Abdelkader Mami

Sliding mode controller for buck-boost dc-dc converter in PV grid-connected system

This paper presents new alternatives of design and control for three-phase grid connected photovoltaic systems GCPS. In this work, the photovoltaic generation source PVG is connected to the main electric grid via two power electronics stages. The first stage consists on a buck-boost dc-dc converter that insures impedance adaptation between the PVG and the grid. This converter is controlled by the sliding mode control SMC to track the dc reference voltage required by the main grid. The second stage is composed by a dc-bus and a three-phase voltage inverter used to interface the PVG with the grid utility. The inverter is controlled by the Direct Power Control DPC in order to inject the PV power into the main grid with a high quality power factor. The model of the GCPS has been implemented in the Matlab/Simulink software and simulation studies have been presented to demonstrate the effectiveness of the proposed study.

Design, Modeling and Energy Management of a PEM Fuel Cell / Supercapacitor Hybrid Vehicle

This work concerns the study and the modeling of hybrid Proton Exchange Membrane (PEM) Fuel Cell electric vehicle. In fact, the paper deals with the model description of the powertrain which includes two energy sources: a PEM Fuel Cell as a primary source and a supercapacitor as a secondary source. The architecture is two degrees of freedom permitting a stability of the DC bus voltage. The hybridation of primary source with an energy storage system can improve vehicle dynamic response during transients and hydrogen consumption. The proposed energy management algorithm allows us to have a minimum hydrogen consumption. This algorithm is based on supercapacitor state of charge (SOC) control and acceleration/deceleration phases making possible braking energy recovery. The proposed model is simulated and tested using Matlab/Simulink software allowing rapid transitions between sources. The obtained results with the New European Driving Cycle (NEDC) cycle demonstrate a 22% gain in hydrogen consumption.

Pseudo Bond Graph Modeling and Experimental Investigation of Thermal Transfers Inside a Household Refrigerator

This paper proposes a pseudo bond graph model of thermal transfers by natural convection inside a household refrigerator. It has two inputs: the ambient temperature and the temperature at the level of the evaporator wall. The latter assesses the functioning of the compressor cycles. A performance comparison, with the experimental data, was carried out in order to verify the model, in which, real measurements are used to modulate the evaporator temperature source. The simulation results show the effectiveness of the proposed approach.

FPGA implementation of predictive control

In this paper, we propose an implementation of a synthesizable VHDL program of generalized predictive control (GPC) without constraints on a map XC3S700A Xilinx Starter Kit using the Xilinx ISE 10.1 software. The control strategy was applied to a second order state system. The VHDL language was used as a programming tool. Real variables were described with the fixed-point representation to overcome the overflow problems during the computations in the VHDL program. The use of FPGA circuits presents a good choice regarding to the problem of computation time encountered in predictive algorithms. A GPC Matlab program was also implemented in order to make a performance comparison. The simulation results show a good set-point tracking.

Solutions based on renewable energy and technology to improve the performance of refrigeration systems

This paper presents a review of recent studies interesting in improving the energy efficiency and cooling quality of refrigeration systems, especially, household refrigerators, air conditioners, and cold storages. They proposed solutions based on renewables such as solar, geothermal, and natural cold through designing advanced plants. Their overall improvement in energy management could bring savings of up to 95% in appropriate conditions and according to the structure of the refrigeration installation. The paper also gives statistics about the energy consumption of refrigeration systems and the interest of using renewables in this field.

Temperature control in a cavity of refrigeration using PI controller and predictive control

A PI controller and a generalized predictive control strategy of the temperature inside a cavity of refrigeration are proposed, using Matlab/Simulink environment. The control strategies were applied to a third-order discrete state space system, which computes the internal air temperature according to the temperature at the level of the evaporator exchanger, under the influence of the ambient temperature. The system was obtained by linearization of a pseudo bond graph model of thermal transfers inside the refrigeration cavity. The simulation results were compared to those of the pseudo bond graph model for a classical thermostatic control. The used control strategies allowed an average energy saving of about 70% compared with the conventional on/off controller.The predictive control was more efficient than the PI controller of 23.33 %.

Study of an electronic load for measuring the internal impedance of a PEM fuel cell

In order to further understanding the behavior of PEM fuel cell and optimize their performance, it is necessary to perform measurements in real time. The measure of internal impedance of a fuel cell in load is of great importance. In this work, we present the impedance measurement method of a PEM fuel cell by electrochemical impedance spectroscopy method (EIS), as well the study of an electronic load for the implementation of the measurement technique. The theoretical results are obtained by a simulation with PSPICE software.

Pseudo bond graph model of a thermo-hydraulic system

The paper presents a pseudo bond graph model of a thermo-hydraulic system which is composed by two warm and cold water pipes, a plastic tank and an evacuation pipe. This model is designed on 20sim software and it allows varying the temperature, inside the tank, by acting on the mass flows of the warm and cold water, as well as on the evacuation pipe. A simulation is done for constant and variable water mass flows to show the efficiency of this bond graph model.

Arnoldi model reduction for switched linear systems

In this paper we present a new method of reduction for large-scale switched system, which is an important class of hybrid and non linear systems. In this work, we focus on linear switched systems. This new method is based on the generation of Krylov subspace by the use of the Arnoldi algorithm, which is numerically efficient and applicable for any order, from which we solve the problem of H∞ model reduction. We take one example to evaluate this method.

Observability and Controllability Study of a Household Refrigerator Exposed to an Outdoor Cold Airflow Using Bond Graph Approach

The present paper studies the properties of observability and controllability using Bond Graph (BG) approach. It is especially applied to a pseudo BG model that describes the thermal transfers in a household refrigerator compartment exposed to an outdoor natural cold airflow. This latter is spread out in an installation, which consists of a cavity covering the side wall of the appliance and connected to inlet and outlet ducts through two openings. The study results show that the pseudo BG model is observable and controllable in time-varying (TV) systems using the concept of duality.