A Reduced-Order Impedance Model and Analytical Loop-Correction Stabilization Method for Electric Vehicle DC Charging Station

Although impedance-based method has been proposed to effectively analyze interaction stability, the existing all-in-one impedance model-based method might encounter difficulty in identifying the physical significance of potential instability factors in the electric vehicle charging station and in solving the analytical solution of stabilization method aimed at entirely mitigating the voltage low-frequency oscillation (LFO) of each bandwidth due to its modeling complexity and high-order property. To address this issue, an analytical loop-correction stabilization method is designed based on the multi-timescale reduced-order impedance model to improve the dynamics of each bandwidth. Initially, the reduced-order expression of multi-timescale impedance model are presented by fitting the bode curve of closed voltage- and inertia-loop gain (G_vcl(s) and G_vir(s)). Subsequently, the analytical solution of loop-correction stabilization method can be designed and then performed to advance the phase and/or amplitude response of G_vcl(s) and G_vir(s). The negative damping within droop- and voltage-loop bandwidths is partly eliminated or completely offset, the LFO amplitude is suppressed and the LFO duration is shortened obviously due to the system stability enhancement and dynamic improvement. The voltage LFO of each timescale can be mitigated individually by the loop correction within each bandwidth. The bode-diagram-based solving process of this analytical loop-correction stabilization method is highly compatible for practical engineering applications. Finally, the effectiveness of proposed analytical loop-correction stabilization method is validated by physical experiment.