Revolutionary Drive Multiplexing Boost Technology Bridges the Gap Between High-Voltage EVs and Low-Voltage Charging Infrastructure
The automotive industry is in the midst of a profound transformation, with electric vehicles (EVs) at the forefront of efforts to reduce carbon emissions and dependence on fossil fuels. A key trend in this evolution is the shift toward 800 V high-voltage architectures, which promise to deliver faster charging times, improved energy efficiency, and enhanced overall performance. However, this transition has been hampered by a critical challenge: the existing charging infrastructure, dominated by 400 V low-voltage DC charging piles, struggles to keep pace with the new high-voltage vehicle designs.
In a groundbreaking development, researchers from leading institutions have introduced an innovative solution that addresses this compatibility issue head-on. Their work, titled “Multiplexing Booster Technology for Electric Vehicle Drive,” presents a novel time-sharing multiplexing step-up charging topology and control strategy that enables 800 V high-voltage EVs to seamlessly use existing low-voltage charging infrastructure. This breakthrough not only enhances the practicality of high-voltage EVs but also represents a significant step forward in optimizing resource utilization and reducing costs in the EV ecosystem.
The Urgency of Compatibility in the EV Transition
As concerns over climate change and fossil fuel depletion intensify, governments and industries worldwide have embraced electric vehicles as a cornerstone of sustainable transportation. In China, for instance, policymakers have implemented a range of supportive measures, emphasizing that new energy vehicles are pivotal to the nation’s ambition to transition from a major automobile producer to a global automotive powerhouse. This commitment has driven rapid advancements in EV technology, with 800 V high-voltage architectures emerging as a key area of innovation.
Vehicles equipped with 800 V systems, such as the Porsche Taycan, Hyundai Ioniq5, and models from domestic Chinese manufacturers like Xpeng, Li Auto, BYD, and GAC, offer compelling advantages. These include shorter charging durations, higher power output, and more efficient energy usage. However, the widespread adoption of these vehicles has been hindered by the slow rollout of compatible high-voltage charging infrastructure.
Statistics reveal that the vast majority of existing DC charging piles operate on 500 V or lower platforms, with over 93.3% of public fast-charging stations for private cars falling into this category. High-voltage charging stations, on the other hand, require significant investments in grid upgrades and have higher construction costs, leading to their delayed deployment. This disconnect between vehicle technology and charging infrastructure creates a pressing need for solutions that allow high-voltage EVs to utilize existing low-voltage charging facilities.
A Novel Approach: Drive System Multiplexing
Recognizing this challenge, a team of researchers has developed a pioneering solution that leverages the inherent characteristics of EV drive systems. The core insight is that a vehicle’s drive system and charging system do not operate simultaneously. By strategically reconfiguring the drive system to function as a charging booster when the vehicle is stationary, the researchers have created a way to eliminate the need for separate charging hardware, thereby reducing costs and saving space.
The proposed technology transforms the electric motor and its inverter into a high-power boost converter during charging. Specifically, the motor windings act as energy storage inductors, while the motor’s inverter controller is repurposed as a chopper switch controller. By incorporating just two relay switches and a small number of passive components, the system can seamlessly switch between driving and charging modes.
In charging mode, the system operates as a three-phase interleaved parallel Boost circuit. This configuration allows for efficient conversion of the 450 V output from a standard low-voltage DC charger to the 880 V required by high-voltage vehicle batteries. The use of interleaved parallel technology helps to minimize current ripple, ensuring stable and efficient power transfer.
Overcoming Technical Challenges: Modeling and Control
A key challenge in developing this technology lies in understanding and managing the complex electromagnetic characteristics of the motor windings when used as inductors. The researchers conducted a detailed analysis of the coupling relationships between the three-phase windings of an embedded permanent magnet synchronous motor (PMSM), which is commonly used in EVs.
They developed mathematical models to describe how the inductance of each phase winding changes with the rotor position. This analysis revealed that the inductance values exhibit periodic variations, which can affect the performance of the boost converter. To address this, the team introduced an external inductor to counteract the negative effects of mutual inductance between the windings, ensuring consistent and reliable operation across all rotor positions.
Equally critical to the system’s performance is the control strategy. The researchers compared traditional dual-loop control methods with a more advanced approach combining proportional-integral (PI) control and model predictive control (MPC). The dual-loop control, while effective in some scenarios, was found to have limitations in terms of response speed and parameter tuning complexity.
In contrast, the proposed PI-MPC hybrid control strategy offered significant advantages. By retaining the PI regulator for voltage control to ensure steady-state accuracy and incorporating MPC for current control to enhance dynamic response, the system achieved rapid and stable performance. The MPC component predicts future system states and selects the optimal switching actions to minimize current ripple and maintain voltage stability, even during sudden load changes or input voltage fluctuations.
Validation Through Simulation and Experimentation
To verify the effectiveness of their approach, the researchers conducted extensive simulations and experiments. Using Simulink, they built a detailed model of the system and tested its performance under various conditions. The simulations compared the dual-loop control and PI-MPC hybrid control strategies across different rotor positions, evaluating metrics such as current ripple, response time, and stability.
The results demonstrated that the PI-MPC hybrid control strategy outperformed the traditional approach, particularly in dynamic scenarios. For example, when the load suddenly changed, the hybrid control system achieved stable operation in approximately 8.66 ms, compared to 12.03 ms for the dual-loop control. Similarly, in response to input voltage fluctuations, the hybrid control system settled 80% faster, with significantly less overshoot.
To further validate their findings, the researchers constructed a 50 kW experimental platform. This platform included a 250 kW embedded PMSM, a main power controller, external inductors, and various measurement instruments. The experiments confirmed the simulation results, demonstrating that the system could reliably boost voltage from 250 V to 400 V (scaled for the experimental setup) with efficient and stable operation.
The experimental data showed that the system maintained low current ripple across different operating conditions, with input current ripple well within acceptable limits. The PI-MPC control strategy again proved superior in dynamic tests, with faster response times and smaller voltage fluctuations during load changes compared to the dual-loop control method.
Implications for the EV Industry and Beyond
The successful development of this drive multiplexing boost technology holds significant implications for the electric vehicle industry. By enabling high-voltage EVs to use existing low-voltage charging infrastructure, it removes a major barrier to the widespread adoption of advanced EV architectures. This, in turn, can accelerate the transition to more efficient, longer-range electric vehicles without requiring massive investments in new charging infrastructure.
The technology also offers substantial economic benefits. By eliminating the need for a separate onboard charger, it reduces the cost, weight, and space requirements for EVs. This can make electric vehicles more affordable and appealing to consumers, further driving market penetration. Additionally, the improved utilization of existing components and infrastructure enhances the overall sustainability of the EV ecosystem.
Looking beyond passenger vehicles, this technology could find applications in other electric mobility sectors, such as commercial trucks and buses, where the challenges of charging infrastructure are even more pronounced. The core principles of system multiplexing and efficient power conversion could also inform the development of other energy conversion systems, contributing to broader efforts to improve energy efficiency and sustainability.
Conclusion: Paving the Way for a Seamless EV Future
As the electric vehicle market continues to grow and evolve, the need for interoperability between different generations of technology becomes increasingly important. The drive multiplexing boost technology developed by this research team represents a significant step toward addressing this need, offering a practical and cost-effective solution to the challenge of charging infrastructure compatibility.
By cleverly repurposing existing components and developing advanced control strategies, the researchers have demonstrated that it is possible to overcome the technical barriers to high-voltage EV adoption without waiting for widespread upgrades to charging infrastructure. This innovation not only benefits vehicle manufacturers and consumers but also supports the continued growth and sustainability of the broader electric mobility ecosystem.
As the automotive industry moves toward higher voltage architectures, solutions like this will play a crucial role in ensuring a smooth and efficient transition. The ongoing development and refinement of such technologies promise to make electric vehicles more accessible, more efficient, and more convenient, ultimately accelerating the global shift toward sustainable transportation.
This research was conducted by Hou Wenbo, Yang Ping, Chen Ke, Qu Bo, and Wu Wenrong from the School of Electrical Engineering at Southwest Jiaotong University in Chengdu and the Department of Power Consumption and Energy Efficiency at China Electric Power Research Institute in Beijing. Their findings were published in the “Transactions of China Electrotechnical Society” (Vol. 39, Supp. 1, December 2024) with the DOI: 10.19595/j.cnki.1000-6753.tces.L11033.