Understanding the small-signal stability of low-voltage DC microgrid

This paper aims to present novel insight into the small-signal stability of DC microgrid (MG) and improve the interpretability of instability phenomena. For this purpose, a fundamental DC MG has been developed. The boost converter operates as a source converter, supplying power through the DC cable to the buck converter, which is regulated by voltage and current controllers functioning as a constant power load. The DC cable and converter’s input filter dynamic are captured in the full-order model. Parameter sensitivity evaluation highlights the potential adverse effects of control interference and improper system parameter design. The analysis shows that a relative large boost converter inductance, small DC bus capacitance, large cable inductance, and heavy constant power load can cause the system’s dominant eigenvalues to shift to the right half of the complex plane, leading to instability. Besides, the controller parameters should be well tunned to avoid control interference. Time-domain simulations validate the parameter sensitivity analysis by illustrating the oscillation waveforms under poor parameter design conditions.