Grid integration of EVs- Issues and challenges
Integration of electric vehicles (EV) with the grid is essential for accelerating the adoption of EVs in India. EVs offer a promising solution for reducing emissions from the transportation sector, which is the second-largest contributor to India’s greenhouse gas emissions. However, as EV penetration increases, the demand for EV charging stations will also increase, creating challenges for the conventional power sector. Integration of EV charging infrastructure with distribution grids presents both challenges and opportunities for the power sector.
One of the key challenges faced in integrating EV charging infrastructure with the grid is voltage stability issues. The distribution network is more susceptible to voltage sags due to high power drawn, which may even surpass the stable voltage operating zones. As EV charging entails a higher power demand compared to other residential loads, high penetration of EVs will significantly increase the power demand in low voltage grids, potentially leading to voltage stability issues. Moreover, EV charging may coincide with other loads in the system, further aggravating the voltage stability issue.
Phase imbalance is another challenge unique to India. The 2W and 3W electric vehicle sector has seen massive growth and is expected to dominate national sales. However, these vehicles are generally charged using single-phase chargers. If these chargers are not uniformly distributed among the phases of the distribution network, it may lead to unbalanced phase voltages and current loading, which results in higher losses in the network and voltage issues.
Uncontrolled EV charging could increase the peak load on the grid, potentially contributing to overloading of transmission system and distribution network assets like transformers and cables. This extra load would also lead to increased generation and, therefore, increase the electricity price. It could also stress the system with an increased requirement of ramp limits.
Overloading is another challenge that arises from the coincidence of EV charging with the network peak load. This increased EV load can cause overloading in different assets of the distribution network, such as distribution transformers, cables, fuses, etc. This overloading can significantly reduce the lifespan of the equipment while simultaneously reducing the efficiency of energy transmission.
Power losses in the distribution network generally refer to the I2R losses of the overhead lines/underground cables. Therefore, the total power loss in the system increases with added current flowing through the lines due to the extra EV charging load, making the supply of power less efficient. Besides, unbalanced loading can lead to uneven losses among the three phases.
EV chargers, which are basically AC/DC and DC/DC converters, are power electronic converter-based devices that act as non-linear loads in the system and introduce voltage and current harmonic distortions into the supply. The level of distortion is proportional to the number of EV chargers operating simultaneously in the distribution network. Moreover, EV chargers bring voltage excursions which end-use customers can detect as flickers in their lighting devices or change in speeds in the electrical motors.
In conclusion, grid integration of EVs presents both challenges and opportunities for the power sector. The key challenges include voltage stability issues, phase imbalance, increase in peak load, overloading, power losses, and power quality. Addressing these challenges requires a collaborative effort from the government, utilities, EV manufacturers, and charging infrastructure providers. However, the benefits of integrating EVs with the grid, such as reducing emissions and improving energy security, outweigh the challenges.