Industrial Electronics
Saleh Mohammadi; Hamid Reza Izadfar; Naser Eskandarian
Abstract
This research aims to provide a comprehensive review of various CCM control strategies for flyback inverters. The study is carried out based on published data in reports, papers and other available online documents. The introduced control strategies make use of different approaches to dominate the constraints ...
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This research aims to provide a comprehensive review of various CCM control strategies for flyback inverters. The study is carried out based on published data in reports, papers and other available online documents. The introduced control strategies make use of different approaches to dominate the constraints on determining the feedback control system gains caused by the zero put on right-half-plane (RHP) and dynamics of LC filter. Thus, the tracking of the considered output current is accurately implemented and the introduced control systems carry out the attenuation of disturbances. Moreover, zero steady-state error and the stability requirements are fulfilled by properly regulating the control signal. The best control structure should be enough fast employing the fewest number of delays in its structure resulting the burden in computational system to be considerably decreased.
Power systems
Saeed Abazari
Abstract
This study examines stability improvement of the power system which includes Double Feed Induction Generators (DFIGs) and Static Series Synchronous Compensator (SSSC). The proposed nonlinear controller is designed based on the terminal sliding mode control theory. A sliding mode observer is also developed ...
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This study examines stability improvement of the power system which includes Double Feed Induction Generators (DFIGs) and Static Series Synchronous Compensator (SSSC). The proposed nonlinear controller is designed based on the terminal sliding mode control theory. A sliding mode observer is also developed to remove the need to access the information of all the state variables. The final closed-loop of the power system modeling is robust against parameter variations and uncertainties. The limitations of the control signals in the process of controller design are also considered. The application of such a method increases the stability margins and results in higher robustness degrees. A comparison with other nonlinear approaches such as back-stepping and feedback linearization approaches is carried out. The results show the faster and more reliable convergence rate of the power system-controlled trajectories to reach back to the equilibrium point after occurring a sudden fault. The results are obtained by performing a simulation on the standard 39-Bus, 10 machines NEW ENGLAND power system.
Industrial Electronics
Mehran Jami
Abstract
In electric vehicles (EVs), the small size of the dc link capacitor results in significant voltage deviations when there are changes in load or uncertain fluctuations from the power resources. This causes a decline in voltage quality. To address the issue of low inertia, this study suggests the use of ...
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In electric vehicles (EVs), the small size of the dc link capacitor results in significant voltage deviations when there are changes in load or uncertain fluctuations from the power resources. This causes a decline in voltage quality. To address the issue of low inertia, this study suggests the use of a fast-responding energy storage system, such as a supercapacitor (SC), which can replicate inertial responses through a specified control algorithm. A virtual capacitor and a virtual conductance are presented in this paper, which are implemented in the inner loop control, specifically the current loop control of SC, to effectively emulate inertia and damping and improves the battery lifetime by reducing the rate of charge and discharge. To assess the stability of the EV, a comprehensive small-signal model is developed, and the acceptable range of inertia response parameters is determined through eigenvalues analysis of the system. Numerical simulations are conducted to demonstrate the performance of the proposed control structure.
Control
Majid Akbarian; Naser Pariz
Abstract
Lyapunov's theorem is the basic criteria to establish the stability properties of the nonlinear dynamical systems. In this method, it is a necessity to find the positive definite functions with negative definite or negative semi-definite derivative. These functions that named Lyapunov functions, form ...
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Lyapunov's theorem is the basic criteria to establish the stability properties of the nonlinear dynamical systems. In this method, it is a necessity to find the positive definite functions with negative definite or negative semi-definite derivative. These functions that named Lyapunov functions, form the core of this criterion. The existence of the Lyapunov functions for asymptotically stable equilibrium points is guaranteed by converse Lyapunov theorems. On the other hand, for the cases where the equilibrium point is stable in the sense of Lyapunov, converse Lyapunov theorems only ensure non-smooth Lyapunov functions. In this paper, it is proved that there exist some autonomous nonlinear systems with stable equilibrium points that despite stability don’t admit convex Lyapunov functions. In addition, it is also shown that there exist some nonlinear systems that despite the fact that they are stable at the origin, but do not admit smooth Lyapunov functions in the form of V(x) or V(t,x) even locally. Finally, a class of non-autonomous dynamical systems with uniform stable equilibrium points, is introduced. It is also proven that this class do not admit any continuous Lyapunov functions in the form of V(x) to establish stability.
Control
Gholamreza Bidari; Naser Pariz; Ali Karimpour
Abstract
This paper investigates the stabilization problem of an autonomous Linear Time Invariant (LTI) switched system with interval uncertainty and unstable subsystems. It is proved that the system would be stable by using a common Lyapanov function whose derivative is negative and bounded by a quadratic function ...
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This paper investigates the stabilization problem of an autonomous Linear Time Invariant (LTI) switched system with interval uncertainty and unstable subsystems. It is proved that the system would be stable by using a common Lyapanov function whose derivative is negative and bounded by a quadratic function within activation regions of each subsystem. First, a sufficient condition for the stability of an Linear Time Invariant switched system with interval uncertainty, based on the convex analysis and interval set theoretical approach, is presented and proved. Moreover, conservatism in the stability robustness bound is obtained. Then, a switching control law is designed to shift the Linear Time Invariant switched system among subsystems to ensure the decrease of the Lyapanov function within the state space. Finally, in order to decrease the switching frequency and to avoid chattering, the switching law is modified. Two examples are included to demonstrate the effectiveness of the theoretical findings.
