Bidirectional Energy Transfer for Heterogeneous Modular Batteries in Electric Vehicle Applications
Modular multilevel converters enable serial and bypass operation, which are suitable for using lower-voltage components in higher-voltage systems. Reconfigurable batteries capable of parallel connection take advantage of sensorless voltage balancing, battery saving, current sharing, and improved efficiency. However, the parallel connectivity does not allow any voltage difference between the modules or necessitates large inductors. This paper proposes modular reconfigurable batteries with inter-module differential chokes to allow controlled and efficient energy transfer across modules with arbitrary voltage differences and minimum impact on the output voltage. The output current operates as a common-mode current in the differential choke, neutralizing the magnetization effects of choke inductances and preventing saturation. This results in a differential choke inductor with a small core size. This study also offers a modulation strategy for controlling the differential current responsible for energy transfer among modules. The operational principle is discussed in detail and validated by simulations.
