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This lecture discusses the integration of electric vehicles (EV) into the electrical grid. The following topics will be addressed:

• The current trends in the adoption of EV
• The types and power ratings of EV chargers
• The impact of mass deployment of EV’s on the electricity grid

The current trends in the adoption of EV

According to the International Energy Agency, there were 11 million electric vehicles around the world in 2020, which has increased steadily over the past decade. China has the most electric vehicles and is followed by Europe and the USA.

In the Netherlands, the number of electric vehicles (this includes all vehicles with an electric battery, a plug-in hybrid electric vehicle or a fuel cell electric vehicle) has become three times as much in the period 2016-2020. Also, in 2020 around 20% of all vehicles sold was an electric vehicle. In 2030 all the new cars have to be emission-free in the Netherlands.

Due to an increase of electric vehicles, the demand for charging stations and points has also increased. Therefore, the number of public charging stations has also increased rapidly, which has the same growth rate as the number of electric vehicles. The ratio of vehicles to charging stations is maintained at 4 to 1.

The types and power ratings of EV chargers

The size of an electric vehicle ranges from these of small two-wheelers and goes up until the ratings of electric busses and trucks. In between, there are the three-wheelers and normal electric vehicles, which have their own energy rating and distance range. The energy ratings and distance ranges of the different vehicles is shown in the table below.

Electric vehicle	Energy rating [kWh]	Distance range [km
Two-wheelers	1-5	50-125
Three-wheelers	10-30	75-150
Car batteries	30-100	200-500
Bus & Trucks	50-500	50-200

 

 

 

This means that it can take several hours to charge EV batteries because of the large capacity. However, the battery capacities and ranges that are shown are general and will vary from vehicle to vehicle based on its application.

For AC charging, the AC power from the electric grid is fed to the AC-DC converter, which is inside the EV. This converter converts the AC power into DC power, which is suitable for charging. However, due to restrictions on size and weight of an on-board converter, the maximum charging power is usually 22 kW. There are three types of AC charges, which are shown in the table below. Type 1 is commonly used in the USA and Japan, and type 2 is widely used in Europe. The last type of AC charger is from Tesla.

Charger	Voltage [V]	Maximum current [A]	Maximum power [kW]
Type 1 (J1772)	120	16	1.9
	240	80	19.2
Type 2 (Mennekes)	230	16	3.7
	400	32	22
	400	63	43
Tesla	240	48	11.5

 

 

To increase the charge rating, the converter can be moved off-board. This is referred to as DC charging, and the maximum charging rate is between 50 and 350 kW. There are also different types of DC chargers, which are shown in the following table.

Charger	DC Voltage [V]	Maximum current [A]	Maximum power [kW]
COMBO/CSS	200-1000	350	350
CHAdeMo	200-1000	400	400
Tesla US	500	300	120
	500	600	250
Chaoji	200-1500	600	900

 

The last type of charger (Chaoji) is a newly proposed charger, which increases the maximum power rating even further.

The impact of mass deployment of EV’s on the electricity grid

To understand the relevance of electric vehicles for the electricity grid, the power rating of different household appliances can be compared to the charge ratings of EV. Normal household appliances, such as phones, TV’s or washing machines have a power rating in order of 1-3 kW. This is much smaller than the charging rates of EV’s that were just discussed. This means that EV charging will significantly increase the power demand from the electric grid, which will be in addition to the increased demand from the electrification of heating. Also, charging an electric vehicle will last several hours, which is likely to have overlap with electric vehicles in the neighbourhood.

This increase of grid demand can have the following effects on the electricity grid:

• Overloading of the lines.
• Overloading of the transformers.
• Over- or undervoltage, which can happen in networks with long feeder cables. Overvoltage occur if power is flowing upstream into the grid. This can be either due to EV storage flowing into the grid or PV panels generating too much power that is not used by the EV’s, leading to an upstream power flow.
• Phase imbalance, which can happen in a 3-phase network in there is an imbalance of EV charging on one or two phases.
• Harmonic injections, due to the high switching frequencies of the power electronic converters.

Conclusion

This lecture introduces the integration of electric vehicles. First, the significant increase of EV’s and electric charging stations was discussed, which was followed by a discussion on different types of electric vehicles. Finally, the different effects on the electric grid were mentioned.