Multiplexing Booster Technology for Electric Vehicle Drive
Hou Wenbo1, Yang Ping1, Chen Ke1, Qu Bo2, Wu Wenrong1
1. School of Electrical Engineering Southwest Jiaotong University Chengdu 611756 China; 2. Department of Power Consumption and Energy Efficiency China Electric Power Research Institute Co. Ltd Beijing 100192 China
Abstract：Electric vehicles (EVs) are rapidly adopting 800 V high-voltage architectures to improve their performance, increase charging rates, and enhance overall efficiency. This shift promises significant benefits, such as shorter charging times, improved energy efficiency, and better compatibility with future fast-charging infrastructure. However, the deployment of charging infrastructure that can support 800V systems is currently limited due to high costs, stringent distribution network requirements, and slow adoption. Currently, most DC charging piles in use are based on a 400 V low-voltage platform, which creates a challenge for the widespread adoption of 800 V EVs. As a result, a critical issue that needs to be addressed is how to make the high-voltage architecture of electric vehicles compatible with the existing low-voltage charging piles during this transitional period and in the future. To address this compatibility challenge, this study proposes a novel time-sharing multiplexing step-up charging topology and control strategy designed for electric vehicles. This strategy takes advantage of the fact that the drive system and the charging device do not operate simultaneously. When the vehicle is in charging mode, the motor winding is used as an energy storage inductor, and the motor inverter controller is repurposed as the chopper switch controller. Through a three-phase staggered parallel Boost circuit, the system achieves high-power boost conversion, making it possible to charge 800 V EVs from 400 V charging piles. This innovative approach improves compatibility with existing infrastructure while saving vehicle space, reducing weight, and lowering costs. Additionally, it increases the utilization rate of existing automotive components and public facilities, offering significant economic benefits and practical application value. The first step in this research involved analyzing the 800V high-voltage architecture and its charging requirements, followed by an investigation of the transient characteristics of the converter. The coupling relationships and the equivalent structure of the embedded permanent magnet synchronous motor winding were studied. Mathematical modeling and coordinate transformation techniques were used to determine the inductance values of the three-phase windings, and the influence of rotor position on the inductance was quantified. To further optimize the system, external inductance was introduced to eliminate the effects of mutual inductance. The state-space averaging method was applied to analyze both the DC steady-state and AC small-signal characteristics of the converter, providing a solid theoretical foundation for the design of the control loop. In terms of control strategy, the operating principles, advantages, and limitations of traditional voltage-current double-loop control and model predictive control (MPC) strategies were thoroughly analyzed. Given the unique characteristics of the equivalent inductance values of the three-phase windings in the multiplex boost converter motor, the research sought to improve the system's dynamic response speed while simplifying the design process. To achieve this, a hybrid control strategy combining PI (proportional-integral) control with MPC was proposed. The hybrid control retains the voltage loop PI regulator and incorporates an active current-sharing strategy. This PI-MPC hybrid control strategy enhances the system's dynamic response, especially in scenarios involving sudden load changes. The effectiveness of the proposed control strategies was verified through simulation. Both the traditional dual-loop control and the PI-MPC hybrid control strategy demonstrated excellent performance, achieving zero-error output voltage, balanced three-phase currents, and input combined current ripple below ±10A in steady-state operation across various rotor positions. Additionally, the PI-MPC hybrid control strategy showed superior dynamic response compared to traditional dual-loop control, especially under sudden load changes, further proving its effectiveness. To validate the theoretical findings, a 50 kW experimental platform was built in the Powertrain laboratory. The experiment involved a 250 V to 400 V boost conversion and the results were consistent with the simulations, verifying the accuracy of the proposed topology and control strategy. Overall, the study demonstrated that the designed drive multiplexing boost converter can reliably and stably achieve voltage boost through the integration of the vehicle’s drive system. This successfully addresses the challenge of making high-voltage architectures compatible with existing low-voltage charging piles, ensuring smooth and efficient operation during this crucial transition period for electric vehicle infrastructure.
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2024, Vol. 39 
