Robustness analysis of large power systems with parametric uncertainties

IEEE Trans. Power Electron.

2018

Sumsurooah, Sharmila and Odavic, Milijana and Bozhko, Serhiy (2017) A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription.For more information, please contact eprints@nottingham.ac.uk µ approach to robust stability domains in the space of parametric uncertainties for a power system with ideal CPL Sharmila Sumsurooah, Milijana Odavic, Member, IEEE, and Serhiy Bozhko, Member, IEEE Abstract-Power electronic systems are prone to instability. The problem, generally attributed to the constant power load (CPL) behaviour of their power electronic controlled loads, can become more acute when the systems are subject to parametric uncertainties. The structured singular value (SSV) based µ method has proven to be a reliable approach for assessing the stability robustness of such uncertain systems. Despite its numerous benefits, the µ method is not often applied to electrical power systems (EPS) with multiple uncertainties. This may be due to the mathematical complexity underlying the µ theory. This work aims to make the µ approach more application-friendly by providing clearer insights into the meaning and usefulness of the robust stability measure µ for EPS with multiple parametric uncertainties. This is achieved by presenting a methodology for translating µ analysis results from the frequency domain to the more perceivable uncertain parameters domain. The method directly demonstrates dependences of system stability on uncertain system parameters. Further, it clearly identifies robust stability domains as subsets of the much wider stability domains. The work is based on a representative EPS connected to an ideal CPL. µ analysis predictions are evaluated and validated against analytical results for the example CPL system.

Section: Analytical Assessment Of System Stabilitymentioning

confidence: 99%

Section: B Analytical Verificationmentioning

confidence: 99%

See 1 more Smart Citation

$\mu$ Approach to Robust Stability Domains in the Space of Parametric Uncertainties for a Power System With Ideal CPL

IEEE Trans. Power Electron.

2018

“…As a result, the initial state-space matrix is expanded to accommodate two sets of inputs namely u ∆ and u s and two sets of output y ∆ and y s , as shown in Fig. 3 [11], [18]. The expanded state-space matrix can be simplified by absorbing the "states" through the use of (2)- (5).…”

Section: A Linear Fractional Transformationmentioning

confidence: 99%

A Modeling Methodology for Robust Stability Analysis of Nonlinear Electrical Power Systems Under Parameter Uncertainties

IEEE Trans. on Ind. Applicat.

2016

Abstract-This paper develops a modeling method for robust stability analysis of nonlinear electrical power systems over a range of operating points and under parameter uncertainties. Standard methods can guarantee stability under nominal conditions, but do not take into account any uncertainties of the model. In this study, stability is assessed by using structured singular value (SSV) analysis, also known as µ analysis. This method provides a measure of stability robustness of linear systems against all considered sources of structured uncertainties. The aim of this study is to apply the SSV method for robust small-signal analysis of nonlinear systems over a range of operating points and parameter variations. To that end, a modeling methodology is developed to represent any such system with an equivalent linear model that contains all system variability, in addition to being suitable for µ analysis. The method employs symbolic linearization around an arbitrary operating point. Furthermore, in order to reduce conservativeness in the stability assessment of the nonlinear system, the approach takes into account dependences of operating points on parameter variations. The methodology is verified through µ analysis of the equivalent linear model of a 4-kW permanent magnet machine drive, which successfully predicts the destabilizing torque over a range of different operating points and under parameter variations. Further, the predictions from µ analysis are validated against experimental results.Index Terms-Linear fractional transformation (LFT), µ analysis, robust stability analysis, structured singular value (SSV).

“…In addition, the µ method is generally applied to linear systems while most systems analysed have nonlinear behaviour. A few works in the literature have successfully applied the µ method to analyse stability of conventional power systems [33], [34], [35], [36], [37], [38]. However, the methodology applied through associated software is not discussed and multiple uncertainties are not considered.…”

Section: Introductionmentioning

confidence: 99%

Robust Stability Analysis of a DC/DC Buck Converter Under Multiple Parametric Uncertainties

IEEE Trans. Power Electron.

et al. 2018

Abstract-Stability studies are a crucial part of the design of power electronic systems, especially for safety critical applications. Standard methods can guarantee stability under nominal conditions but do not take into account the multiple uncertainties that are inherent in the physical system or in the system model. These uncertainties, if unaccounted for, may lead to highly optimistic or even erroneous stability margins. The structured singular value-based µ method justifiably takes into account all possible uncertainties in the system. However, the application of the µ method to power electronic systems with multiple uncertainties is not widely discussed in the literature. This work presents practical approaches to applying the µ method in the robust stability analysis of such uncertain systems. Further, it reveals the significant impact of various types of parametric uncertainties on the reliability of stability assessments of power electronic systems. This is achieved by examining the robust stability margin of the dc/dc buck converter system, when it is subject to variations in system load, line resistance, operating temperature and uncertainties in the system model. The µ predictions are supported by time domain simulation and experimental results.Index Terms-Robust stability analysis, dc/dc buck power electronic converter, Linear fractional transformation, Structured singular value, µ analysis.