A review of power converter-based online electrochemical impedance spectroscopy for electrochemical devices in electric vehicles

Electrochemical Impedance Spectroscopy (EIS) serves as a critical non-destructive technique for characterizing electrochemical systems, including batteries, fuel cells, and supercapacitors. Its ability to extract frequency-domain impedance data enables effective assessment of key operational states such as State-of-Charge (SOC) and State-of-Health (SOH). However, the growing demand for real-time monitoring in dynamic operating conditions necessitates advancements in online EIS technology, which offers enhanced noise immunity and dynamic adaptability compared to conventional static EIS method. To address this requirement, the energy storage systems interfaced with power converters and equipped with online EIS functionality have emerged as a promising solution. This approach allows in-situ diagnostics at high power or pack levels without external instrumentation by utilizing existing energy conversion hardware. This article focuses on the research progress of power converter-based online EIS technology, identifying three fundamental conditions for its implementation. Multiple converter topologies are compared experimentally using switching frequency (>100 kHz switching enabling EIS diagnostics in the tens of kHz band) and EIS level as key metrics in various scenarios. Challenges associated with high-frequency EIS testing, particularly switching noise interference and excitation bandwidth, are discussed alongside solutions such as advanced filtering techniques and control methods. Finally, future research trends emphasize the development of the utilization of wide-bandgap semiconductor technologies for high-frequency excitation and AI-enhanced EIS diagnostics. The systematic analysis presented facilitates improved monitoring and management of electrochemical devices in real-time applications such as electric vehicles.