Thèses de Doctorat et Mémoires de Magister
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Item Protection scheme enhancement of synchronous generator(Université M'Hamed Bougara : Institut de génie électrique et électronique, 2021) Mati, Ayache; Bentarzi, Hamid(Directeur de thèse)Synchronous generator is the most important element of a power system and its fast and reliable protection is crucial. One of the most abnormal conditions in a generator is loss of excitation (LOE) which is harmful to both the generator and the power system. This condition should be detected and the generator isolated from the system to avoid generator damage as well as power system instability. This thesis presents a study and comparison of the two conventional LOE protection schemes, negative-offset and positive-offset mho element under different conditions. The results show that the two schemes can detect LOE fault under total or partial LOE conditions, however in terms of speed (fault detection time) the positive offset scheme is faster than the negative offset scheme under all loading conditions. Besides, the two LOE protection schemes are reliable and do not operate under power swing disturbances caused by any type of external faults. Moreover, the impact of the static synchronous compensator (STATCOM) on the positive-offset mho element LOE protection scheme is investigated. The obtained results show that the operation of the positive-offset protection scheme takes more time under the integration of STATCOM in the transmission line. Finally, to reduce this delay time, an enhanced method based on phasor measurement unit (PMU) is proposed. The simulation results show that the new developed method improves the operation of the positive offset mho element LOE protection by reducing the delay time that may be due to the presence of STATCOMItem Feedback linearization of mimo systems described by a nonlinear state space equation(Université M'Hamed Bougara : Institut de génie électrique et électronique, 2021) Kessal, Farida; Bentarzi, Hamid(Directeur de thèse)The idea of feedback linearization is to cancel the nonlinearities and imposing the desired linear dynamics via change of coordinates and feedback so that the linear control techniques can be applied. In this thesis feedback linearization is applied to a class of multivariable nonlinear systems; where the number of inputs divides exactly the number of state. The proposed method consists in converting a nonlinear multivariable system into block controller companion form that is suitable for block pole assignment which amounts to eigenstructure assignment. Necessary and sufficient conditions for input-state linearization have been developed. Comparison study has been achieved between the proposed approach and the feedback linearization for general form of multivariable nonlinear system. To verify the validity and effectiveness of the suggested method, a two-link robot manipulator has been implemented. When a nonlinear system presents a non-involutive property, the approximate feedback linearization is required. The idea of the proposed method consists in representing the original nonlinear system into a state-dependent coefficient form then applying block similarity transformations that allow getting the linearized system in block companion form. Examples have been used to illustrate the application and show the effectiveness of the given approachItem Oscillation damping improvement using PMU based PSS in power system(Université M'Hamed Bougara : Institut de génie électrique et électronique, 2021) Bousaadia, Baadji; Bentarzi, Hamid(Directeur de thèse)The interconnection of power systems and the increase of power transfer are required to meet the increasing demand of electrical energy. These requirements drive the modern power systems closer to their limits of operation. Consequently, low frequency oscillations may arise in systems not affected previously and become a major source of systems instability and limitation factor of power exchange over long distances. One method of mitigation of those oscillations relies on power system stabilizers (PSSs) that can provide effective damping to local oscillation modes by using locally measured signals. However, they lack observability of inter-area modes, which results of poor damping for those modes. In this thesis, a wide area power system stabilizers (WAPSSs), able to effectively damp out inter-area oscillations in large power systems, is adopted. The proposed approach relies on the development of phasor measurement units (PMUs), which provide remote signals as inputs for WAPSSs for real-time implementation. The effectiveness of the proposed approach depends on many considerations. The first step is the selection of suitable control locations and remote signals with high observability to the targeted inter-area modes. To face this requirement, geometric measures of observability and controllability is adopted. The second crucial step is the optimal tuning of WAPSS to achieve adequate damping. A novel metaheuristic algorithm, comprehensive learning bat algorithm (CLBAT), is employed for the tuning process and compared with state of the art metaheuristic algorithms. Finally, the time delays associated with the global signals can deteriorate the performance of the proposed WAPSSs. Thereby a time delay compensators are proposed compensate time delays in wide area measurements based control. The performance of these WAPSSs has been evaluated on the New England/ New York and Two area four machine multimachine systems via eigenvalue analysis, and nonlinear time domain simulationsItem Reliability aware design of integrated circuits(Université M'Hamed Bougara : Institut de génie électrique et électronique, 2021) Chenouf, Amel; Bentarzi, Hamid(Directeur de thèse)The striking advances in both computer-aided integrated circuit design and manufacturing technologies have paved the way for designing and manufacturing highly complex, high-performance chips integrating more than 100 million transistors into a few square millimeters of silicon. However, this high density has brought with it more challenges for IC designers in terms of their circuits reliability sign-off. In fact, due to the aggressive scaling, and to wear out effects, the electrical parameters of semiconductor devices are shifting over time, causing for ICs the failure to meet the specifications for which they were designed. However, a technology-based solution is not always feasible, mainly because semiconductor engineers usually focus on developing smaller, faster, and less energy-intensive transistors. This compels designers to moderate this degradation and to improve the lifetime of their circuits during the design phase. A simulation of aging becomes therefore essential to predict the performance degradation of the ICs due to temporal variations. Moreover, the introduction of new design techniques which consider reliability as a design constraint as important as speed, area, and power consumption, becomes more than necessary to warranty delivering reliable circuits and systems by adopting design for reliability (DFR) concept. In this prospect, we propose, on one hand, to migrate reliability analysis from device-level to a higher level of abstraction. This allows a better assessment of the induced degradation on the circuits’ performance. On the other hand, we propose a DFR approach to deign reliable circuits. For this PhD thesis we choose, to deal with NBTI, which is one of the most wear-out mechanisms shrinking the lifetime of deep submicron ICs. We present our NBTI circuit-level characterisation results, the implementation of our NBTI model on a commercial simulator. On the other hand, we present an NBTI mitigation approach based on transistor sizing we propose for designing robust 6T-SRAM cells