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With the increasing integration of renewable energies into power grids, their control and power quality are becoming the main focus of many research efforts. In a grid-connected photovoltaic system, the control strategy is necessary to efficiently use the solar energy as well as to ensure high power quality. This paper presents a study on the robustness of a Fractional Order PI controller based on the Particle Swarm Optimization algorithm (PSO-FOPI) in a grid-connected PV system. The controller used was integrated into the inverter to apply voltage-oriented control (VOC). Fractional order controllers have an additional degree of freedom, so that a wider range of parameters is available to provide better control. Parameter optimization of the FOPI and classical PI controllers are performed using the PSO algorithm. The performance of the FOPI controller is compared with that of the classical PI controller. A complete study of the behavior of the grid connected PV system is tested using MATLAB/Simulink. The simulation results show the performance and efficiency of the PSO-FOPI controller compared to the classical PI controller in terms of rapidity, stability and precision, as well as the THD reduction of the current injected to the grid for any variation of solar irradiance.

FACTS devices installation is required to guarantee high energy quality and power system stability. The present paper tackles the problem of voltage control, reactive power and power factor improvement in an electric power network by one of the AC transmission devices (FACTS) of the static synchronous parallel compensator type (STATCOM), using serial multicellular converters with different levels (three to six levels). Such converters with special attention paid to the active balancing of capacitor voltages in order to generate good quality waveforms and improve the harmonic content of the output voltage. The controller's ability and functionality are evidenced through a detailed theoretical analysis. We elaborate the compensator's operating model by stating its equivalent electrical diagram representation. This is followed by a mathematical modeling and a control model based on phase shifted pulse width modulation (PS-PWM) technique to monitor reactive power flow inside the system and maintain the voltage at the common connection point (PCC) at a steady value. The proposed system simulation is carried out using Matlab Simulink environment. Finally, a presentation and a discussion of the obtained results are provided.

Numerous studies examine the electrical and mechanical, internal and exterior problems of induction motors separately. However, this type of machines is also susceptible to several combined faults which affect it at the same time. The aim of this work is to study firstly the effects of the mass imbalance with the supply voltage unbalance faults in a combined state, and specifically its effects on the stator currents (distortion of currents waveform and augmentation of current unbalance factor (CUF)). The findings of this research were derived from experimental tests, which enabled us to produce the combined voltage and mass imbalance fault intentionally. The second purpose of this paper is to identify these irregularities. In the field of induction motor fault diagnosis, the stator current analysis techniques have shown to be quite successful and have gained widespread use. Therefore, we used the well-known method motor current signature analysis (MCSA). In addition, we have strengthened the research by using spectral analysis on the Park's components (Id and Iq). The obtained results demonstrate the efficacy of analyzing stator currents and Park components spectra (particularly the direct Park component (Id)) for detecting this kind of electrical and mechanical combined defects