Wireless Charging Breakthrough: New Coil Design Stabilizes EV Power on Curves
In the fast-evolving world of electric mobility, one of the most persistent challenges has been ensuring seamless and stable power delivery during dynamic wireless charging. While static wireless charging systems have made significant strides in recent years, the real test lies in continuous charging while vehicles are in motion—especially when navigating turns. A new study from researchers at Shanghai Dianji University has tackled this critical issue head-on, introducing an innovative solution that could redefine the future of in-motion EV charging.
As cities grow smarter and transportation infrastructure evolves, dynamic wireless charging—where electric vehicles (EVs) charge while driving over embedded roadway coils—is emerging as a transformative technology. The promise is clear: extended driving range, reduced battery size, and less reliance on traditional charging stations. However, a major technical hurdle has limited its widespread adoption—power instability during turns.
When an EV equipped with a standard rectangular pickup coil enters a curved section of a wireless charging lane, the alignment between the vehicle’s receiver and the ground-based transmitter shifts. This misalignment reduces the magnetic coupling area, leading to fluctuations in mutual inductance. The result? Unstable voltage output, inefficient power transfer, and potential disruptions to onboard systems. Until now, this issue has remained a significant bottleneck in the development of reliable dynamic charging networks.
Enter a groundbreaking solution developed by Luo Qiang and Xu Fei from the School of Electrical Engineering at Shanghai Dianji University. Their latest research, published in a leading energy technology journal, introduces a novel compensation strategy using an embedded circular coil to maintain consistent power transfer even during sharp turns.
The team’s approach is both elegant and practical. Instead of relying solely on the conventional rectangular pickup coil mounted beneath the vehicle, they integrated a secondary, circular compensation coil within the main pickup system. This inner coil activates only when the vehicle enters a curved segment of the charging lane, effectively compensating for the loss in mutual inductance caused by misalignment.
What sets this research apart is not just the concept, but the rigorous scientific methodology behind it. The team didn’t stop at theoretical modeling—they combined genetic algorithms, electromagnetic simulations, and real-world experimental validation to fine-tune every aspect of the system. The goal was clear: minimize mutual inductance fluctuation to within ±0.5%, a threshold considered essential for stable power delivery in high-performance EV systems.
Using COMSOL Multiphysics and MATLAB/Simulink, the researchers first modeled the electromagnetic behavior of various coil configurations under different turning scenarios. They tested rectangular, hexagonal, and circular compensation coils, evaluating each based on mutual inductance stability, coupling efficiency, and resistance to lateral displacement. The results were unequivocal: the circular coil outperformed all others, delivering the smoothest and most consistent power transfer across a range of turning angles—from 45° to 180°.
But selecting the right coil shape was only the beginning. The next challenge was determining the optimal number of turns for the circular coil. Too few, and the compensation would be insufficient; too many, and the system could become overcompensated, leading to new instabilities. To solve this, the researchers turned to genetic algorithms—a computational method inspired by natural selection and evolution.
By simulating thousands of possible configurations, the algorithm converged on an ideal turn count that balanced performance across all common turning angles. After extensive iterations, the model identified 10 turns as the optimal number for the circular compensation coil. This single, unified specification proved effective across multiple curve geometries, eliminating the need for complex adaptive systems or multiple coil variants.
The real test came in physical validation. The team constructed a full-scale experimental platform operating at 20 kHz, with a 3 kW output power and a 380 V AC input. The setup included a three-phase inverter, rectifier circuit, compensation network, and a precisely engineered electromagnetic coupling system. As the test vehicle traversed a 90° curved charging lane, sensors recorded voltage, mutual inductance, and efficiency in real time.
The results were impressive. With the circular compensation coil engaged, mutual inductance fluctuation remained within ±0.4%—well below the targeted ±0.5% threshold. More importantly, the output voltage stabilized at 204 V, with a fluctuation rate of just 3.6% compared to the nominal 220 V. This level of stability is crucial for protecting sensitive vehicle electronics and ensuring consistent motor performance.
Equally significant was the finding that system efficiency peaked at a 20 cm air gap between the road and the vehicle’s pickup unit. This height represents a practical sweet spot—high enough to accommodate typical vehicle suspension travel and road clearance, yet close enough to maintain strong magnetic coupling. At this distance, the system achieved a peak efficiency of 93.4%, a figure that rivals many static wireless charging solutions.
The implications of this research extend far beyond laboratory success. For urban planners and transportation engineers, it offers a viable path toward deploying dynamic charging lanes in real-world environments, including intersections, roundabouts, and winding city streets. For automakers, it suggests a way to reduce battery size without compromising range, potentially lowering vehicle cost and weight.
Moreover, the use of a single, standardized compensation coil simplifies manufacturing and maintenance. Unlike adaptive systems that require complex sensors and control logic, this solution is passive and robust—activated only when needed, and effective across a wide range of conditions.
The study also sheds light on the importance of geometric design in wireless power systems. The researchers found that the ratio between the inner radius of the curved charging lane and its width—referred to as the proportionality coefficient Q—plays a critical role in determining inductance stability. When Q is less than 3, mutual inductance fluctuates significantly, making compensation essential. Since most real-world installations aim for compact footprints and lower construction costs, Q values between 1 and 2 are common, making the need for compensation even more pressing.
By addressing this reality, Luo and Xu’s work bridges the gap between idealized lab conditions and practical engineering constraints. Their solution doesn’t require rebuilding existing infrastructure; instead, it enhances current designs with a relatively simple add-on.
Another key insight from the research is the role of simulation and optimization in modern engineering. The integration of genetic algorithms with high-fidelity electromagnetic modeling allowed the team to explore a vast design space efficiently. This approach not only accelerated development but also ensured that the final design was globally optimized, not just locally acceptable.
From a sustainability perspective, the technology supports the broader adoption of electric vehicles by reducing range anxiety and charging downtime. If dynamic charging lanes become widespread, EVs could operate almost indefinitely on electrified roads, drawing power as they drive. This could be particularly transformative for public transit, delivery fleets, and autonomous vehicles that require high uptime and predictable energy availability.
The psychological impact on consumers should not be underestimated either. A system that delivers stable, uninterrupted power—regardless of road geometry—builds trust in wireless charging technology. Drivers are more likely to adopt EVs if they know their vehicles can charge seamlessly, even in complex urban environments.
While the current study focused on 90° turns, the principles apply to any curved path. The researchers note that their compensation coil design is scalable and can be adapted to different vehicle sizes, power levels, and roadway configurations. Future work may explore integration with vehicle-to-infrastructure (V2I) communication systems, allowing the compensation coil to activate automatically based on GPS or road signage data.
There are, of course, challenges ahead. Scaling the technology for mass deployment will require coordination between automakers, infrastructure providers, and regulatory bodies. Standardization of coil dimensions, operating frequencies, and safety protocols will be essential. Additionally, long-term durability testing under real-world conditions—such as exposure to weather, road debris, and mechanical stress—will be necessary before widespread adoption.
Nonetheless, the progress demonstrated by this research is undeniable. It represents a significant leap forward in making dynamic wireless charging not just a technological possibility, but a practical reality. By solving one of the most stubborn problems in the field—the instability of power transfer during turns—the team has removed a major barrier to the commercialization of in-motion charging systems.
The automotive industry has long sought ways to make EV ownership as convenient as internal combustion engine vehicles. This research brings us one step closer to that goal. Imagine a future where electric cars charge continuously as they drive, with no need to stop at charging stations, no range anxiety, and no disruption from road geometry. That future is no longer a distant dream—it is being built, turn by turn, on the foundation of innovative engineering like this.
As cities around the world invest in smart infrastructure, the integration of dynamic wireless charging into roadways becomes increasingly feasible. Pilot projects in countries like Sweden, Germany, and South Korea have already demonstrated the potential of the technology. With solutions like the one developed at Shanghai Dianji University, the transition from prototype to mainstream adoption accelerates.
In conclusion, the work of Luo Qiang and Xu Fei stands as a testament to the power of interdisciplinary research—merging electromagnetic theory, computational optimization, and hands-on experimentation to solve a real-world engineering challenge. Their circular compensation coil design is more than a technical fix; it is a step toward a more seamless, efficient, and user-friendly electric transportation ecosystem.
As the global push for decarbonization intensifies, innovations like this will play a crucial role in shaping the future of mobility. By ensuring that wireless charging works reliably in all driving conditions—not just on straight roads—this research helps pave the way for a truly sustainable transportation revolution.
Luo Qiang, Xu Fei, School of Electrical Engineering, Shanghai Dianji University, Journal of Electrical Engineering & Technology, DOI: 10.19753/j.issn1001-1390.2024.01.014