Modelling and Passivity-based Control of a Non-isolated DC-DC Converter in a Fuel Cell System

This paper presents the model of a fuel cell and the design and simulation of a cascade of two DC-DC converters. First, a detailed mathematical model of fuel cell is presented and simulated. Then, a nonlinear model of the whole controlled system is developed and a robust nonlinear controller of currents is synthesized using a passivity-based control. A formal analysis based on Lyapunov stability and average theory is developed to describe the control currents loops performances. A classical PI controller is used for the voltages loops. The simulation models have been developed and tested in the MATLAB/SIMULINK. Simulated results are displayed to validate the feasibility and the effectiveness of the proposed strategy

Design and investigations of MPPT strategies for a wind energy conversion system based on doubly fed induction generator

The purpose of this work is to design and to discuss various strategies to optimize the production of a wind energy conversion chain based on the doubly fed induction generator (DFIG), by capturing the maximum power at the wind turbine, using maximum power point tracking (MPPT) and pitch control. The proposed controls allow the generator to monitor the optimal operating points of the turbines regardless of wind speed variations, system parameters disturbance, and parameters variation. Simulation of WECS based on a 1.5 MW wound rotor induction generator under MATLAB/SIMULINK is carried out using the PI controller (PIC), RST controller and fuzzy logic controller (FLC). Analysis and comparisons are made for different operating scenarios: Reference tracking, robustness under variable wind speed conditions and parameters variation. The application of FLC provides a very interesting outcome for the robustness and the dynamic challenges

A new structure of a wide band bridge power limiter

In this work, new design and simulation of a microstrip power limiter based on Schottky diode is presented. The proposed circuit is a zero bias power limiter built by associating a transmission line in parallel to a four Schottky rectifier bridge circuit. The first circuit using a single stage rectifier is analyzed and simulated. To improve this single stage, a second and final limiter is designed with two stages rectifier. Simulation results for the final circuit show an ideal limiter behavior and good performance of limiting rate up to 20dB for a threshold input power varying from 5 dBm to 30 dBm. While insertion loss remains low at small signal

Integral Backstepping Based Nonlinear Control for Maximum Power Point Tracking and Unity Power Factor of a Grid Connected Hybrid Wind-Photovoltaic System

This paper proposes a novel integral backstepping-based nonlinear control strategy for a grid-connected wind-photovoltaic hybrid system. Firstly, detailed three-phase models of the hybrid system elements are presented, and then an overall state-space model is derived. Secondly, nonlinear control laws for the hybrid system’s converters are developed with the aim of ensuring maximum extraction of the available renewable energy, stabilizing the DC bus voltage and guaranteeing the operation of the hybrid system at unity power factor. The overall stability of the closed-loop system is demonstrated on the basis of Lyapunov’s stability theory. Comprehensive simulations, using the MATLAB/Simulink software environment, are carried out to assess the effectiveness of the proposed control methodology. The simulation results obtained confirm that the proposed control strategy offers high efficiency in various operating modes of the hybrid generation system

Comparison of backstepping, sliding mode and PID regulators for a voltage inverter

In the present paper, an efficient and performant nonlinear regulator is designed for the control of the pulse width modulation (PWM) voltage inverter that can be used in a standalone photovoltaic microgrid. The main objective of our control is to produce a sinusoidal voltage output signal with amplitude and frequency that are fixed by the reference signal for different loads including linear or nonlinear types. A comparative performance study of controllers based on linear and non-linear techniques such as backstepping, sliding mode, and proportional integral derivative (PID) is developed to ensure the best choice among these three types of controllers. The performance of the system is investigated and compared under various operating conditions by simulations in the MATLAB/Simulink environment to demonstrate the effectiveness of the control methods. Our investigation shows that the backstepping controller can give better performance than the sliding mode and PID controllers. The accuracy and efficiency of the proposed backstepping controller are verified experimentally in terms of tracking objectives

Integral Backstepping Control for Maximum Power Point Tracking and Unity Power Factor of a Three Phase Grid Connected Photovoltaic System

This paper presents a robust control strategy for a grid connected photovoltaic system with a boost converter by using an integral Backstepping method based on a nonlinear state model, which guarantees the Lyapunov stability of the global system. The system has tracked precisely the maximum power point, with a very fast response and the unit power factor has been observed under different atmospheric conditions. Moreover, the best advantage of the controller is that it’s a good corrector of the grid perturbation and system parameter disturbance. The simulation result has demonstrated the performance of this strategy

A novel printed multiband low cost antenna for WLAN and WiMAX applications

In this paper, a star-shaped microstrip patch antenna with modified ground structure consisting of an F-shaped slot printed in the ground is presented. The purpose of this design is to achieve and validate this microstrip multiband antenna. The entire area of the proposed antenna is 50x50mm2 and is printed on an FR-4 substrate and fed by a 50 Ohm microstrip line. This antenna has been analyzed and simulated for the WLAN and WiMAX applications. Simulation results show that the antenna has a good matching input impedance bandwidths for, S11<=-10 dB, covering the WLAN at 2.4/5.2 GHz and WiMAX at 3.5 GHz. Simulation has been done by using three different electromagnetic solvers for comparison CST-MW, Ansoft’s HFSS and ADS. After the realization, we have tested and validated this antenna. The measurement results of the antenna present a good agreement with the numerical results

A New design of a microstrip antenna with modified ground for DCS and WiMAX applications

This paper presents a novel design of a pentagonal-shaped planar dual-band monopole antenna with a modified ground structure. The validated antenna is compact with a size of 57x50x1,6 mm cube. It is printed on an FR-4 substrate and fed by a 50 Ohm microstrip line. The final circuit operates in the DCS frequency band at 1.8 GHz and the WiMAX at 3.5 GHz. To achieve such antenna, we have used different optimization methods integrated in CST Microwave Studio. The obtained results are compared with another electromagnetic solver Ansoft’s HFSS. After the realization, we have tested and validated this antenna. The measurement results present an agreement with the numerical results

Backstepping based power control of a three-phase Single-stage Grid-connected PV system

In order to reduce costs while maintaining superior performance, this paper presents a new control methodology of a three-phase grid connected photovoltaic system without using the intermediary DC/DC converter. Based on the synchronized nonlinear model of the whole photovoltaic system, two controllers have been proposed for the three-phase inverter in order to ensure the operation of the PV system at the maximum power point with unity power factor and minimum grid disturbance. Grid synchronization has been ensured by a three-phase 2nd order PLL (Phase-Locked Loop). The stability of each controller is demonstrated by means of Lyapunov analysis and evaluated under changing atmospheric conditions using the Matlab/Simulink environment, the simulation results clearly demonstrate the performance provided by each controller