A Two-Step Stability Assessment Method for Interconnection of DC Distribution Networks

Interconnection of DC distribution networks is raising concerns over their stability. With the increasing number of power electronics converters, the conventional stability assessment methods require detailed internal information of the converters and passive network and/or large storage and computing power. In this paper, to fully protect the highest level of trade secret and user privacy and to avoid the curse of dimensionality, an improved pre-processing method is first developed to deal with the distribution networks prior to their interconnection. Then, a two-step stability assessment method is formulated to analyze the stability of the anticipated distribution networks subsequent to their interconnection. By comparing with the existing methods, the proposed one simultaneously achieves three objectives: i) it regards both the converters and passive network as black boxes and assesses the stability of the interconnected network solely based on the measured impedance/admittance; ii) it assesses system stability with a reduced-order system minor-loop gain and therefore, overcomes some of the difficulties of dimensionality curse; and iii) it prevents from the internal instability and guarantees the global stability of the interconnected distribution network. Finally, a modified IEEE 37-bus DC distribution network is implemented in the Matlab/Simulink environment to verify the validity of the proposed method.