The greatest requirement for Tunisian grid connections is low voltage ride through (LVRT). In fact, the network voltage generally results in a discrepancy between the generated active power and that which is delivered. This study was carried out to enhance the quality of the power injected into the grid by means of LVRT capability in Tunisian wind turbines using a permanent magnet synchronous generator (PMSG) controlled by the sliding mode control (SMC) approach based on direct power control (DPC) using space vector modulation (SVM). This approach was applied in order to control the active and reactive powers produced by the wind energy conversion system (WECS) and injected into the grid. Results obtained in MATLAB/Simulink simulations showed the efficiency of the introduced control strategy. An implementation in real time, using a dSpace1104 control board, was presented to illustrate the feasibility of the proposed control scheme and its effectiveness under fault conditions.

This article deals with the direct power control strategy applied for a grid-connected variable speed wind turbine based on doubly fed induction generator. The proposed method is based on a stator flux estimation algorithm which allows to control the rotor-side converter of the doubly fed induction generator. Several methods of stator flux estimation are based on the integration of the stator back electromotive force signal. However, in practice, the pure integration can cause various problems due to noises, stator resistance uncertainty, unknown initial conditions and measurement errors. Several algorithms, reported in the literature and used to estimate machine stator fluxes, are reviewed and compared. Particular attention is drawn to the low-pass filter–based algorithms that show good performances. In this article, the novelty of the proposed approach is the development of the direct power control–based stator flux estimation method with a low-pass filter. Theoretical analysis and implementation procedures of the proposed method are developed in detail. Simulation results of a variable speed wind turbine based on doubly fed induction generator are performed in MATLAB/Simulink software in order to evaluate the dynamic performances of the proposed control method under wind speed variations. The adopted control strategy is implemented using dSPACE 1104 board and tested for a wind turbine emulator. Experimental results show the effectiveness and the originality of the proposed control strategy.

This article deals with the control techniques of a low-voltage grid-connected to wind power conversion system based on a permanent magnet synchronous generator (PMSG) using an indirect matrix converter (IMC). Details of the proposed strategies for both the rectifier and inverter stages of the IMC are presented. Thus, a rectifier control strategy based on voltage-oriented control using space vector modulation is proposed. In addition, the control objective of the direct power control (DPC) inverter is the regulation of the active powers of the PMSG according to references established on the basis of the maximum power point tracker (MPPT) of the wind turbine, and also a good tracking of the output reactive power to its reference ensures unit power factor (UPF). A numerical simulation investigation is conducted to investigate the fast-dynamic performance of the proposed control systems during the wind speed variation. The obtained results in simulation are then complemented with tests in laboratory environment, the DPC control system is implemented on a dSpace DS1104 real time board. Selective experimental results are presented using a laboratory prototype of the wind energy conversion system to demonstrate the resulting improvements of the developed system. The results achieved have been clearly responded to the follow-up of references even under fluctuating wind conditions, and show promising relevance of the proposed method.

This article deals with the power flow control in a hybrid power system, which is composed of a fuel cell, photovoltaic system and a super capacitor. The super capacitor has been employed with an aim to ameliorate the performance of the hybrid power system. In addition, it takes into account the energy fluctuations of photovoltaic energy sources and the slow dynamic of the fuel cell. Each source is connected to a DC/DC converter and their outputs are connected to a common DC-link and they supply a DC load. Furthermore, an energy management algorithm has been carried out in order to commonly share the power between the sources and the load. The proposed energy management method shows its flexibility, and an efficient energy conditioning between different sources is guaranteed in case of multi-source system. The main originality of this work lies in the use of AC-link partial resonant DC–AC converter topology to interface hybrid system and to inject the excess of energy to the grid. In this article, the system description, the control and the modeling of DC/DC converters and the AC-link converter are provided. Finally, simulations under Matlab/Simulink are shown in order to validate the effectiveness of the proposed control strategy and the energy management algorithm. An implementation on real-time using dSpace 1104 is presented to illustrate the feasibility of the proposed control strategy.