Impedance Modeling of Communication-Network-Embedded DC Microgrid

Abstract

Impedance model plays an important role in stability analysis of DC microgrids (MGs) with intuitiveness and effectiveness, especially when the state-space models with detailed system parameters are unavailable. Generally, impedance model can be evaluated at a particular port by system partitioning. However, in hierarchically-controlled DC MGs where distributed generators (DGs) are connected with communication links, it is difficult to split the DC MG into subsystems and derive the port impedance models. In this respect, a communication-network-embedded impedance model is proposed for DC MGs that contain distributed communication networks. Compared to state-of-the-art impedance models, the proposed method retains both local controller and distributed communication dynamics with a non-diagonal apparatus impedance matrix. Based on the proposed communication-network-embedded impedance model, the impedance participation analysis is extended to a distributed system with communication links. The theoretical analysis has been illustrated with a DC-powered trolleybus system as a modified 9-bus communication-network-embedded DC MG, an MMC-based multi-terminal DC grid, as well as a larger 20-bus hybrid AC/DC microgrid. Numerical calculations and time-domain simulations are performed to validate the theoretical analysis.