Impact of EV battery chargers on the power quality of distribution systems

Abstract

A summary of the actual state of battery charger harmonics is presented. The effect of harmonic distortion on the distribution system, especially on distribution transformers, is analyzed. A program was developed, which allows the consideration of the transformer life consumption as function of the battery charger characteristics and charging algorithm. The program is considered a distribution planning and management tool. The proposed tool can be easily applied to determine the optimum charging time as function of the existing load, ambient temperature, and time of day. From the study, it can be deduced that direct connect-andcharge scheme can be detrimental to the transformer life, especially under high temperature and large load. Calculations show the existence of a quadratic relationship between the transformer life consumption and the total harmonic distortion (THD) of the battery charger current. Furthermore, the current THD should be limited to 25-30% in order to have a reasonable transformer life expectancy.

A Comprehensive Study of Key Electric Vehicle (EV) Components, Technologies, Challenges, Impacts, and Future Direction of Development

“…Voltage instabilities in such systems can occur because of load characteristics, and that instability can lead to blackouts. EV loads have nonlinear characteristics, which is different than the general industrial or domestic loads, and draw large quantities power in a short time period [82,128]. [129] corroborated to the fact that EVs cause serious voltage instability in power systems.…”

“…It also causes stress in the power system equipment like cables and fuses [128]. The present cabling is capable of withstanding 25% EV penetration if slow charging is used, in case of rapid charging, the amount comes down to 15% [132].…”

“…Elnozahy et al, stated that overloading of transformer can happen with 20% PHEV penetration for level 1 charging, whereas level 2 does it with 10% penetration [152]. According to [128], charging that takes place right after an EV being plugged in, can be detrimental to the transformers.…”

Charging Electric Vehicles in the Smart Grid

“…BEVs and Plugin HEVs (PHEVs) are charged through the electric power system, which can lead to increased congestion of the grid. Especially the impact on the low voltage grid can be significant, if the peak of arriving EVs that plug in to charge at home corresponds to the residential load peak (Clement-Nyns et al (2010); Gomez and Morcos (2003); see also Section 3).…”

Price based electric vehicle charging

“…Impact of EV charging on Portuguese grid and Indian grid has been presented in [10] and [11], respectively. Impact of EV charging on transformer life and total harmonic distortion is presented in [12], [13]. Hence, it is necessary to devise EV charging algorithms to reduce the impact on the power grid.…”