Porsche Engineering has introduced a groundbreaking concept in the world of electric vehicles – the ‘AC battery’. This innovative system combines multiple components into a single part, controlled by a standardized control unit concept with a powerful computing platform. The development of the AC battery was part of a feasibility study, where it was tested on a test bench and demonstrated in a vehicle.
Traditionally, the drive system in electric vehicles consists of separate components such as a high-voltage battery with a battery management system, power electronics for motor control, and an on-board charger for AC power charging. Porsche Engineering recognized the potential for improvement in integrating these components into a single unit. Thomas Wenka, Specialist Project Manager at Porsche Engineering, highlighted the advantages of highly integrated components, including size reduction, weight reduction, cost savings, improved reliability, and efficiency.
The AC battery system developed by Porsche Engineering integrates functions of the battery management system, pulse inverter, low-voltage DCDC, and on-board charger into a single component. The high-voltage battery is divided into 18 individual battery modules, controlled by power semiconductor switches. These modules are interconnected into a Modular Multilevel Series Parallel Converter (MMSPC), enabling dynamic modeling of the voltage curve to generate sinusoidal three-phase AC voltage for the motor directly from the battery modules.
The AC battery concept offers numerous technical advantages, including easier scalability, increased safety during servicing or accidents, failure protection in case of battery cell defects, and a limp-home function for reduced power to reach the nearest workshop. The system also has the potential for fast charging capabilities through pulsed charging.
One of the major challenges in implementing the AC battery concept was developing a powerful and fast central control unit to precisely control the individual battery modules. Porsche Engineering developed a control unit with a highly integrated computing platform consisting of a project-specific baseboard and a system-on-module with a uniform interface. This platform combines a field-programmable gate array (FPGA) for real-time control and monitoring with a powerful multicore processor for data processing.
The software-focused implementation of the control unit functions allows for dynamic reconfiguration through software, ensuring hard real-time capability that cannot be achieved with normal microcontrollers. The new control unit platform has been successfully tested in various prototypes and integrated into a test vehicle to demonstrate its functionality.
Looking ahead, Porsche Engineering plans to use the new control unit platform for prototype development, with potential for series applications with minor modifications. The flexibility of the platform allows for easy adaptation to new requirements, making it a valuable tool for projects where high computing power and real-time capability are essential. The integration of the AC battery concept and the new control unit platform represent a significant step forward in the evolution of electric vehicle technology.
