A Band-specific Virtual Impedance Strategy Based on Butterworth Filter

The fundamental configuration of the DC bus microgrid system is that of cascaded converters. Nevertheless, impedance interactions between converters may result in instability within the cascaded system. To mitigated this issue, this paper proposes a virtual impedance strategy based on Butterworth filter, which is capable of achieving impedance reconstruction within specific frequency bands. Firstly, a DC microgrid system is modelled with impedance to derive the impedance characteristics. The impedance characteristics of the strategy with a single proportional voltage feedforward, the virtual impedance strategy based on the conventional second-order bandpass filter and proposed strategy are compared. Results demonstrate that the proposed strategy exhibits superior improvement in a specific frequency band with minimal out-of-band effects. Finally, a modeling and hardware experimental setup have been established to validate its effectiveness.