market solutions, there are some challenges in relation to the local grid. Congestions in the local grid have to be taken into account with respect the behavior of the end-user.

EV portfolio management and grid impact study

The EV charging can be done in different ways, i.e. plug-and-charge (dumb charging), timed charging, and fleet operator based charging.

The EV charging demands of different charging scenarios have been obtained and analyzed. It is shown that the timed and fleet operator based charging demands are quite concentrated and may cause congestions in electric distribution networks.

                                                                                          

                                                                                        

 
Fig. 3 Aggregated EV power consumption with 1 Ph and 3 Ph charging

It has been observed that all the charging strategies can cause overloading on the 10 kV grid with 20% EV penetration and 3 Ph charging. This will cause problems in the distribution grid. The fleet operator has the ability to limit its consumption, however, with the current market setup, there are no incentives to do so. Therefore, information about such limitations will have to be conveyed by the DSO and solutions should be suggested by DSO– one possibility could be a future DSO congestion market.

 
Fig. 4 Transformer Loading 10 kV Ronne Syd– 20% EV penetration and 3 phase charging

 

Case studies with an arbitrary 5 MW limit on EV charging demands on the 60 kV level have been used to illustrate the effectiveness of using DSO congestion market limiting EV charging demands.


Fig. 5 Line Loading 60 kV – 20% EV penetration and 3 phase charging

 

  
Fig. 6 Line Loading 60 kV – 20% EV penetration and 3 phase charging with 5 MW limit