μ approach to robust stability domains in the space of parametric uncertainties for a power system with ideal CPL

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 method has proven to be a reliable approach for assessing the stability robustness of such uncertain systems. Despite its numerous benefits, the method is not often applied to electrical power systems (EPS) with multiple uncertainties. This may be due to the mathematical complexity underlying the theory. This work aims to make the approach more application-friendly by providing clearer insights into the meaning and usefulness of the robust stability measure for EPS with multiple parametric uncertainties. This is achieved by presenting a methodology for translating 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. analysis predictions are evaluated and validated against analytical results for the example CPL system

Robust stability analysis of power electronic systems

Power electronics is the enabling technology that can put transportation on a more sustainable pathway. The key problem with power electronic (PE) systems is that they are prone to instability. Classical techniques are insufficient at assessing the stability of these systems, as they do not take into account the uncertain nature of physical systems. This thesis presents the structured singular value (SSV) method as an effective, reliable and robust stability analysis approach that justifiably incorporates uncertainties which are inherently present in physical systems. Although the SSV approach has numerous benefits, it has a few drawbacks that tend to make it hard to apply. Its theoretical framework remains complex. The practical approaches to applying the SSV method to PE systems seem lacking in the literature. The SSV approach is generally applied to linear system models while most systems are non-linear in nature. This thesis demonstrates the applicability of the SSV method to PE systems, by addressing these limitations. The work first brings deeper and clearer insights into key concepts of SSV theory. It demonstrates the significance and usefulness of the robust stability measure (SSV) in the space of multiple parametric uncertainties, through the concept of the hypercube. Secondly, it presents several practical approaches to applying the SSV method to PE systems. Finally, it develops a modelling methodology that converts a non-linear system to an equivalent linear model, suited for SSV analysis. The findings are supported by simulation and experimental results of the buck converter, permanent magnet machine drive, ideal constant power load and resistance-inductance-capacitance systems. This thesis provides the design engineer with some crucial theoretical and practical tools for applying the SSV approach to both linear and non-linear models of PE systems, while showing how to reap the full benefits of the method. It is the author's belief that the SSV method can be used as widely as classical methods, and to great effect

Robust stability analysis of a dc/dc buck converter under multiple parametric uncertainties

Stability studies are a crucial part of the design of power electronic systems, especially for safety critical ap¬plications. 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 method justifiably takes into account all possible uncertainties in the system. However, the application of the method to power electronic systems with multiple uncertainties is not widely discussed in the literature. This work presents practical approaches to applying the 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 predictions are supported by time domain simulation and experimental results

Finite state machine control for aircraft electrical distribution system

This study deals with the development of new control logic for more electric aircraft (MEA) electrical power systems (EPSs). A key aspect of the MEA concept is that traditional pneumatic and hydraulic loads are replaced by electrical equivalents. These new electrical systems are more reliable, highly efficient, and easier to replace or maintain. However, as the number of on-board electrical loads increases the electrical distribution systems on-board are becoming more and more complex. As a result, the control system needs to be adapted and improved in order to allow better manage the overall electrical energy flow, provide faster computational operations, and ensure operation of safety-critical loads under all fault scenarios. This study first gives a brief analysis of the different electrical system topologies before outlining potential control strategies which may be applicable to future MEA EPSs. A new control concept for MEA EPSs is then investigated and considered as a potential substitute of the classical control systems. Finally, a model of the newly proposed logic is implemented and simulated showing how it is able to select and apply a correct reconfiguration of the electrical system under different operating conditions

ENIGMA—A Centralised Supervisory Controller for Enhanced Onboard Electrical Energy Management with Model in the Loop Demonstration

A centralised smart supervisor (CSS) controller with enhanced electrical energy management (E2-EM) capability has been developed for an Iron Bird Electrical Power Generation and Distribution System (EPGDS) within the Clean Sky 2 ENhanced electrical energy MAnagement (ENIGMA) project. The E2-EM strategy considers the potential for eliminating the 5 min overload capability of the generators to achieve a substantial reduction in the mass of the EPGDS. It ensures optimal power and energy sharing within the EPGDS by interfacing the CSS with the smart grid network (SGN), the energy storage and regeneration system (ESRS), and the programmable load bank 1 secondary distribution board (PLB1 SDU) during power overloads and failure conditions. The CSS has been developed by formalizing E2-EM logic as an algorithm operating in real time and by following safety and reliability rules. The CSS undergoes initial verification using model-in-the-loop (MIL) testing. This paper describes the EPGDS simulated for the MIL testing and details the E2-EM strategy, the algorithms, and logic developed for the ENIGMA CSS design. The CSS was subjected to two test cases using MIL demonstration, and based on the test results, the performance of the ENIGMA CSS is verified and validated

Robust stability analysis of power electronic systems

Power electronics is the enabling technology that can put transportation on a more sustainable pathway. The key problem with power electronic (PE) systems is that they are prone to instability. Classical techniques are insufficient at assessing the stability of these systems, as they do not take into account the uncertain nature of physical systems. This thesis presents the structured singular value (SSV) method as an effective, reliable and robust stability analysis approach that justifiably incorporates uncertainties which are inherently present in physical systems. Although the SSV approach has numerous benefits, it has a few drawbacks that tend to make it hard to apply. Its theoretical framework remains complex. The practical approaches to applying the SSV method to PE systems seem lacking in the literature. The SSV approach is generally applied to linear system models while most systems are non-linear in nature. This thesis demonstrates the applicability of the SSV method to PE systems, by addressing these limitations. The work first brings deeper and clearer insights into key concepts of SSV theory. It demonstrates the significance and usefulness of the robust stability measure (SSV) in the space of multiple parametric uncertainties, through the concept of the hypercube. Secondly, it presents several practical approaches to applying the SSV method to PE systems. Finally, it develops a modelling methodology that converts a non-linear system to an equivalent linear model, suited for SSV analysis. The findings are supported by simulation and experimental results of the buck converter, permanent magnet machine drive, ideal constant power load and resistance-inductance-capacitance systems. This thesis provides the design engineer with some crucial theoretical and practical tools for applying the SSV approach to both linear and non-linear models of PE systems, while showing how to reap the full benefits of the method. It is the author's belief that the SSV method can be used as widely as classical methods, and to great effect