A Generic Small-Signal Stability Criterion of DC Distribution Power System: Bus Node Impedance Criterion (BNIC)

The dc distribution power system has drawn widespread attention and rapidly developed in recent years; however, its stability issue is one of the urgent challenges, requiring much attention. In previous stability studies, the line impedance network is often overlooked, which is convenient for the geographically centralized systems, but inaccurate for the distributed systems. In this article, the modeling and stability criteria of these two systems are simultaneously studied. For the distributed systems, first, the transfer functions from each input voltage or current disturbance to the bus voltage are derived. On this basis, the sufficient and necessary condition for the system stability is discussed. Subsequently, a bus node impedance criterion (BNIC) is proposed to assess the small-signal stability of the dc distribution power system. For the centralized systems, by ignoring the line impedance network, its small-signal model can be deduced by the distributed system, and the proposed BNIC is proved to be still valid. In addition, some existing impedance-based stability criteria are analyzed and compared with the proposed BNIC. Finally, the correctness and effectiveness of the proposed BNIC are verified by the cases study and experiments.

I. Introduction

With the high penetration of photovoltaic, wind power and energy storage systems [1]–[3], as well as the increase of dc loads [4], the dc distribution power system has been widely studied and developed. Nevertheless, due to the complex interaction between subsystems and the negative impedance characteristic of constant power load (CPL), the stability issue is still a big challenge [5]–[13], which is closely concerned by academia and industry.