Lotfi Krichen

Design and energy control of stand-alone hybrid wind/photovoltaic/fuel cell power system supplying a desalination unit

Faced with increasing trend of water demand and decreasing resources of fossil fuels and their high costs, desalination units based on renewable energies have become the best solution to face this challenge. This paper aims to investigate the design and the operation strategy of stand-alone hybrid renewable power generation system supplying a desalination unit which feeds the Kerkennah islands (Tunisia) with fresh water. The sizing of all the main hybrid system components such as photovoltaic generator, wind turbine, a fuel cell, and an electrolyzer is investigated in order to obtain some technical and economic profitability. In order to ensure the optimal use of the produced energy and satisfy the fresh water needs, a novel power management algorithm that allows controlling the energy flows within the system components is developed. Simulation results were carried out over the two months of January and July, and its results are shown in our paper. These results demonstrate the feasibility and the efficie...

Reduced order observer for permanent magnet synchronous generator in wind energy conversion system

This paper presents an approach to develop a simple reduced speed observer for permanent magnet synchronous generator (PMSG) in wind energy conversion system (WECS). The speed and rotor position estimation of the PMSG are obtained by only measuring phase voltage and current. Maximum wind energy extraction is achieved by running the wind turbine generator in variable-speed mode. The rotor speed is allowed to vary in sympathy with the wind speed by maintaining the tip speed ratio to the value that maximizes aerodynamic efficiency. Advantages of this mechanical sensorless control strategy for maximum power estimation are demonstrated by digital simulation of the WECS.

Demand side management of an isolated hybrid energy production unit supplying domestic loads

The purpose of this article is to develop a demand side management (DSM) of an isolated hybrid unit (IHU) supplying domestic loads. The action on load profile provides an efficient way to improve the energy management system associated to an autonomous smart home. This domestic IHU comprises a photovoltaic (PV) panel as principal source, a diesel engine as a buckup source and a storage system. Indeed, the action on some controllable loads can fully benefit from the renewable power and achieve savings and higher efficiency in energy consumer. In fact, the DSM algorithm uses the customer energy history, the available instantaneous PV energy and the state of charge of the storage system to switch between two appropriate modes: time shifting load mode and amplitude modulation load one. This management technique allows the consumer to minimize the installation initial cost and to extend the lifetime of system components. Simulation results show the effectiveness of the proposed DSM strategy.

Sizing of a stand-alone hybrid system supplying a desalination unit

Economic and environmental concerns over fossil fuels encourage the development of renewable energy. But to allow the penetration of intermittent energy sources, optimal sizing of hybrid renewable energy systems is quite necessary. This paper presents an optimal sizing algorithm which estimates the sizes of different components of hybrid photovoltaic/wind power generation system supplying a desalination unit. The optimal combination of the hybrid system is selected according to its technical and economic profitability. A case study is conducted to analyze a hybrid project, which is designed to supply a desalination unit feeding the Kerkennah islands (Tunisia) with fresh water.

Power management of an isolated hybrid energy production unit with super-capacitor

The aim of this paper is to propose a power control strategy of an isolated hybrid energy production unit. The proposed (wind / photovoltaic / diesel / super-capacitor) hybrid system is found to be the configuration to ensure a continuous feed of a three-phase load and to secure the storage system. An overall power management strategy is designed to manage power flows between the different energy sources and the storage unit. In this context, we used a control algorithm which describes four operating modes. The obtained simulation results are presented and discussed and the control strategy is validated for different scenarios.

Adaptive observer-based fault estimation for a DFIG based wind turbine system

This paper studies the problem of fault estimation using adaptive fault diagnosis observer method for a DFIG based wind turbine system. This adaptive fault estimation algorithm is proposed to enhance the rapidity and accuracy performance of fault estimation. In particular, an electrical fault scenario, the DFIG winding short circuit fault, is considered due to its high occurrence rates. Based on the fault estimation information, a fault compensator is designed based on fault information provided by the fault diagnosis scheme to guarantee the stability of the system, and it incorporates with a traditional controller to provide an online fault compensation of winding short circuit faults. Finally, the implementation of the proposed approach and the results obtained from its application to the DFIG based wind turbine system are presented to illustrate the efficiency of the proposed methodology.

Graphical interface development of a sizing algorithm of a photovoltaic/wind/hydrogen system

This paper presents a simulation graphical interface of a sizing algorithm of a hybrid renewable energy system. This algorithm has been developed for sizing the components of a stand-alone PV/wind/hydrogen system supplying a desalination unit which feeds the Kerkennah islands (Tunisia) with fresh water. The aim of this approach is to determine, among a list of commercially available system devices, all possible configurations of the hybrid system that would guarantee a reliable energy supply. The simulation and the display of all configurations obtained by this algorithm are performed by the graphical interface. This interface sorts the obtained combinations according to their investment cost in ascending order, selects the optimal solution and presents the various curves describing the behavior of the optimal hybrid system.

Action on the dynamic behavior of a washing machine in a renewable multi-agent system

This paper investigates the action on the dynamic behavior of a domestic washing machine in a multi-agent system. The purpose of this work is to develop a demand side management control strategy by modifying the washer power profile. This strategy leads to increase the renewable energy usage and to reduce peak demands by modifying the electrical profile of the consumer.

A new power ma nagement algorithm for a stand-alone hybrid system supplying a desalination unit

A renewable hybrid system coupled to a reverse osmosis desalination unit in southern Tunisia is studied. The hybrid system includes a photovoltaic generator, a wind turbine, a fuel cell and an electrolyzer. To allow a real penetration of intermittent energy sources and to satisfy the fresh water needs, a new power management algorithm allowing the control of the energy flow between the system components is developed. Two sub-algorithms are incorporated in this algorithm. These two sub-algorithms identify the production lines number operating at a pre-defined time interval and adjust the consumed power by the desalination unit. Simulation results are carried out over one year and present the different parameters describing the behavior of the system. These results demonstrate the feasibility and the efficiency of the used control strategy and the performance of the hybrid system.

Active power filter based on wind turbine for electric power system quality improvement

The increasing number of grid-connected non-linear loads causes more disruption problems to power grids. Indeed, these loads absorb periodic currents with different waveforms and consume reactive power which causes the emergence of harmonic distortion in the mains current and voltage levels that should be avoided. In order to solve this drawback, this paper presents a control scheme based on shunt active filter supplied by a wind turbine generator to compensate at the same time the harmonics currents and the reactive power caused by nonlinear loads. The aim of this compensation is to provide a high voltage quality at the point of common coupling (PCC) through a proper control of wind turbine distributed generators interface converters. The system is simulated using MATLAB software and results are provided in order to show the performance of this compensation technique in terms of harmonic distortion reduction and power-factor improvement.