The Impact of EVs on the Electric Grid

May 14, 2022 by Harsha Korde

With gas prices rising, electric vehicles are becoming more popular, but transportation decarbonization remains a major issue.

With gasoline prices rising and the effects of climate change increasingly acute, transportation electrification is gaining steam in countries throughout the world. The benefits of a transition toward electric vehicles (EVs), and away from the compressed natural gas (CNG) fueling those with traditional internal combustion engines (ICEs), are many: reduced carbon emissions, less noise pollution, improved air quality and enhanced energy efficiency, among others. 


Planning for Electric Vehicles

That said, transportation decarbonization remains a significant issue in many countries whose power systems are dominated by fossil fuels. Though the switch to EVs will have direct repercussions for power grids, power system planning to assess EV impacts is practically nonexistent, leaving systems managers with an incomplete view of the technical and economic impact of EV integration. 


electric vehicle

Image used courtesy of Pixabay


As EVs increasingly supplant ICE-based vehicles, changing demands in power utilization will play an ever more critical role. These demands can have a range of impacts on the power network, such as an increase in the number of short circuit currents, and can lead to voltage level violations, in addition to affecting electrical equipment such as transformers. 

Chief among concerns is the load placed on the grid by EV charging. In a world where millions of EVs saturate the road, at any moment the grid could face an influx of stress from simultaneous, mass charging. That uncertainty makes it significantly harder for operators to balance grid supply and demand in real-time. At scale, an increased load on the distribution network impacts its power quality, and if EV batteries are charged without an analysis of their impact on the distribution network, it may directly result in an increase of energy unserved by the power system or the need for additional peak load capacity. 


The Distribution Level

To address this issue at the distribution level, different load management schemes should be implemented alongside existing distribution network policy, including time-varying tariffs and incentives for different charging behaviors. But even with these, the frequent connecting and disconnecting of high-current EV batteries pose its own challenges to the efficient operation of the electrical power system.

The net electrical energy utilized by EVs in a specific area is termed a “charging load curve” of EVs for that area. To analyze the impact of EV penetration on the electrical grid, the predictions provided by this load curve are essential. In impact evaluation, an EV load curve analysis can aid in evaluating various fundamental parameters of the electrical power distribution system, such as overloading, the impact on a domestic transformer, power loss in the system, the stability of the grid, fluctuations in voltage, power quality, and stress on distribution cables or conductors, and so on. Developing a full picture of those impacts as a result of EV charging is vital, as the prime objective here is to construct charging infrastructure integrated with the grid well enough to ensure smooth operation and maintenance of the distribution network.

When EV charging is carried out in a three-phase power system, it results in voltage imbalance, since those chargers are single-phase. Because of the increased load, the introduction of power electronics to the charging process also results in the injection of harmonics. This can be the cause of rising transformer temperatures at the distribution feeder, leading to wear of the transformer bushings. Harmonic distortion can as well affect the interruption capability of circuit breakers. These issues can be resolved via implementation of EV smart charging. 


V2G Technology

EV smart charging involves vehicle-to-grid (V2G) integration technology, allowing car batteries to give back to the power grid. In this way, the high-capacity batteries powering EVs can function as backup storage for the electrical grid. This type of setup utilizes bidirectional charging stations, where the power flow is directional based on the electricity demand at any given time. The extra energy can be used to power houses, buildings or anything connected to the power grid.

V2G integration technology has numerous benefits, such as improving the efficiency of power distribution. In a scenario where most EVs are charged simultaneously during peak hours, or at any time when energy demand is high, the system could easily be overloaded. With V2G technology, though, power companies can expand their capacity to meet these peaks; the bidirectional energy flow of V2G offers the most efficient model of power distribution. An additional benefit of this technology is the increase it could promote in renewable energy utilization, such as solar and wind, which will play an important role in sustaining the economy. Though these sources may be inconsistent, an efficient power grid can capture energy through them whenever needed and store it for distribution. Still, whenever there is a surge in energy capture, perhaps thanks to high winds, grid-level system storage has the potential to be maxed out. And that’s where EV batteries and V2G technology come in—with millions of EVs on hand ready to charge, there is additional room to capture and utilize this extra energy. When taken together, the above benefits also lead to another: cost stability. The more strain on the system, the higher the costs. Given that, the improved balance between energy supply and demand will naturally lead to less volatile pricing. 


An Uphill Battle?

All that said, there is still much work to be done in fully realizing bidirectional V2G integration technology. Today, most electric vehicles and charging stations are unidirectional, and converting them to the bidirectional form will require significant investment. There is also no standardized cadre of rules and regulations governing V2G integration technology, but rather a hodgepodge of electrical standards applied across varying jurisdictions, making the implementation of such technology difficult. In the face of these challenges, there is a lack of clear incentives for household and business customers to convert to smart charging systems. As such, in moving forward with an effective transition to true V2G integration technology infrastructure, a top priority is to address these obstacles.  


Feature image used courtesy of Pixabay