Online Battery Impedance Spectroscopy Using Pseudo-Random Binary Sequence
Term
3. term
Education
Publication year
2025
Submitted on
2025-12-17
Pages
52
Abstract
Nowadays, electric vehicles (EVs) are becoming increasingly widespread. Consequently, there is a growing desire to obtain a better understand of their batteries both with respect to degradation and remaining capacity. Therefore, the aim of this project is to obtain the Nyquist plot of a battery while it is running a Permanent Magnet Synchronous Machine (PMSM) using an inverter. It is investigated whether a Pseudo-Random Binary Sequence (PRBS) could be a possible solution for this, since it produces a broad span of frequencies with the same magnitude, similar to Electrochemical Impedance Spectroscopy (EIS), without having to implement any costly hardware. For this purpose, a model containing a battery, inverter and PMSM with Field Oriented Control (FOC) is constructed, where the PRBS is applied in the d-current reference for minimal impact on the speed. In simulation environment, it was concluded that implementing PRBS is possible, however the method is sensitive to disturbances. Experimental validation was performed, using both 4-bit and 11-bit PRBS, where the method was approved. PRBS was applied to the motor under both stationary and operating conditions, resulting in a similar accuracy in Nyquist plot for operating case despite of the influence of the q-current. Additionally, only part of the Nyquist plot was obtained, due to the inherent nature of the PRBS frequency content. Nevertheless, it was concluded that PRBS can be used for the purpose of obtaining the Nyquist plot of a battery, although with limitations.
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