Improved Wireless Charging for EVs on Curves Boosts Efficiency
As the global electric vehicle (EV) market continues its rapid ascent, one of the most persistent challenges remains the limitations of battery range and charging infrastructure. While advancements in battery technology have extended driving distances, the need for convenient, fast, and seamless charging solutions has become a critical focus for automakers, researchers, and urban planners alike. Among the most promising innovations in this domain is dynamic wireless charging (DWC)—a technology that enables EVs to charge while in motion, effectively eliminating range anxiety and reducing dependence on large, heavy battery packs. However, despite significant progress, practical implementation of DWC systems has faced technical hurdles, particularly when vehicles navigate curved roadways.
A recent breakthrough by a team of researchers from the School of Mechanical and Electronic Engineering at Wuhan University of Technology has addressed a key obstacle in the deployment of dynamic wireless charging systems: the sharp drop in power transfer efficiency at road curves. Their findings, published in the Journal of Power Supply, demonstrate a novel coil design that significantly improves energy transmission on curved tracks, marking a pivotal step toward the real-world viability of in-motion charging.
The research, led by Zhu Guofu and conducted in collaboration with Li Jiangui, Wang Longyang, Li Qiang, Chen Chen, and Liu Shan, zeroes in on a fundamental issue in current dynamic wireless charging setups. Most existing systems rely on segmented rail structures—discrete sections of transmitting coils embedded beneath the road surface. As an EV moves along the roadway, these segments are activated in sequence, creating a relay-like effect that powers the vehicle continuously. While this approach minimizes electromagnetic leakage and energy loss compared to continuous long rails, it introduces a critical flaw at transition points, especially on curves.
When a vehicle enters a curve, the geometry of the road causes misalignment between the onboard receiving coil and the ground-based transmitting coils. In traditional rectangular coil designs, the outer edge of the curve has a larger radius than the inner edge, creating a widening gap between adjacent transmitting segments. This spatial mismatch reduces the magnetic coupling between the primary (transmitter) and secondary (receiver) coils, leading to a phenomenon known as mutual inductance drop. As mutual inductance decreases, so does the system’s ability to transfer power efficiently, resulting in a noticeable decline in charging performance—sometimes by as much as 10% or more at maximum deviation.
“This mutual inductance drop is particularly pronounced on curves, where the angular misalignment between coils is at its peak,” explained Professor Li Jiangui, the corresponding author of the study. “While much research has focused on optimizing straight-track performance and compensation topologies, the challenge of maintaining efficiency on curved paths has been underexplored. Our work aims to close that gap.”
The team’s approach began with a rigorous theoretical analysis of the relationship between coil orientation and mutual inductance in curved environments. By modeling the spatial dynamics of the transmitting and receiving coils during a turn, they were able to quantify how angular deviation—measured in degrees—affects magnetic flux linkage and, consequently, power transfer capability. Their analysis confirmed that as the vehicle’s receiving coil rotates relative to the transmitting rail, the effective coupling area diminishes, leading to a nonlinear decline in mutual inductance.
Armed with this insight, the researchers proposed a redesigned transmitting coil structure tailored specifically for curved road segments. Rather than using standard rectangular coils with straight outer edges, the new design features a contoured geometry that conforms to the curvature of the road. By aligning the outer perimeter of the transmitting coil with the arc of the bend, the distance between adjacent coil segments is minimized, ensuring a more consistent magnetic field distribution across the transition zone.
“This isn’t just a minor tweak—it’s a rethinking of how we lay out the transmitting infrastructure on curves,” said Zhu Guofu, the lead researcher. “By shaping the coil to match the road’s radius, we maintain a uniform gap between segments, which in turn preserves the magnetic coupling and reduces flux leakage.”
The modified coil retains the same width and internal dimensions as its predecessor, ensuring compatibility with existing system parameters and vehicle-mounted receivers. However, its outer edge is subtly curved, allowing for a smoother handoff of power from one segment to the next as the vehicle rounds the bend. This design innovation does not require changes to the vehicle-side hardware, making it a cost-effective upgrade for future DWC deployments.
To validate their concept, the team conducted extensive finite element simulations using industry-standard electromagnetic modeling software. The simulation environment replicated a full-scale dynamic charging scenario, with a receiving coil moving through a curved track segment at varying angles of deviation—from 0 degrees (perfect alignment) to ±3.5 degrees (representing maximum lateral and angular offset). The results were striking: at the peak deviation angle, the improved coil design demonstrated a mutual inductance value nearly 15% higher than the conventional rectangular layout.
Encouraged by the simulation outcomes, the researchers constructed a physical test platform to evaluate the system under real-world conditions. The experimental setup included a DC power source, a high-frequency inverter operating at 85 kHz, an LCC-S compensated resonant circuit, the custom-designed transmitting and receiving coils, and an electronic load to simulate battery charging. The LCC-S topology was selected for its superior current regulation and reduced switching losses, making it well-suited for high-power EV applications.
During testing, the team measured system efficiency across the same range of angular offsets, comparing the performance of the original and modified coil structures. At zero deviation, both configurations performed similarly, with efficiencies differing by less than half a percent—indicating that the new design does not compromise straight-track performance. However, as the angle increased, the advantages of the improved coil became evident.
At the maximum offset of 3.5 degrees, the conventional system achieved a transmission efficiency of 49.55%, while the modified system reached 58.21%—an improvement of 8.66 percentage points. “That may sound modest in isolation, but in the context of high-power, high-efficiency systems, an 8.66% gain is substantial,” noted Wang Longyang, a doctoral candidate involved in the project. “When you’re dealing with tens of kilowatts of power over kilometers of roadway, even small efficiency gains translate into significant energy savings and reduced infrastructure costs.”
The results were consistent across multiple test runs, with the efficiency improvement averaging between 8% and 9%, confirming the robustness and reproducibility of the design. Moreover, the team observed that the enhanced magnetic coupling also contributed to more stable output power, reducing fluctuations that could stress the vehicle’s power management system.
The implications of this research extend beyond academic interest. As cities and transportation agencies explore the feasibility of embedding wireless charging lanes into highways and urban roads, the ability to maintain high efficiency on curves is essential. Interchanges, cloverleafs, and winding mountain roads—all common features of modern road networks—require charging infrastructure that can perform reliably under non-ideal alignment conditions. The Wuhan team’s coil design offers a practical solution that could accelerate the adoption of dynamic wireless charging in real-world environments.
Industry experts have taken note. “This work addresses a real pain point in the deployment of dynamic charging systems,” said an independent power electronics engineer familiar with the study. “Most prototypes focus on idealized straight-line performance, but roads aren’t straight. Any technology that improves efficiency on curves brings us closer to a truly seamless charging experience.”
The research also aligns with broader trends in sustainable transportation. By enabling smaller batteries and continuous charging, dynamic wireless systems can reduce the overall weight of EVs, improve energy efficiency, and lower the demand for raw materials used in battery production. Furthermore, the ability to charge while driving supports the development of autonomous electric fleets, which require minimal downtime for recharging.
Looking ahead, the team plans to expand their research to include more complex road geometries, such as sharp turns, multi-lane curves, and variable-radius bends. They are also investigating adaptive control strategies that could further optimize power delivery based on real-time vehicle positioning and speed. Additionally, they are exploring the integration of their coil design with smart grid technologies, enabling bidirectional energy flow and vehicle-to-grid (V2G) capabilities.
The success of this project underscores the importance of interdisciplinary collaboration in advancing clean energy technologies. By combining expertise in electromagnetic theory, mechanical design, power electronics, and system integration, the Wuhan University of Technology team has delivered a solution that is both scientifically rigorous and practically applicable.
As governments worldwide push for decarbonization of the transportation sector, innovations like this bring the vision of a fully electrified, wirelessly charged future one step closer to reality. The road to sustainable mobility is not just about better batteries or faster chargers—it’s about reimagining how vehicles interact with the infrastructure around them. With continued advancements in dynamic wireless charging, the dream of driving without ever needing to stop for a charge may soon become an everyday experience.
The study, titled Research and Improvement of Mutual Inductance Drop at Corner in Dynamic Wireless Charging System for Electric Vehicles, was published in the Journal of Power Supply, Volume 22, Issue 4, July 2024, with DOI: 10.1324/j.issn.2095-2805.2024.4.228. The authors are Zhu Guofu, Li Jiangui, Wang Longyang, Li Qiang, Chen Chen, and Liu Shan from the School of Mechanical and Electronic Engineering at Wuhan University of Technology.