Dynamic Improvement of DC Microgrids with CPLs Using Virtual Inertia Concept

In this paper, a virtual inertia control strategy based on linear feedback is presented that improves dynamic behavior of islanded dc microgrids interfaced with constant power loads (CPLs). In order to solve the stability challenges caused by low inertia and CPLs, the proposed control scheme is composed of a virtual capacitor and a virtual conductance. It is implemented in the inner loop control, i.e. current loop control to be fast enough emulating inertia and damping concept. In addition, the droop characteristic is modeled by using the virtual resistance which adjusts the steady-state response of the system. In this study a multi-level structure is considered, which comprises the source level, interface converter level, and common load level. In addition, an accurate small-signal model is used to investigate the stability of dc MG interlaced with CPLs, and then, an acceptable range of inertia response parameters is determined by using the root locus analysis. Performance of the proposed control structure is demonstrated through numerical simulations