Overview:
The power distribution grid is greatly affected by the charging of electric vehicles (EVs). This is particularly visible when the coordination among the EVs is not well taken care of. If electric vehicles are charged in a way that is not coordinated, the power quality could be affected. If a good charging infrastructure isn't set up ahead of time, electric vehicles could cause substations to have to handle a lot more load. Charging electric vehicles in an uncoordinated manner can lead to generational adequacy difficulties as well as economic problems. Intelligent charging is necessary to avoid the exorbitant expenses of grid reinforcement. Fig. 1 illustrates the various issues faced when EV charging takes place in an uncoordinated manner.
Fig. 1. Various Effects of Uncoordinated EV Charging. Source: S. Tirunagaru et al.
Impact on grid congestion and network peak demand
The power distribution grid is greatly affected by the charging of EVs. This is particularly visible when the coordination among the EVs is not well taken care of. There are various levels of charging that taketakes place in EVs, ranging from Level 1 to Level 3 charging. Level 1 charging is slow charging, which can be done with a simple household charger. Level 2 charging is done through a dedicated EV charger, which can be placed in the garage. Level 3 charging is done through DC fast chargers.
All these chargers consume power that varies from 1.4 kW to 25 kW. When EVs are not workingcharged together, the peak demand caused by all of these chargers is a cause for concern. This is because the power distribution grid is unable to meet the demand, which leads to grid congestion. According to one study, just 10% of EVs on a grid increased peak demand by 17.9% of the current demand. When 20% of cars are electric, peak demand could go up by 36% compared to what it is now. It was also discovered that if EV penetration reaches 30%, peak demand on the electrical grid will increase by a whopping 53%.
Uncoordinated charging methods could raise the peak demand by 11.14 percent, according to a study conducted in California (USA), where EV penetration is 23%. According to a McKinsey study on EV integration in Germany, peak load might increase by 30% if charging is not coordinated when local EV adoption reaches 25%. Another study indicated that the introduction of 2.5 million electric vehicles in Turkey (representing 10% of the country's total automobiles) would raise peak demand by 12.5% if charging was not coordinated. These studies have proven the detrimental impacts of uncoordinated EV charging, particularly on the congestion of the power system and peak demand. So, these network congestion problems can be lessened by making sure electric vehicles are charged properly.
Impact on power quality
If electric vehicles are charged in a way that is not coordinated, the power quality could be affected. The voltage of the power system could go up or down depending on what happens when electric vehicles are charged. When the allowed range of voltage changes is exceeded past a certain point, it could cause problems. If something like this happens, the people who run the grid may have to pay a fine. Unbalanced voltage is another major problem that can happen, especially when working with systems with more than one phase.
Changes in the voltage on one side of the grid can have a big effect on the voltage on the other side of the grid. Harmonics and flickering can be serious problems when EV charging is not coordinated well. The power factor of the system is also hurt by electric vehicles being charged for long periods of time without being coordinated. When the right way to charge a lot of electric vehicles isn't followed, many pieces of equipment connected to the grids, like transformers, are more likely to break down.
Influence on power losses
Some energy is lost because of the infrastructure for charging electric cars, such as when batteries are being charged and drained. From the point of view of the person in charge of the distribution system, the power loss that happens while charging is an economic problem that needs to be fixed as soon as possible. So, transformer and feeder overloads can be kept to a minimum, at least to a certain degree. It was found that when there were 60% EVs on the road and different ways to charge them, the investment cost of the distribution network went up by up to 15%, and energy loss went up by up to 40% during off-peak hours.
Pillai and Bak-Jensen did research on how charging electric vehicles will affect Denmark's distribution network. According to the research, when there are 50% electric vehicles on the road and charging isn't coordinated, system losses go up by 40%. Deilami et al. did research to find out what happens to power losses when electric vehicles are being charged. Their findings revealed that power losses had increased for all uncoordinated charging scenarios. Habib and his colleagues found that random charging scenarios with level 2 charging conditions and a large number of EVs can have a big effect on the distribution network's parts, especially the power cables and power transformers, which can cause the system's losses to go up. All of these field trials and research studies have shown that charging electric vehicles (EVs) without coordination can cause power losses on the grid.
Other network issues
It is likely that large-scale use of electric vehicles would not be possible due to problems with generating enough power. Because of this, either new power-generating resources will have to be added to the grid, or coordinated charging schemes will have to be put in place. If a good charging infrastructure isn't set up ahead of time, the widespread use of electric vehicles could cause substations to have to handle a lot more load. Because of this, the capacity of the distribution grid might need to be increased in some way.
According to the findings of a study that was carried out in Barbados (with wind and solar generation supply accounting for 64% of the load demand and taking into consideration that there will be more than 26,000 EVs by the year 2030), uncoordinated charging results in an increase in generation costs that is five times higher than the most efficient smart charging strategies. Charging electric vehicles in an uncoordinated manner can therefore lead to generational adequacy difficulties as well as economic problems. As a result, intelligent charging is required to avoid the exorbitant costs of grid reinforcement that would result from uncoordinated EV charging.
Summarizing with key points:
- Losses in energy are caused in part by infrastructure for charging electric vehicles, such as the charging and discharging of batteries.
- When seen from the perspective of the operator of the distribution system, the power loss that occurs while charging is an economic concern that should be minimisedminimized.
- It was discovered that with a level of EV penetration of 60% and various charging schemes, there was an increase of up to 15% in the investment cost of the distribution network and an increase of up to 40% in energy losses during the off-peak hours.
- As a result, either new power generation resources will need to be commissioned into the grid, or coordinated charging schemes will need to be implemented.
- The widespread use of electric vehicles has the potential to considerably raise the load demand at substations if an adequate charging infrastructure is not established in advance.
- Intelligent charging is needed to avoid the huge costs of adding more power to the grid that would come from EVs charging at different times.
