The stability of dc power electronics based power distribution systems, and in particular dc systems, is a significant design consideration because of the potential for negative impedance induced instabilities. In this paper, methodologies for analyzing the stability of these systems are reviewed.
In particular, tools including timedomain simulation, generalized immittance analysis, and polytopic analysis are considered. The use of both time-domain simulation and generalized immittance analysis for a three-zone hardware test system, the Naval Combat Survivability DC Distribution Testbed, is set forth.
The predictions of both of these methods are shown to be in agreement with the observed behavior of the system. Polytopic analysis is then considered as a possible future tool for exploring stability properties. The results of each of these analyses as well as the respective advantages and disadvantages of each of the methods are compared.
One of the defining characteristics of power electronics based systems is that they facilitate a high degree of automation and nearly instantaneous reconfiguration capabilities.
Many power converters also feature nearly perfect regulation of their output objectives. From the output perspective, this property is highly desirable. However, it has unfortunate consequences. In particular, since power electronic converters are very efficient, ideal regulation of the output makes the converter appear as a constant power load from its input side.
As such, an increase in input voltage will cause a decrease in input current — and hence the incremental input resistance to such a converter is negative. Negative incremental input resistance is destabilizing — and can result in instability of the interconnected power system.
As a result, the stability analysis of such systems is of paramount importance.
In this paper, different methods of analyzing the stability of power electronics based power distribution systems are reviewed and applied to the Naval Combat Survivability DC Distribution System , , . This hardware testbed consists of ten power converters in a zonal architecture often considered for future Navy ships.
Methods of stability analysis are discussed, with special emphasis on time-domain simulation, generalized immittance analysis, and the direct method of Lyapunov. The predictions of the time-domain simulation and the generalized immittance analysis are compared with experimentally measured results.
In particular, these two methods are shown to predict the stability or lack thereof of the hardware test system. This is the first time the generalized immittance analysis approach has been validated in hardware on a system wide basis.
The paper concludes with a discussion of future directions of stability analysis of power electronics based systems using nonlinear methods with emphasis on the use of polytopic modeling techniques. Definitions for these concepts are readily applied to a mathematical model of a system, but are not as readily applied to the system itself since the notion of state variables breaks down when discussing physical systems.
Furthermore, even in the case of the mathematical model of a power electronics based system, the state variables in a model detailed enough to portray the switching action of the power semiconductors will never become constant. Thus when defining terms related to stability it is necessary to differentiate those definitions as applied to a system model from those as applied to the system.
Herein, when referring to a mathematical model, an equilibrium point is a point at which the derivatives of the state variables are zero.
In the case of a model in which switching is represented, the equilibrium point is a point at which the fast or dynamic average of the derivatives of the state variables are zero .
An operating point is defined as an equilibrium point about which the system is being studied.
|Stability Analysis Methodologies for DC Power Distribution Systems | timberdesignmag.com||Institutt for elkraftteknikk  Abstract The recent advancements in power electronics have resulted in widespread use of electronically controlled energy sources and loads in both AC and DC distribution systems. Power electronics also plays an important role in the emerging and future transportation systems like electric vehicles, electric ships, and more electric aircraft.|
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|Modeling, Control and Stability Analysis of a PEBB Based DC Distribution Power System||Power and Energy Systems Stability of Power Electronics Based Power Distribution Systems Power electronics based power distribution systems are becoming increasingly prevalent in ships, aircraft, and spacecraft, and have elements which are appearing on the bulk power grid.|
If conditions are such that there is only one possible equilibrium point then these terms become synonymous. An operating point of the system model is said to be locally stable if, when perturbed from an operating point by a small amount, the system model returns to that operating point.
An operating point of the system model is said to be globally stable if the operating point can be perturbed by any amount and still return to that operating point. In regard to the physical system as opposed to a mathematical modelan operating point is defined to be the fast average of the voltages and currents that would satisfy power flow requirements for some loading condition.
A dc power system is said to be locally stable about an operating point if the system voltages and currents vary only at the forcing frequencies associated with the switching of the power semiconductors and that the average values of these variables is such that all power converters are operating properly.
In other words, the system is said to be stable if, neglecting switching induced ripple, the voltages and currents are constant in the steadystate and the level of these voltages and currents is such that all converters are operating in their intended modes of operation.
Although this definition is admittedly informal and imprecise, it is nevertheless useful — particularly when we are discussing the stability of the system and not a model of the system. These comments with regard to stability are intended for informal discussion only.
For a thorough and rigorous discussion, the reader is referred to  and . This reduced-scale hardware test bed was developed by the Navy and the Energy Systems Analysis Consortium ESACa consortium of universities  in order to serve as a resource for researchers in Naval power and propulsion systems.
It is intended to play a role analogous to the IEEE test systems for the electric utility grid. In this system, there are two power supplies PS1 and PS2one of which feeds the port bus, and the other of which feeds the starboard bus only one connection is active at a time.
There are three zones of dc distribution. Diodes prevent a fault from one bus being fed by the opposite bus.
The converter modules feature a droop characteristic so that they share power. Robustness in this system is achieved as follows.Abstract. In recent times dc distribution system is become a very complex which consist different types of multiple power converters.
But system is suffered from stability related problem which arise due to negative incremental impedance of constant power loads. While  sets forth the basic methodology of immittance based stability analysis in the context of a source load system, it is extended in  to the analysis of entire distribution systems in a systematic way.
This paper presents the complete stability analysis of a dc distribution system composed of power electronics-based source and load. For this objective, a discrete-time dynamic model is developed and is applied to the studied system.
Modeling, Control and Stability Analysis of a PEBB Based DC Distribution Power System by Gurjit Singh Thandi Thesis submitted to the Faculty of the. The stability of dc power electronics based power distribution systems, and in particular dc systems, is a significant design consideration because of the potential for negative impedance induced instabilities.
A Mathematical Model for Stability Analysis of a DC Distribution System for Power System Integration of Plug-In Electric Vehicles Abstract: This paper proposes a systematic method for developing a model of a dc distribution system, based on the configuration of the system.