Reduced RLC Impedance Circuit Model of Electric Vehicle DC Charging Station

  Introduction  The potential positive feedback of virtual inertia and damping control (VIDC) may exacerbate the interaction within the control loop, causing low-frequency oscillation of bus voltage and disrupting the stability of electric vehicle DC charging station (EVCS). Although the existing multi-timescale impedance model explains the stability mechanism of VIDC and the low-frequency oscillation mechanism of VIDC-controlled-EVCS, it is essentially a high-order transfer function, making it difficult to obtain analytical expressions for damping control strategies.

  Method  Therefore, a detailed impedance analysis of the virtual impedance of the loop was conducted to intuitively reveal the fundamental reasons for the higher-order properties of each loop impedance.

  Result  A closed-loop gain fitting method for the control loop was proposed through Bode diagram approximation, and a low-order impedance circuit model was established.

  Conclusion  The effectiveness of the proposed multi-timescale impedance model is verified through Matlab/Simulation.