Understanding the relation between EV charging and power quality • EVreporter

EV charging stations, as power electronic devices, often introduce harmonic distortions into the power distribution networks. In this interaction, Shwetank Jain, Founder of Noida-based Belectriq Mobility (a leading manufacturer of EV Charging equipment), helps us understand the power quality issues related to EV charging.

What does the term “Power Quality” refer to?

The term “Power Quality” refers to the consistency and stability of the electrical power supplied to and used by electrical systems and equipment. It involves maintaining an optimal balance of voltage and current to ensure that electrical devices operate efficiently and without disruption. Power quality issues can arise from factors like voltage sags, surges, harmonics, unbalanced currents, and power factor problems, all of which can affect the performance of electrical equipment and the reliability of the power grid. In essence, good power quality means delivering a stable and clean electrical supply, minimizing disturbances that could harm devices or cause system inefficiencies.

Power quality standards should apply to both sides of the system: the energy delivered by the grid and the energy consumed by the devices using that power.

What power quality problems can arise from EV charging?

Electric vehicle charging systems rely heavily on switch-mode power supplies to convert AC to DC power for battery charging. This conversion process generates harmonics, primarily the 3rd, 5th, and 7th harmonics. The third harmonic, in particular, does not cancel out at the star point and accumulates in the neutral, significantly increasing the neutral current. This can cause overheating of the neutral wire and elevate the neutral-to-earth (NE) voltage, which may adversely affect other nearby electronic equipment.

Furthermore, while most loads are balanced, the random nature of charging patterns often leads to temporary imbalances across the three phases. Additionally, EV chargers, especially those with poor power factor correction, can introduce a leading power factor issue. This can further degrade the overall power quality, causing instability and inefficiencies in the electrical system.

These issues—harmonic distortion, neutral overheating, phase imbalances, and leading power factor—represent significant power quality concerns associated with EV chargers.

Do various types of chargers or charging patterns affect power quality differently?

Yes, different types of chargers and charging patterns can significantly impact power quality. Fast chargers, for instance, demand higher power, which can cause voltage drops, harmonic distortions, and flickers. Slow chargers generally have a lower impact but can still contribute high neutral currents and grid imbalances.

The low loading and minimal utilisation of charging stations right now is also adding to leading power factor issues.

Charging patterns also play a role—synchronized charging of multiple EVs can strain the grid, leading to voltage imbalances and frequency issues. In contrast, staggered or managed charging helps distribute the load more evenly, reducing power quality problems. Smart charging and V2G technologies can further mitigate these effects by balancing supply and demand dynamically.

When does EV charging reach a scale that significantly impacts power quality?

Currently, EV charging is in its early stages, with minimal impact on the grid. However, a significant surge in EV adoption and charging infrastructure is anticipated over the next decade, posing immense stress on the nation’s electrical systems. The demand for electricity is expected to nearly double, and as EV charging and renewable energy integration increase, grid stability will face growing challenges.

Proactive measures, including robust regulations and advanced equipment, are essential to mitigate the power quality issues arising from large-scale EV charging. Simultaneous charging of numerous EVs can lead to severe problems, such as unwarranted power consumption peaks, current distortion, transformer overloading, voltage drops, imbalance, and harmonic contamination. Additionally, residential EV charging will impose substantial single-phase loads on low-voltage (LV) distribution systems, further straining the grid. Addressing these challenges promptly is critical to ensuring grid reliability and sustainability.

How can CPOs (Charge Point Operators) reduce the impact of their charging setups on power quality?

Battery charging stations, as power electronic devices, often introduce harmonic distortions into distribution networks. Charge point operators can mitigate these effects by installing active power filters. These filters, connected in shunt on the AC side of EV chargers, address power quality issues by preventing harmonic distortion propagation and correcting leading or lagging power factors. This not only improves grid performance but also helps operators reduce energy costs. Also, the user should be careful during the design of EV charging stations to take care of such concerns at the initial stage itself.

How does EV charging affect the overall power distribution system?

EV charging can significantly impact the overall power distribution system in several ways. As the number of electric vehicles grows, the demand for electricity, especially during peak charging times, can place added strain on local grids. This can lead to:

• Increased Load Demand: High-power EV chargers, particularly fast chargers, draw substantial amounts of electricity, which can strain the existing distribution infrastructure if not properly managed or upgraded.

• Voltage Fluctuations: A large number of EVs charging simultaneously can cause voltage drops or fluctuations, potentially affecting the stability and reliability of the grid, especially in areas with older infrastructure.

• Load Imbalance: If EV chargers are not evenly distributed across phases or circuits, they can create load imbalances, which can cause inefficiencies and potentially damage equipment.

• Power Factor Issues: Many EV chargers, especially those with lower efficiency, can lead to a poor power factor, meaning the system is not utilizing the electricity effectively, causing higher losses and additional strain on the grid.

• Overloading: In areas with high EV adoption, there is a risk of overloading transformers and distribution lines, which may require costly upgrades to handle the increased demand.

Furthermore, it is essential for EVs and chargers to adopt V2G technology, enabling seamless grid integration. Also, adopting Demand load balancing plays a crucial role in improving the power quality by optimizing the distribution of electrical load, preventing grid instability, and mitigating power quality issues such as voltage fluctuations, harmonics, and overloading.

With proper control and communication systems, EVs can actively support the smart grid by providing ancillary services, including supply-demand balancing and voltage/frequency regulation.

Are there existing regulations to monitor and control the harmonic distortion caused by EV charging?

Yes, there are regulations to monitor and control harmonic distortion caused by EV charging.

• In India, the IEEE 519-2014 standard provides guidelines for harmonic limits applicable to LT and HT consumers, including EV charging systems.

• Additionally, kVAh-based billing, recommended by CEA and implemented in most states, indirectly addresses power factor deviations and penalizes users for poor power quality.

• Globally, SAE introduced power quality requirements for EV chargers in 2011 to address their impact on utility systems.

As interest in power quality and energy efficiency grows, efforts are underway to enhance EV charger specifications, ensuring they address power quality issues internally and comply with recommended practices.

This interview was first published in EVreporter Dec 2024 magazine.