Robust Stability Analysis of DC Microgrids With Constant Power Loads

Abstract

Abstract-This paper studies stability analysis of DC microgrids with uncertain constant power loads (CPLs). It is well known that CPLs have negative impedance effects, which may cause instability in a DC microgrid. Existing works often study the stability around a given equilibrium based on some nominal values of CPLs. However, in real applications, the equilibrium of a DC microgrid depends on the loading condition that often changes over time. Different from many previous results, this paper develops a framework that can analyze the DC microgrid stability for a given range of CPLs. The problem is formulated as a robust stability problem of a polytopic uncertain linear system. By exploiting the structure of the problem, we derive a set of sufficient conditions that can guarantee robust stability. The conditions can be efficiently checked by solving a convex optimization problem whose complexity does not grow with the number of buses in the microgrid. The effectiveness and nonconservativeness of the proposed framework are demonstrated using simulation examples.

Distributed Nonlinear Control With Event-Triggered Communication to Achieve Current-Sharing and Voltage Regulation in DC Microgrids

“…25 in Appendix, the block matrices in LW can be written as: . In this sense, the main Kron reduction process [26] from (5) to (7) is shown in Fig. 2.…”

“…In a typical dc MG, constant power loads (CPLs) need to be carefully considered, which can undermine the stability and damping of the system. Traditionally, V-I droop controller can provide active damping of the oscillations [5], [28] by the virtual resistance. However, the proposed controller replaces V-I droop controller.…”

“…Under the paradigm of distributed generation and consumption, a robust and flexible control scheme is always preferred, while the challenges still exist on distributed information sharing, global stable and system coordination. In dc MGs, since there is no reactive power [3], transformer inrush current, or harmonics, higher Manuscript received February 17, 2017; revised May 28, 2017 and July 25, 2017; accepted August 31, 2017. power quality and system efficiency can be obtained comparing to ac MGs [4], [5]. Naturally, it is a more efficient method to connect the sources and loads directly to form a dc MG by using dc-dc converters without ac-dc or dc-ac transformations.…”

New Analysis Framework for Transient Stability Evaluation of DC Microgrids

“…Based on this simplified model, the semidefinite programming technology is used to evaluate the ROA of the system. Liu et al [13] pay attention to the robust stability of dc microgrids considering the uncertainty of CPLs. In [14] and [15], the transient (or large-signal) stability analysis tools in microgrids are summarized.…”

Primary and secondary control in DC microgrids: a review

“…The rapid development of power electronics technology has allowed the converters to operate at a wide range of DC voltage levels, including transmission, distribution and consumption level. Compared to AC MGs [3,4], the advantages of DC MGs can be summarized as follows [5]: 1) Most renewable energy resources, such as photovoltaic (PV) panels and fuel cells produce DC power. Even wind turbines, which intrinsically produce AC power, can be more conveniently integrated into a DC grid due to the absence of more power conversions.…”