List of Articles perturbation

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  1 - A New Calibration Method for SAR Analog-to-Digital Converters Based on All Digital Dithering
  Ebrahim Farshidi Shabnam Rahbar
  10.7508/jist.2017.17.001
  In this paper a new digital background calibration method for successive approximation register analog to digital converters is presented. For developing, a perturbation signal is added and also digital offset is injected. One of the main advantages of this work is that More

  In this paper a new digital background calibration method for successive approximation register analog to digital converters is presented. For developing, a perturbation signal is added and also digital offset is injected. One of the main advantages of this work is that it is completely digitally and eliminates the nonlinear errors between analog capacitor and array capacitors due to converter’s capacitors mismatch error by correcting the relative weights. Performing of this digital dithering method does not require extra capacitors or double independent converters and it will eliminate mismatches caused by these added elements. Also, No extra calibration overhead for complicated mathematical calculation is needed. It unlike split calibration, does not need two independent converters for production of two specified paths and it just have one capacitor array which makes it possible with simple architecture. Furthermore, to improve DNL and INL and correct the missing code error, sub radix-2 is used in the converter structure. Proposed calibration method is implemented by a 10 bit, 1.87-radix SAR converter. Simulation results with MATLAB software show great improvement in static and dynamic characteristics in applied analog to digital converter after calibration. So, it can be used in calibration of successive approximation register analog to digital converters. Manuscript profile
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  2 - Improved Maximum Power Point Tracking Off-Grid Solar Panels
    A. R. Reisi
  Solar panels exhibit non-linear current–voltage characteristics producing maximum power at only one particular operating point. The maximum power point changes with temperature and light intensity variations. Different methods have been introduced for tracking the maxim More

  Solar panels exhibit non-linear current–voltage characteristics producing maximum power at only one particular operating point. The maximum power point changes with temperature and light intensity variations. Different methods have been introduced for tracking the maximum power point based on offline and online methods. In this paper a new method is presented to improve the performance of maximum power point tracking in off-grid solar panels. The proposed algorithm is a combination of two loops, set point calculation and fine tuning loops. First the set point loop approximates the maximum power using offline calculation of the open circuit voltage. The exact amount of the maximum power will, then, be tracked by the fine tuning loop which is based on perturbation and observation (P&O) method. The proposed method is simulated in Matlab/Simulink environment and experimentally verified using a laboratory prototype. In maximum power point tracking, the effects of frequency variation and disturbance amplitude on dynamic response and steady state performance are examined. Simulation and experimental results are compared with other methods and the effectiveness of the proposed method is evaluated. Manuscript profile
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  3 - Controller Design and Asymptotic Stability Analysis of a Buck Converter with a Cascade Control Structure Using Singular Perturbation Theory
  Sajad Azarastemal Mohammad Hejri
  This paper presents the theoretical proof for the closed-loop asymptotic stability of a DC-DC buck converter based on singular perturbation theory. Due to the two-time scales structure of this converter with fast and slow dynamics, a cascade control structure is used to More

  This paper presents the theoretical proof for the closed-loop asymptotic stability of a DC-DC buck converter based on singular perturbation theory. Due to the two-time scales structure of this converter with fast and slow dynamics, a cascade control structure is used to control it. This controller has two control loops: an outer loop to control the output voltage based on the proportional-integral control and an inner loop to control the inductor current based on the sliding mode control. The controllers in the loops are designed based on perturbation theory to meet the constraints of the converter and ensure the asymptotic stability of the closed-loop system over a wide range of initial conditions. For validation, the proposed control design method is simulated for a typical buck converter in the MATLAB-SIMULINK environment. The simulation results show that by properly selecting the PI controller coefficients in the outer loop, the problem requirements are met, and the asymptotic stability of the closed-loop system is guaranteed in a wide range of the converter initial conditions. Furthermore, the system robustness against load uncertainty and input disturbances as well as the voltage reference tracking are evaluated, and the proposed structure is compared with a PI-PI structure. Manuscript profile