Abstract:Voltage flicker and harmonics are the power quality problems which are introduced to the power system as a result of nonlinear and stochastic behavior of the arc furnace operation. To analyze harmonic and flicker generated by an arc furnace, accurate arc furnace models are needed. In this paper, different arc furnace models with different level of complexity are reviewed.In the first part of this paper a new developed time domain static model based on a piece-wise linear approximation of the V-I characteristics of the arc furnace is presented. While static arc models are useful for harmonic studies, dynamic models are useful for power quality studies specially the study of voltage flicker.In the second part of the paper, dynamic model for an arc furnace using MATLAB (Simulink) is presented. In addition to this, the novelty of this simulation technique lies in the fact that the variation of power transmitted to the load by the arc furnace during the cycle of operation is considered, thus making the proposed model more accurate and dependent on the operating conditions of the load.Finally recommendations are made for the application of some of these models and the accuracy of the presented model to other models from the practical point of view by using MATLAB is shown.
Abstract. This paper proposes a new unified active filter to alleviate instantaneous unwanted oscillating powers as they may lead to frequency variations in weak systems. First, the paper presents negative impacts of capacitive loads on the shunt active power filter performance in compensation of instantaneous oscillating real power. Secondly, an advanced universal power quality conditioning system (AUPQS) for three-phase/four-wire systems under non-ideal waveforms is introduced. By considering the suggested compensation algorithm, the AUPQS is able to extremely suppress instantaneous oscillating powers caused by distorted-unbalanced load-terminal voltages. Moreover, an independent single-phase converter is suggested at the load-end in order to regulate the DC-link voltage. Therefore, the instantaneous oscillating powers perfectly suppress and thus, the source-end three-phase currents will be purely sinusoidal. The suggested AUPQS is used to stabilize micro grid frequency. The effectiveness and flexibility of the proposed AUPQS are confirmed by Matlab/ Simulink simulations.
Hitherto, in the field of aerospace science and industry, some acceptable results from control behavior of human operator (pilot), are caught using usual methods. However, very fewer research, has been done based on personal characteristics. The performed investigations, show that many of happened faults (especially in helicopter), would result to the loss of natural behavior of system, and eventually some fatal accidents. Therefore, development of tools of assessment of pilot in this dynamical system, is one of the vital necessities. The tools of management of system, should be such that, can show the fault. The object of this paper is assessment of the modelled pilot in a simulator, in presence of standard fly inputs. For this purpose the performance of the pilot for collective and cyclic control of the helicopter, is investigated. The used methods are based on mathematical models and by bond graph modeling method. The existence of uncertainties in the simulator system and the modeled pilot's behavior, causes creation of fault threshold, for human behavior of pilot. By having these fault thresholds, the improper actions of the pilot, cause creation of behavioral reminders, which can perform the assessment of the pilot. By other speech, using fault detection and isolation (FDI), by bond graph method in state space, the assessment is performed and a non-zero reminder shows existence of fault in the system.
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