Effect of CPL on the Stability of DC Microgrid

This paper presents a comprehensive dynamic analysis of a DC microgrid operated with constant power loads (CPL). The DC microgrids are gaining immense attention due to many technical and economical advantages over AC microgrids. However, the DC microgrids operation is highly sensitive to CPLs, due to their negative impedance characteristics. This negative impedance characteristics of CPL reduces the system damping and causes destabilizing effect by moving one or more poles to right half of s-plane. Initially, the effect of CPL is analyzed on a single DC-DC boost converter connected to CPL by observing the poles of the control to output transfer function model. Later, these impacts on complete DC microgrid system is studied by developing a small signal model using jacobian linearization of the dynamic equations. The influence of droop gain and linear loads in the presence of CPL on DC microgrid are analyzed using the developed small signal model eigen value traces. These eigen value responses are also validated through non-linear system simulation preformed in MATLAB/Simulink platform.