Rita Mbayed

Power operating domain of a cascaded doubly fed induction machine

The paper deals with the steady state operating limits of a cascaded doubly fed induction machine (CDFIM) in terms of active and reactive powers. An analytic method is suggested to derive the power region, in which the machine can operate safely without exceeding its rated parameters. The proposed steady-state analytical study has been thoroughly validated by simulations using an elaborated model of the CDFIM implemented on Matlab-Simulink. It is shown that the power capability is subject to several limitations. For a limited speed range the reactive power consumption and generation are determined by the stators current maximum values. The study is further extended to illustrate the effect of the slip range and the terminal voltage on the power limit curves.

New voltage sensorless approach for maximum constant power tracking of WECS based on a cascaded DFIG

The paper proposes a new control strategy of a grid connected variable speed wind turbine (WT), based on a cascaded doubly fed induction generator (CDFIG). The generating plant is carried to extract the maximum power relative to the predicted mean wind speed, thus eliminating the power fluctuations associated to high frequencies component. Moreover the system attempts to adjust the power factor of the generated power according to grid code requirements. This can be achieved by means of a bidirectional back to back PWM converter. A virtual flux oriented vector control is applied for the decoupled regulation of active and reactive powers, leading to grid voltage sensorless operation. The suggested method ensures high efficiency and enhances the energy quality by feeding constant power into the grid, regardless wind fluctuations.

Loop-shaping H∞ control for a doubly fed induction motor

This paper deals with a doubly fed induction machine (DFIM) where both sides are supplied by two PWM inverters. The study consists in elaborating a robust vector control of the machine by the loop- shaping Hinfin approach. The Hinfin loop-shaping theory is presented in brief; then it is applied to the control of the DFIM. The simulation results prove that the implementation of the Hinfin controllers for currents, fluxes and speed loops leads to excellent robustness in stability and good dynamic performance even with large electrical and mechanical parameters uncertainty.

Modeling and control of a stand alone cascaded doubly fed induction generator supplying an isolated load

The modeling and control of a variable speed cascaded doubly fed induction generator feeding an isolated grid in aircraft application is presented. Despite the complexity of the generator an efficient controller can be elaborated based on the theory of a unified reference frame vector representation. An indirect decoupled vector control of terminal voltage is implemented using field orientation techniques. The controller insures good tracking of voltage magnitude and frequency regardless load and speed variations.

New approach for maximum power tracking of a variable speed WT at constant power generation, under normal grid conditions

In this paper, we suggest a new control approach for maximum power extraction applied to a variable speed Wind Turbine (WT). The proposed method aims to generate a constant maximum power defined over a given interval. The power set point is derived based on the mean wind speed predicted value. Since the wind speed turbulence component does not contribute to the average produced energy but only affects the power quality, the averaging period is chosen in order to eliminate the power fluctuation generated by this high frequencies component. This technique insures a better energy quality and retains a high system efficiency.

Comparison of the water heating technique's impact on the sizing of a standalone PV-battery backup system assisting an intermittent primary energy source

This paper is a comparative study of the effect of various water heating techniques on the sizing of a PV-battery backup system for an intermittent grid supply. The optimal water heating configuration is found based on the smallest sizing of the backup system. Four popular water heating techniques are modeled and compared; the electric water heater, hybrid solar electric water heater, boiler water heater and the hybrid solar boiler water heater. A high energy consumption residential application is considered, realistic constraints are applied, and a detailed economic study is conducted in order to accurately quantify the advantages and consequences of each installed water heating technique.

Control of a cascaded doubly fed induction generator supplying an isolated DC grid

This paper presents the cascaded doubly fed induction generator as a potential candidate machine for electrical power generation in embedded aircraft applications. HVDC network is considered. The machine is connected to a diode bridge rectifier. The set operates as a stand alone DC generator connected to an isolated load. A new decoupled vector control is proposed to regulate the DC bus voltage. The controller aims to retain a constant output voltage regardless load and speed variations.