Mohamed Ben Ali Kammoun

Behaviour assessment of DFIG based wind turbine generator while coupling to the grid using a new and practical connection technique

This paper proposes an easy, new and practical technique for connecting a Doubly Fed Induction Generator (DFIG) based Wind Turbine Generator (WTG) to the distribution grid. In fact, a DFIG can be assimilated to a synchronous generator except for an AC supply in the rotor windings. Therefore, eventually, the DFIG can be coupled to the grid in a similar way to the synchronous machine through rotor windings supply control. Actually, this technique is found practical, as it does not require any type of control loops, but in contrast, the DFIG is ready for any type of control (Flux Oriented Control, Direct Torque Control...) once starting is completed with this technique. In addition to steps of this procedure, a state model of the system is given including two DFIG models (before and after connection). These models were simulated on a 300 kW wind generation system using Matlab/SIMULINK environment. According to the simulation results, a behaviour assessment of the generator before, during and after connection is given so to evince benefits and drawbacks of this procedure.

Three-phase self-excited induction generator analysis in stand-alone mode

Currently, to supply power for a modern life, many researchs are being directed at alternative energy sources. One of the most promising sources is wind energy. In isolated systems, squirrel cage induction generators with capacitor excitation, known as self-excited induction generators (SEIG), are very popular. This paper presents a steady state analysis of three-phase self-excited induction generator with parallel compensation. An arrangement using a variable speed drive and a 4.4 KW induction machine excited with a capacitor bank to supply resistive or resistive-inductive loads was the subject of investigation. A new method, for determining the minimum and maximum capacities ensuring the performance of self-excited induction generator by a simple mathematical model, is presented.

A new five parameters estimation method for two-diode model of PV module

A new method for the estimation of the five parameters of two-diode PV model is presented in this paper. This method allows obtaining dynamic series and shunt resistances versus climatic condition changes. Compared with five parameter estimation method based on STC condition, this method shows to be more effective with the variation of the irradiance and temperature of the PV module. Simulated I-V curves are compared to experimental characteristics for a mono-crystalline PV module under different temperature and irradiance. The results reported in this paper confirm that the presented algorithm performs better than the STC one. Finally some considerations about the impact of the variations of the series resistances on the PV module performance are drawn.

Optimal tuning of power system stabilizer using genetic algorithm to improve power system stability

In the few past decades, power system stabilizers play an important role in power systems by ensuring the stability of the single machine infinite bus power system. In this context, several researchers have devoted their work to design the structure of the PSS and to optimize its parameters. In this paper, the structure of the integrated PSS is described. In order to optimize the PSS parameters, the genetic algorithm approach is proposed, developed and used. The performance of the proposed optimization method was evaluated by applying a short circuit default on a single machine infinite bus power system. Different results demonstrated that the genetic algorithm is able to find the optimal parameters of the PSS ensuring the stability of the power system.

A comparative study of PI and Sliding mode controllers for autonomous wind energy conversion system based on DFIG

Nowadays, the electricity demand in remote areas is increasing. Among a variety kinds of renewable energy sources, wind energy is very used. This type of energy presents a realistic alternative for power production. Therefore, to ensure optimal use of this energy, different control strategies are well studied in the literature. In this work, an autonomous wind energy conversion system based on a double fed induction generator (DFIG) is studied and modeled. The main goal of this work is to maintain the stator voltage and frequency to their reference values (220V, 50Hz) under variable mechanical speed and load variations. To achieve this purpose, two types of controllers are studied and compared: The vector control (PI) and the sliding mode controllers. Simulation results demonstrate the high precision and the robustness of the sliding mode controller compared with the vector controller (PI) mainly in case of wind speed variations and load demand changes.

Transient stability improvement for grid connected, fixed speed, pitch controlled wind turbine generator

The rapid growth of wind energy need requires more efficiency in the produced energy. For fixed speed wind turbines, the connection of its squirrel cage induction generator to the grid leads to inrush current which can reach 1.5 p.u. up to 2.5 p.u. in higher wind speed. We propose in this paper a new soft-starting of squirrel cage induction generator based wind turbine connected to the grid. Our strategy overcomes such transient instability problems and pinpoints rapidly synchronous speed for each wind speed acting on pitch angle.

Fuzzy maximum power extraction control for a photovoltaic water pumping system

AC loads present a delicate matter for photovoltaic systems, and this is because of the photovoltaic panels operating point, which moves randomly according to irradiance changes; in this case, almost of photovoltaic water pumping systems use a DC-DC converter to ensure either the maximum power extracted from PV panel or the load needs. For AC motor pumps, an inverter must follow this chopper. Adding more components to the pumping system leads to reduce its yield. That is why we suggest a new photovoltaic water pumping strategy in which the DC-DC converter is discarded. The idea is to provide cheaper and more efficient, relatively small, water pumping station, dedicated for remote areas. The control strategy imposes the operating regime for the scalar controlled single-phase induction motor pump by imposing the operating frequency, e.g., its absorbed power near the MPP operating point of the PV panel and this according to fuzzy logic algorithm. For this, a modelling of all system components is detailed. Simulation results show the effectiveness of the proposed control strategy.