6.2 Seven percent EV adoption
6.3.1 Dumb charging with balanced allocation
As in the previous section, the EVs are first assumed to be placed more or less evenly across the system nodes, spreading the additional demand on the power system. The charging loads are based on observed charging patterns as in earlier scenarios and the results are presented in Figure 6.13. Comparing the graph with the results obtained in the previous section (Figure 6.5), it is obvious that
6.3 20 percent EV adoption 42
Figure 6.12: Allocation used for the balanced allocation scenarios with 20 percent EV adoption.
the increased degree of EV penetration has affected the voltage level. Still, the difference is not as large as one might have expected. With a total of 16 EVs spread out across the residential area, and charging more or less simultaneously, the voltage levels at the various nodes in the system are still well within the limits. In conclusion, with the assumptions given in this scenario, the system appears to be capable of handling the increased peak power consumption.
43 Chapter 6 Results 0 2 4 6 8 10 12 14 16 18 20 22 24 0.9 0.92 0.94 0.96 0.98 Hours Voltage (p.u.)
Figure 6.13: Voltage lev- els with 20 percent EV adop- tion, spread allocation of EVs
and dumb charging.
0 2 4 6 8 10 12 14 16 18 20 22 24 0.9 0.92 0.94 0.96 0.98 Hours Voltage (p.u.) Residence 24 Residence 33 Residence 16 Residence 2 Residence 23
Figure 6.14: Voltage levels with 20 per- cent EV adoption, spread allocation of
EVs and smart charging.
6.3.2
Smart charging with balanced allocation
As in section 6.2, smart charging is not necessary to satisfy the voltage level re- quirements under the assumptions given in this scenario. However, the smart charging algorithm makes the voltage curve smoother and consumption more con- stant.
6.3.3
Dumb charging with imbalanced allocation
The 16 EVs are now located at residences connected to the F branch of the grid. This high concentration of EVs in one part of the system will increase the local energy consumption significantly. The EVs are distributed so that the 15 residences on node F2, F3 and F4 have an EV connected, and one of the residences on F1 has been given one as well. That gives a total of 16 EVs located in close proximity, with the same charging pattern as earlier. As previous results have indicated, F4 is much more vulnerable to load increase than the other nodes. As indicated by Figure 6.16, the voltage level in F4 drops below the limit. This discovery is not surprising since the node voltage dropped to an unsatisfactory level in the previous scenario with seven percent EV integration as well. An interesting observation however, is that the voltage levels in nodes F2 and F3 stay above the limit for the entire simulation period. Even though all residences connected to the nodes have EVs charging, the nodes retain acceptable voltage levels. This suggests that the grid is strong on this location, and able to handle a large load increase without violating the given system limits.
6.3 20 percent EV adoption 44
Figure 6.15: Allocation used for the imbalanced allocation scenarios with 20 percent EV adoption.
6.3.4
Smart charging with imbalanced allocation
By applying smart charging in the system, all nodes retain a voltage level within the boundaries of the system. The result indicates that a 20 percent EV penetra- tion of the system is possible, even if the EVs are located in close to one another. Comparing Figure 6.16 and Figure 6.17, it is obvious that smart charging strate- gies can have a great effect on the voltage levels in a power grid when the degree of penetration increases. Residences 41, 32 and 56 retain a stable voltage level through the simulation period, which indicates that these nodes would be able to handle a even larger EV adoption share.
45 Chapter 6 Results 0 2 4 6 8 10 12 14 16 18 20 22 24 0.9 0.92 0.94 0.96 0.98 Hours Voltage (p.u.)
Figure 6.16: Voltage lev- els with 20 percent EV adop- tion connected to node F4
and dumb charging.
0 2 4 6 8 10 12 14 16 18 20 22 24 0.9 0.92 0.94 0.96 0.98 Hours Voltage (p.u.) Residence 41 Residence 32 Residence 56 Residence 23
Figure 6.17: Voltage levels with 20 per- cent EV adoption connected to node F4
and smart charging.
6.4
50 percent EV adoption
50 percent EV adoption is a very distant scenario compared with the degree of adoption we have in Norway today. However, it is likely that the share of EVs will be higher than average in urban areas, and lower in more remote location. So, an EV share of 50 percent is not unrealistic in some areas in the future. In any case, it is interesting to observe how a really large adoption share will affect the power system. 557 EVs will be added to the model, and 40 of these are placed at the low voltage part. With this level of EV adoption, 65 percent of all residences will have an EV connected assuming spread allocation.
6.4.1
Dumb charging with balanced allocation
Assuming 40 EVs added to the residential area, the added loads constitute a significant share of the total consumption. Figure 6.18 indicates that the voltage levels in branch C, D, E and F will drop below the limit of the system restriction. This observation implies that the system is not capable of handling the charging loads without implementing smart charging.
6.4.2
Smart charging with balanced allocation
Applying smart charging strategies in the system mitigates the voltage fluctua- tions. Under the conditions presented in this scenario, it appears that the system is able to accommodate the charging loads of a 50 percent EV share. The imple- mentation of smart charging strategies will undoubtedly mitigate the stress put on the power grid, especially for a high EV penetration level.
6.4 50 percent EV adoption 46 0 2 4 6 8 10 12 14 16 18 20 22 24 0.9 0.92 0.94 0.96 0.98 Hours Voltage (p.u.)
Figure 6.18: Voltage lev- els with 50 percent EV adop- tion, spread allocation of EVs
and dumb charging.
0 2 4 6 8 10 12 14 16 18 20 22 24 0.92 0.93 0.94 0.95 0.96 0.97 0.98 0.99 Hours Voltage (p.u.) Residence 24 Residence 33 Residence 16 Residence 2 Residence 23
Figure 6.19: Voltage levels with 50 per- cent EV adoption, spread allocation of
EVs and smart charging.
Figure 6.20: Power through main cable in F branch assuming 50 per- cent EV adoption and dumb charg-
ing.
Figure 6.21: Power through main cable in F branch assuming 50 per- cent EV adoption and smart charg-
ing.
6.4.3
Dumb charging with imbalanced allocation
Assuming imbalanced allocation, the 40 EVs are divided between the 21 residences in branch F. This means that there are 2 EVs placed on almost every residence in this part of the system. Although most families that decide to purchase an electric car have a fossil-fueled car in addition, it is not unlikely that some families choose to have two electric cars instead. From Figure 6.22 it is obvious that the additional load during peak hours causes more stress than the grid can handle. Additionally, the power consumption of this many electric vehicles charging si- multaneously causes the total consumption to exceed the branch cable thermal limit. The characteristics of the main cable between the substation and branch F has a given maximum current of 435 amps. In a three-phase 230 V system with cosφ=0.98 that allows a maximum power flow of 170 kW. This limit is marked in Figure6.20 and 6.21 with a black line.
47 Chapter 6 Results 0 2 4 6 8 10 12 14 16 18 20 22 24 0.86 0.88 0.9 0.92 0.94 0.96 0.98 Hours Voltage (p.u.)
Figure 6.22: Voltage lev- els with 50 percent EV adop- tion connected to node F4
and dumb charging.
0 2 4 6 8 10 12 14 16 18 20 22 24 0.86 0.88 0.9 0.92 0.94 0.96 0.98 Hours Voltage (p.u.) Residence 41 Residence 32 Residence 56 Residence 23
Figure 6.23: Voltage levels with 50 per- cent EV adoption connected to node F4
and smart charging.
6.4.4
Smart charging with imbalanced allocation
By applying smart charging in the system, the thermal power flow through the branch cable is below the maximum limit at all times during the simulation. The voltage drops are also mitigated. The voltage levels at nodes F1, F2 and F3 are within the specified limits for the duration of the 24 hours. However, the voltage level at residence 23 still drops below the minimum allowed voltage level several times. The result suggests that with the given allocation, 50 percent adoption of EVs are more than the grid connecting the residences at F4 can handle. If an EV penetration this high becomes realistic in this part of the system, other actions in addition to smart charging must be taken to retain desired system parameters.