Stability Analysis of Electric Vehicle DC Bus Based on Middlebrook Impedance Criterion

To enhance the stability of the electrical system in electric vehicles, this paper adopts a small-signal analysis method based on impedance modeling to analyze and model the DC microgrid system consisting of power electronics-based sources, networks, loads, and energy storage devices in electric vehicles. Utilizing the Middlebrook impedance-ratio stability criterion, combined with system simplification, linearization of nonlinear systems, and transformation of three-phase AC systems, small-signal output impedance models of the DC bus and input impedance models of the inverter and motor are established. Furthermore, a simulation model of the DC propulsion system is developed to investigate the impacts of the support capacitor, equivalent resistance, and equivalent inductance of the DC bus on system stability. Simulation results demonstrate that the impedance matching between the source and load sides effectively reveals the stability patterns and underlying mechanisms under various operating conditions and parameter variations, providing theoretical guidance and a solid foundation for optimizing the DC bus system parameters.