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This Special Issue of Energies, “Modern Power System Dynamics, Stability and Control”, addresses the core problem of deploying novel aspects in the analysis of modern power systems as these are composed after the high penetration of distributed generation (DG) with different renewable energy sources (RES). The focus is given either on the new whole power and control system configuration or on individual cases of DG sources, power converters and other general or specific plants and devices. The problem can be tackled with different methodologies and may have several, more or less valuable and complicated solutions. The twenty-three accepted papers certainly offer a good contribution in a wide range of applications; they are extended from basic system theory perspectives, fundamental nonlinear analysis tools and novel modeling deployments to some interesting particular system and control issues.
Antonio T. Alexandridis. Modern Power System Dynamics, Stability and Control. Energies 2020, 13, 3814 .
AMA StyleAntonio T. Alexandridis. Modern Power System Dynamics, Stability and Control. Energies. 2020; 13 (15):3814.
Chicago/Turabian StyleAntonio T. Alexandridis. 2020. "Modern Power System Dynamics, Stability and Control." Energies 13, no. 15: 3814.
Modern power systems are continuously transformed into decentralized ones where distributed generation (DG) plays a key role. Almost all the different distributed energy resources (DERs) are connected in geographically dispersed places through controlled power electronic interfaces in a manner that essentially affects the dynamic performance and control of the whole power system. Simultaneously, rotating machines in power production or absorption, dominate the system response and stability. In this new frame, this paper proposes a novel generalized dynamic representation and full scale modeling of a modern power system based on the well-known impedance-admittance (IA) network model for the electricity grid, substantially extended to include in detail both the power converter devices by considering the controlled power electronic dynamics and the electrical machines by inserting their full electromechanical dynamics. This formulation results in a holistic nonlinear dynamic description, defined here as controlled impedance-admittance-torque (CIAT) model of the whole system which features common structural characteristics. The model is deployed in state space, involves all the controlled inputs in DG, namely the duty-ratio signals of each power converter interface, all the other external inputs affecting the system, namely all the known or unknown voltage, current, and torque inputs. As shown in the paper, the proposed CIAT model retains its fundamental properties for any DG and network topology, standard or varying. This enables the compression of the accurate analytic power system dynamic description into a matrix-based generic nonlinear model that can be easily used for analysis studies of such large-scale systems. Taking into account the nonlinear nature of the CIAT matrix-based model and the persistent action of the external inputs, Lyapunov methods deployed on recently established input to state stability (ISS) notions are systematically applied for the system analysis. Hence, the traditionally used small-signal model-based analysis that suffers from the intermittent and continuously changing operation of DERs is completely substituted by the proposed formulation. A modern power system example with different DERs involved is analyzed by this way and is extensively simulated to verify the validity of the proposed method.
Panos C. Papageorgiou; Antonio T. Alexandridis. Controlled Impedance-Admittance-Torque Nonlinear Modeling and Analysis of Modern Power Systems. Energies 2020, 13, 2461 .
AMA StylePanos C. Papageorgiou, Antonio T. Alexandridis. Controlled Impedance-Admittance-Torque Nonlinear Modeling and Analysis of Modern Power Systems. Energies. 2020; 13 (10):2461.
Chicago/Turabian StylePanos C. Papageorgiou; Antonio T. Alexandridis. 2020. "Controlled Impedance-Admittance-Torque Nonlinear Modeling and Analysis of Modern Power Systems." Energies 13, no. 10: 2461.
A novel method of analysis is deployed in detail on the basis of nonlinear systems theory with aim to design suitable controllers with guaranteed stability for grid-connected photovoltaic (PV) systems driven by power converters. By this method, all the system nonlinearities are taken into account to allow a reliable analysis in a wide range of operation and to avoid instabilities that as shown in the paper can be occurred by inappropriate design. To this end, firstly a detailed accurate nonlinear dynamic model is presented for the PV system by including a cascade-mode control scheme. Then, taking into account the closed-loop system and incorporating the concept of input-to-state stability (ISS), a rigorous novel stability analysis is developed which achieves to prove asymptotic stability of the desired equilibrium point. A multi-step process is deployed in which the control loops operating in cascade-mode are involved. However, since the cascaded-mode control scheme and analysis is based on the time-scale separation principle, a systematic tuning method is conducted for the accurate gain selection of both innerloop and outer-loop controllers which is based on the construction of suitable Lyapunov functions. To further validate the overall analysis, experimental results are carried out.
Konstantinos F. Krommydas; Antonio T. Alexandridis. Nonlinear Analysis Methods Applied on Grid-Connected Photovoltaic Systems Driven by Power Electronic Converters. IEEE Journal of Emerging and Selected Topics in Power Electronics 2020, 8, 3293 -3306.
AMA StyleKonstantinos F. Krommydas, Antonio T. Alexandridis. Nonlinear Analysis Methods Applied on Grid-Connected Photovoltaic Systems Driven by Power Electronic Converters. IEEE Journal of Emerging and Selected Topics in Power Electronics. 2020; 8 (4):3293-3306.
Chicago/Turabian StyleKonstantinos F. Krommydas; Antonio T. Alexandridis. 2020. "Nonlinear Analysis Methods Applied on Grid-Connected Photovoltaic Systems Driven by Power Electronic Converters." IEEE Journal of Emerging and Selected Topics in Power Electronics 8, no. 4: 3293-3306.
The cyber–physical system (CPS) architecture provides a novel framework for analyzing and expanding research and innovation results that are essential in managing, controlling and operating complex, large scale, industrial systems under a holistic insight. Power systems constitute such characteristically large industrial structures. The main challenge in deploying a power system as a CPS lies on how to combine and incorporate multi-disciplinary, core, and advanced technologies into the specific for this case, social, environmental, economic and engineering aspects. In order to substantially contribute towards this target, in this paper, a specific CPS scheme that clearly describes how a dedicated cyber layer is deployed to manage and interact with comprehensive multiple physical layers, like those found in a large-scale modern power system architecture, is proposed. In particular, the measurement, communication, computation, control mechanisms, and tools installed at different hierarchical frames that are required to consider and modulate the social/environmental necessities, as well as the electricity market management, the regulation of the electric grid, and the power injection/absorption of the controlled main devices and distributed energy resources, are all incorporated in a common CPS framework. Furthermore, a methodology for investigating and analyzing the dynamics of different levels of the CPS architecture (including physical devices, electricity and communication networks to market, and environmental and social mechanisms) is provided together with the necessary modelling tools and assumptions made in order to close the loop between the physical and the cyber layers. An example of a real-world industrial micro-grid that describes the main aspects of the proposed CPS-based design for modern electricity grids is also presented at the end of the paper to further explain and visualize the proposed framework.
George C. Konstantopoulos; Antonio T. Alexandridis; Panos C. Papageorgiou. Towards the Integration of Modern Power Systems into a Cyber–Physical Framework. Energies 2020, 13, 2169 .
AMA StyleGeorge C. Konstantopoulos, Antonio T. Alexandridis, Panos C. Papageorgiou. Towards the Integration of Modern Power Systems into a Cyber–Physical Framework. Energies. 2020; 13 (9):2169.
Chicago/Turabian StyleGeorge C. Konstantopoulos; Antonio T. Alexandridis; Panos C. Papageorgiou. 2020. "Towards the Integration of Modern Power Systems into a Cyber–Physical Framework." Energies 13, no. 9: 2169.
In this paper, we present a nonlinear coordinated excitation and static var compensator (SVC) control for regulating the output voltage and improving the transient stability of a synchronous generator infinite bus (SGIB) power system. In the first stage, advanced nonlinear methods are applied to regulate the SVC susceptance in a manner that can potentially improve the overall transient performance and stability. However, as distant from the generator measurements are needed, time delays are expected in the control loop. This fact substantially complicates the whole design. Therefore, a novel design is proposed that uses backstepping methodologies and feedback linearization techniques suitably modified to take into account the delayed measurement feedback laws in order to implement both the excitation voltage and the SVC compensator input. A detailed and rigorous Lyapunov stability analysis reveals that if the time delays do not exceed some specific limits, then all closed-loop signals remain bounded and the frequency deviations are effectively regulated to approach zero. Applying this control scheme, output voltage changes occur after the large power angle deviations have been eliminated. The scheme is thus completed, in a second stage, by a soft-switching mechanism employed on a classical proportional integral (PI) PI voltage controller acting on the excitation loop when the frequency deviations tend to zero in order to smoothly recover the output voltage level at its nominal value. Detailed simulation studies verify the effectiveness of the proposed design approach.
Haris E. Psillakis; Antonio T. Alexandridis. Coordinated Excitation and Static Var Compensator Control with Delayed Feedback Measurements in SGIB Power Systems. Energies 2020, 13, 2181 .
AMA StyleHaris E. Psillakis, Antonio T. Alexandridis. Coordinated Excitation and Static Var Compensator Control with Delayed Feedback Measurements in SGIB Power Systems. Energies. 2020; 13 (9):2181.
Chicago/Turabian StyleHaris E. Psillakis; Antonio T. Alexandridis. 2020. "Coordinated Excitation and Static Var Compensator Control with Delayed Feedback Measurements in SGIB Power Systems." Energies 13, no. 9: 2181.
The integration of distributed energy resources (DERs) in modern power systems has substantially changed the local control capabilities of the grid since the majority of DERs are connected through a controlled dc/ac inverter interface. Such long-distance located DER installations, usually represented by current regulated dc sources, can inject large amounts of power into the main ac grid at points where the strength of the ac connection is low. The efficient and stable performance of such a power scheme is related to the capability of the control applied to retain the power extraction close to the maximum and simultaneously to regulate the dc-side voltage as well as the ac-side voltage magnitude at the weak ac connection point. This is implemented by designing the controllers of the voltage source inverters (VSIs) in a manner that reliably satisfies the above tasks. To this end, decentralized cascaded control schemes, driven by novel, locally implemented phase locked loops (PLLs), suitable to work in weak ac connections, are proposed for the VSI performance regulation by using new fast inner-loop proportional-integral (PI) current controllers. A decisive innovation is proposed by inserting an extra damping term in the inner-loop controllers to guarantee stability and convergence to the desired equilibrium. This is analytically proven by a rigorous analysis based on the entire nonlinear system model, where advanced Lyapunov-based methods are deployed in detail. As a good transient response of the VSI interface is indeed critical for the energy and grid system management, the conducted simulation and experimental results confirm that the proposed scheme efficiently supports the ac- and dc-side voltages of the VSI under different varying conditions in the power production or any voltage changes of the main grid.
Panos C. Papageorgiou; Konstantinos F. Krommydas; Antonio T. Alexandridis. Validation of Novel PLL-driven PI Control Schemes on Supporting VSIs in Weak AC-Connections. Energies 2020, 13, 1373 .
AMA StylePanos C. Papageorgiou, Konstantinos F. Krommydas, Antonio T. Alexandridis. Validation of Novel PLL-driven PI Control Schemes on Supporting VSIs in Weak AC-Connections. Energies. 2020; 13 (6):1373.
Chicago/Turabian StylePanos C. Papageorgiou; Konstantinos F. Krommydas; Antonio T. Alexandridis. 2020. "Validation of Novel PLL-driven PI Control Schemes on Supporting VSIs in Weak AC-Connections." Energies 13, no. 6: 1373.
A new approach and a novel solution to the voltage control problem of a dc/dc boost converter feeding an arbitrary constant power load (CPL) is developed. Particularly, as CPLs exhibit negative incremental resistance, a fact that in combination with the nonlinear nature of a converter/CPL system creates ad hoc stability problems, a nonlinear control design is proposed with main purposes: i) to be effective on regulating the output voltage regardless of the power absorbed, ii) to be easily implemented as a feedback loop from measurable states and outputs. In the feedback loop the measurable current at the power load side is fed back diminishing the need to apply any adaptation or other complicated mechanism for estimating the power absorbed by the CPL. Hence, the proposed controller analysis is based on the complete closed-loop nonlinear model instead of using standard linearized techniques and asymptotic stability is proven by applying suitable Lyapunov methods. This design approach extends the controller validity in a wide range while in practice it can be easily realized. The stable and good performance of the controller is finally evaluated by simulations taken with various CPL levels.
Panos C. Papageorgiou; Antonio T. Alexandridis. Voltage Stabilization of dc/dc Converter-driven Constant Power Loads via Feeding-back the Output Measured Current. IFAC-PapersOnLine 2020, 53, 13442 -13447.
AMA StylePanos C. Papageorgiou, Antonio T. Alexandridis. Voltage Stabilization of dc/dc Converter-driven Constant Power Loads via Feeding-back the Output Measured Current. IFAC-PapersOnLine. 2020; 53 (2):13442-13447.
Chicago/Turabian StylePanos C. Papageorgiou; Antonio T. Alexandridis. 2020. "Voltage Stabilization of dc/dc Converter-driven Constant Power Loads via Feeding-back the Output Measured Current." IFAC-PapersOnLine 53, no. 2: 13442-13447.
A novel, analytic design method for full state observers of nonlinear Lipschitz systems with their nonlinear term bounded, is considered. In standard procedures, the Lipschitz constant of the nonlinear term imposes strict restrictions on the observer gain matrix stable selection and introduces a further uncertainty in the design, caused by the heuristic manner of this selection. As shown in the paper, when the system nonlinear term is additionally bounded, which is a common situation for many real world systems such as manipulators in robotics and generators in power systems, the Lipschitz constant restriction is fully relaxed. Under these circumstances, a direct design approach is proposed that assigns the observer linear part eigenvalues at a common, specific, negative real position on the left of the system poles. The whole procedure is conducted by simply solving a Lyapunov-type equation that simultaneously constructs the suitable corresponding gain matrix of the observer. The validity of the method and the enhanced observer performance are verified by simulation results conducted on a fundamental power system example.
Panos C. Papageorgiou; Antonio T. Alexandridis. Simplifying the Design of Lipschitz Observers by Applying a Novel Batch Pole Assignment Approach. IFAC-PapersOnLine 2020, 53, 4163 -4168.
AMA StylePanos C. Papageorgiou, Antonio T. Alexandridis. Simplifying the Design of Lipschitz Observers by Applying a Novel Batch Pole Assignment Approach. IFAC-PapersOnLine. 2020; 53 (2):4163-4168.
Chicago/Turabian StylePanos C. Papageorgiou; Antonio T. Alexandridis. 2020. "Simplifying the Design of Lipschitz Observers by Applying a Novel Batch Pole Assignment Approach." IFAC-PapersOnLine 53, no. 2: 4163-4168.
In stability studies, the response of a system enforced by external, known or unknown, inputs is of great importance. Although such an analysis is quite easy for linear systems, it becomes a cumbersome task when nonlinearities exist in the system model. Nevertheless, most of the real-world systems are externally enforced nonlinear systems with nonzero equilibriums. Representative examples in this category include power systems, where studies on stability and convergence to equilibrium constitute crucial objectives. Driven by this need, the aim of the present work is twofold: First, to substantially complete the theoretical infrastructure by establishing globally valid sufficient conditions for externally enforced nonlinear systems that converge to nonzero equilibriums and, second, to deploy an efficient method easily applicable on practical problems as it is analyzed in detail on a typical power system example. To that end, in the theoretical first part of the paper, a rigorous nonlinear analysis is developed. Particularly, starting from the well-established nonlinear systems theory based on Lyapunov techniques and on the input-to-state stability (ISS) notion, it is proven after a systematic and lengthy analysis that ISS can also guarantee convergence to nonzero equilibrium. Two theorems and two corollaries are established to provide the sufficient conditions. As shown in the paper, the main stability and convergence objectives for externally enforced systems are fulfilled if simple exponential or asymptotic converging conditions can be proven for the unforced system. Then, global or local convergence is established, respectively, while for the latter case, a novel method based on a distance-like measure for determining the region of attraction (RoA) is proposed. The theoretical results are examined on classic power system generation nonlinear models. The power system examples are suitably selected in order to effectively demonstrate the proposed method as a stability analysis tool and to validate all the particular steps, especially that of evaluating the RoA. The examined system results clearly verify the theoretical part, indicating a rather wide range of applications in power systems.
Antonio T. Alexandridis. Studying State Convergence of Input-to-State Stable Systems with Applications to Power System Analysis. Energies 2019, 13, 92 .
AMA StyleAntonio T. Alexandridis. Studying State Convergence of Input-to-State Stable Systems with Applications to Power System Analysis. Energies. 2019; 13 (1):92.
Chicago/Turabian StyleAntonio T. Alexandridis. 2019. "Studying State Convergence of Input-to-State Stable Systems with Applications to Power System Analysis." Energies 13, no. 1: 92.
Electric vehicles (EVs), during a route, should normally operate at the desired speed by effectively controlling the power that flows between their batteries and the electric motor/generator. To implement this task, in this paper, the voltage source AC/DC converter is considered as a controlled power interface between the electric machine and the output of the DC storage device; the DC/DC converter is used to automatically regulate the battery operating condition in accordance to the profile of the acting on the vehicle wheels, unknown external torque. Particularly, the speed is continuously regulated by the vehicle driver via the pedal while all other regulations for absorbing or regenerating energy are internally controlled. The driver command is acting as speed reference input on a PI outer-loop motor speed controller which, in its turn, drives a fast P inner-loop current controller operating in cascaded mode. In a similar manner, the machine and the battery performance are self-regulated by a pure PI current controller that achieves maximum electric torque per ampere operation of the motor and by a PI/P cascaded scheme for the DC-voltage/battery–current regulation, respectively. In order to exclude any possibility of instabilities and adverse impacts between the different parts, a rigorous analysis is deployed on the complete electromechanical system that involves the motor, the batteries, the converter dynamic models and the proposed controllers. Modeling the system in Euler–Lagrange nonlinear form and applying sequentially suitable Lyapunov techniques and the time-scale separation principle, a systematic method for tuning the gains of the inner- and outer-loop controllers is derived. Therefore, the proposed controller design procedure guarantees asymptotic stability by considering the accurate system model as a whole. Finally, the proposed approach is validated by simulating realistic route conditions, performed under unknown external torque variations.
Jemma J. Makrygiorgou; Antonio T. Alexandridis. Power Electronic Control Design for Stable EV Motor and Battery Operation during a Route. Energies 2019, 12, 1990 .
AMA StyleJemma J. Makrygiorgou, Antonio T. Alexandridis. Power Electronic Control Design for Stable EV Motor and Battery Operation during a Route. Energies. 2019; 12 (10):1990.
Chicago/Turabian StyleJemma J. Makrygiorgou; Antonio T. Alexandridis. 2019. "Power Electronic Control Design for Stable EV Motor and Battery Operation during a Route." Energies 12, no. 10: 1990.
Direct current (DC) distribution systems and DC microgrids are becoming a reliable and efficient alternative energy system, compatible with the DC nature of most of the distributed energy resources (DERs), storage devices and loads. The challenging problem of redesigning an autonomous DC-grid system in view of using energy storage devices to balance the power produced and absorbed, by applying simple decentralized controllers on the electronic power interfaces, is investigated in this paper. To this end, a complete nonlinear DC-grid model has been deployed that includes different DC-DERs, two controlled parallel battery branches, and different varying DC loads. Since many loads in modern distribution systems are connected through power converters, both constant power loads and simple resistive loads are considered in parallel. Within this system, suitable cascaded controllers on the DC/DC power converter interfaces to the battery branches are proposed, in a manner that ensures stability and charge sharing between the two branches at the desired ratio. To achieve this task, inner-loop current controllers are combined with outer-loop voltage, droop-based controllers. The proportional-integral (PI) inner-loop current controllers include damping terms and are fully independent from the system parameters. The controller scheme is incorporated into the system model and a globally valid nonlinear stability analysis is conducted; this differs from small-signal linear methods that are valid only for specific systems, usually via eigenvalue investigations. In the present study, under the virtual cost of applying advanced Lyapunov techniques on the entire nonlinear system, a rigorous analysis is formulated to prove stability and convergence to the desired operation, regardless of the particular system characteristics. The theoretical results are evaluated by detailed simulations, with the system performance being very satisfactory.
Despoina I. Makrygiorgou; Antonio T. Alexandridis. Stability Analysis of DC Distribution Systems with Droop-Based Charge Sharing on Energy Storage Devices. Energies 2017, 10, 433 .
AMA StyleDespoina I. Makrygiorgou, Antonio T. Alexandridis. Stability Analysis of DC Distribution Systems with Droop-Based Charge Sharing on Energy Storage Devices. Energies. 2017; 10 (4):433.
Chicago/Turabian StyleDespoina I. Makrygiorgou; Antonio T. Alexandridis. 2017. "Stability Analysis of DC Distribution Systems with Droop-Based Charge Sharing on Energy Storage Devices." Energies 10, no. 4: 433.
The DC-DC boost converter is one of the simplest power electronic devices that has not been yet exploited in a wide range of industrial applications due to control design difficulties caused by its model inherent special structure. Such an industrial application is the DC motor speed regulation that is studied in the present work. Particularly, in this article, a novel, non-linear control scheme for the duty ratio input of the converter is proposed, which is extensively analyzed and experimentally tested. The proposed design, though non-linear, results in a very simple scheme, ensures that the duty ratio takes values exclusively in the permitted range [0,1), achieves precise speed regulation even in cases of high unknown load disturbances, and does not depend on system parameters and states. Simultaneously, the design is formulated in a manner that provides a closed-loop passive system, which, as proven in the article, satisfies all these assumptions and properties that make possible the application of a new advanced non-linear method that strongly connects passivity with stability. Thus, the boundedness of all the closed-loop states and the stability and convergence to the desired steady-state equilibrium are directly concluded. The theoretical analysis is verified through extended simulation and experimental results.
George C. Konstantopoulos; Antonio T. Alexandridis. Enhanced Control Design of Simple DC-DC Boost Converter-driven DC Motors: Analysis and Implementation. Electric Power Components and Systems 2015, 43, 1946 -1957.
AMA StyleGeorge C. Konstantopoulos, Antonio T. Alexandridis. Enhanced Control Design of Simple DC-DC Boost Converter-driven DC Motors: Analysis and Implementation. Electric Power Components and Systems. 2015; 43 (17):1946-1957.
Chicago/Turabian StyleGeorge C. Konstantopoulos; Antonio T. Alexandridis. 2015. "Enhanced Control Design of Simple DC-DC Boost Converter-driven DC Motors: Analysis and Implementation." Electric Power Components and Systems 43, no. 17: 1946-1957.
In this study, a new non-linear dynamic controller is proposed for regulating the output voltage of a DC/DC boost power converter in a stand-alone photovoltaic (PV) system. The controller provides directly the duty-ratio input of the converter, bounded in the permitted range, and as it is proven it achieves the desired voltage regulation independently from the PV source voltage, the converter parameters and the kind of the load. An appropriate mathematical analysis is used to indicate that the proposed control scheme guarantees closed-loop system stability with the state trajectories converging to the desired equilibrium. Particularly, using as generic concept the fundamental property of passivity of the original system, the proposed controller scheme results in a closed-loop system wherein (i) the passivity and damping properties are maintained and (ii) the conditions which exploit these properties in a manner that guarantees stability are met. Extended simulation and experimental results verify effectiveness of the controller for the case of a DC/DC boost converter with resistance-inductance load. The system performance, operating with the proposed non-linear (voltage) controller is compared with that obtained by implementing conventional cascaded (voltage–current) controllers under input voltage step disturbances or load variations. Finally, some experimental resuts for the case of a non-linear load consisted of a three-phase voltage source inverter and a three-phase resistance–inductance load are illustrated.
George C. Konstantopoulos; Antonio T. Alexandridis. Non‐linear voltage regulator design for DC/DC boost converters used in photovoltaic applications: analysis and experimental results. IET Renewable Power Generation 2013, 7, 296 -308.
AMA StyleGeorge C. Konstantopoulos, Antonio T. Alexandridis. Non‐linear voltage regulator design for DC/DC boost converters used in photovoltaic applications: analysis and experimental results. IET Renewable Power Generation. 2013; 7 (3):296-308.
Chicago/Turabian StyleGeorge C. Konstantopoulos; Antonio T. Alexandridis. 2013. "Non‐linear voltage regulator design for DC/DC boost converters used in photovoltaic applications: analysis and experimental results." IET Renewable Power Generation 7, no. 3: 296-308.
Evangelos A. Androulidakis; Antonio T. Alexandridis; George C. Konstantopoulos; Antonis Alexandridis. Studying Complexity for a Modified Dissipative Hamiltonian System: From Lyapunov Stability at the Origin to a Limit Cycle and Chaos. IFAC Proceedings Volumes 2013, 46, 617 -622.
AMA StyleEvangelos A. Androulidakis, Antonio T. Alexandridis, George C. Konstantopoulos, Antonis Alexandridis. Studying Complexity for a Modified Dissipative Hamiltonian System: From Lyapunov Stability at the Origin to a Limit Cycle and Chaos. IFAC Proceedings Volumes. 2013; 46 (2):617-622.
Chicago/Turabian StyleEvangelos A. Androulidakis; Antonio T. Alexandridis; George C. Konstantopoulos; Antonis Alexandridis. 2013. "Studying Complexity for a Modified Dissipative Hamiltonian System: From Lyapunov Stability at the Origin to a Limit Cycle and Chaos." IFAC Proceedings Volumes 46, no. 2: 617-622.
A generalized nonlinear control scheme suitable to regulate any state variable at any desired reference value, for a class of nonlinear Hamiltonian-passive systems that includes switching power devices, is presented. The proposed controller acts as a special nonlinear oscillator, uses as feedback only the state variable that has to be regulated, renders the Hamiltonian-passive structure of the entire system, and regulates the nonlinear system to any nonzero desired equilibrium independently from its parameters and characteristics. Particularly, it is proven that under some common assumptions, the system states consisting of the controller states plus the original system states, are bounded for constant or piecewise constant external inputs. Under the same assumptions, it is established and proven that for these systems there exists a general, bounded, differentiable, nonincreasing storage function. Thus, LaSalle's invariance principle can be directly applied to prove convergence to the desired equilibrium. Although this storage function can be really constructed as a suitably switching function, its explicit derivation is not necessary for the controller design; it is only needed to guess that such a storage function exists. This constitutes the main contribution of this brief since, in order to implement the proposed controller, one has simply to check whether some initial assumptions are satisfied. The simulation and experimental results conducted for the case of a dc-dc boost converter system with resistance-inductance load verify the proposed design approach.
George C. Konstantopoulos; Antonio T. Alexandridis. Generalized Nonlinear Stabilizing Controllers for Hamiltonian-Passive Systems With Switching Devices. IEEE Transactions on Control Systems Technology 2012, 21, 1479 -1488.
AMA StyleGeorge C. Konstantopoulos, Antonio T. Alexandridis. Generalized Nonlinear Stabilizing Controllers for Hamiltonian-Passive Systems With Switching Devices. IEEE Transactions on Control Systems Technology. 2012; 21 (4):1479-1488.
Chicago/Turabian StyleGeorge C. Konstantopoulos; Antonio T. Alexandridis. 2012. "Generalized Nonlinear Stabilizing Controllers for Hamiltonian-Passive Systems With Switching Devices." IEEE Transactions on Control Systems Technology 21, no. 4: 1479-1488.
George C. Konstantopoulos; Antonio T. Alexandridis. Simplified Nonlinear Control Design and Stability Analysis for Controlled Voltage Fed Induction Motors. Software Engineering 2012, 1 .
AMA StyleGeorge C. Konstantopoulos, Antonio T. Alexandridis. Simplified Nonlinear Control Design and Stability Analysis for Controlled Voltage Fed Induction Motors. Software Engineering. 2012; ():1.
Chicago/Turabian StyleGeorge C. Konstantopoulos; Antonio T. Alexandridis. 2012. "Simplified Nonlinear Control Design and Stability Analysis for Controlled Voltage Fed Induction Motors." Software Engineering , no. : 1.
A simple and novel dynamic circuit model for a proton exchange membrane (PEM) fuel cell suitable for the analysis and design of power systems is presented. The model takes into account phenomena like activation polarization, ohmic polarization, and mass transport effect present in a PEM fuel cell. The proposed circuit model includes three resistors to approach adequately these phenomena; however, since for the PEM dynamic performance connection or disconnection of an additional load is of crucial importance, the proposed model uses two saturable inductors accompanied by an ideal transformer to simulate the double layer charging effect during load step changes. To evaluate the effectiveness of the proposed model its dynamic performance under load step changes is simulated. Experimental results coming from a commercial PEM fuel cell module that uses hydrogen from a pressurized cylinder at the anode and atmospheric oxygen at the cathode, clearly verify the simulation results.
Stavros Lazarou; Eleftheria Pyrgioti; Antonio T. Alexandridis. A simple electric circuit model for proton exchange membrane fuel cells. Journal of Power Sources 2009, 190, 380 -386.
AMA StyleStavros Lazarou, Eleftheria Pyrgioti, Antonio T. Alexandridis. A simple electric circuit model for proton exchange membrane fuel cells. Journal of Power Sources. 2009; 190 (2):380-386.
Chicago/Turabian StyleStavros Lazarou; Eleftheria Pyrgioti; Antonio T. Alexandridis. 2009. "A simple electric circuit model for proton exchange membrane fuel cells." Journal of Power Sources 190, no. 2: 380-386.