mohammad jafarifar

To evaluate the reliability of active distribution networks, there is a need to model distributed generation sources, mainly renewable ones. The traditional (common) reliability models are not able to take into account the intermittent and random nature of these energy sources, so the need for a new reliability model is necessary to model the production sources of this type of distribution network. In analytical methods, an analytical model of the network is prepared and the problem is solved mathematically; but with the complexity of the network, solving problems becomes very difficult and practically impossible. Therefore, in terms of the complexity of the structure and the variety of operating modes of active distribution networks, a simulation [Monte Carlo] method has been proposed to evaluate their reliability. In this method, all failure modes of network components are randomly classified and specified. On the other hand, by using the proposed model of reliability of DGs, the nature of randomness of these sources has been accurately considered in the simulation process. The simulation results of a sample active distribution network indicate that, with the introduction of microgrids, the reliability indicators of the network and its loads have improved, but the microgrid has had the greatest impact on the load indicators within the microgrid itself.

Helical magnetic flux compression generators (HFCG) and Two Stage-Helical flux compression generator (TS-HFCG) have been widely used to produce very high current pulses for many applications in recent decades. In order to accurate analysis and optimized design of these generators, it is necessary to calculate their electrical parameters. Among these electrical parameters, calculating the self and mutual inductances is important because it reduces the design and construction costs. In this paper, the calculation of self-inductance and mutual inductance profiles of TS-HFCGs is carried out using a three dimensional numerical method in the presence of an armature and its dynamic. For this purpose, the Maxwell equations governing the system are expressed in different parts, and then, using the utility software, the equations are solved and the inductances are obtained. In order to validate the results, a computer program is written in MATLAB based on the filamentary method and the results are compared.

In this paper, a new scheme for sensorless speed control of multi-phase induction machine under unbalanced supply conditions is proposed. There are many methods that use speed and flux estimators for sensorless control of induction machines, but the proposed scheme is based on current estimation without flux and speed estimation, in which the stator controlled voltages are applied to the machine so that the difference between the estimated stator currents and the real currents of the machine are forced to decay to zero. The simulation results in MATLAB/Simulink show that the speed of the induction machine in the start-up and speed reversal test follows the reference speed well. Also, in the load rejection test, by applying a mechanical load on the machine and then removing it, the proposed control method has the ability to control the speed of the machine well, and the performance of the machine will be stable under these conditions. Finally, a sensitivity analysis to the changes in the machine parameters shows that the proposed method has a relatively acceptable performance.

Multiphase (more than three phases) drives possess several advantages over conventional three-phase drives, such as reducing the amplitude and increasing the frequency of torque pulsations, reducing the rotor harmonic currents, reducing the current per phase without increasing the voltage per phase, lowering the dc-link current harmonics, and higher reliability. By increasing the number of phases it is also possible to increase the power /torque per ampere for the same volume machine. Another important feature of multi-phase drives is ensuring optimal and acceptable performance in unbalanced supply conditions due to interruption of one or even two phases, which has increased the acceptance of this type of drive in various industries. In this paper, speed control without mechanical sensor of six-phase induction machines in single-phase interruption conditions is presented using the second-order sliding mode control method. In this control method, the reference model theory is used to estimate the machine speed in order to improve the drive performance. The simulation results show that the method has an acceptable performance under unbalanced machine supply conditions and speed control will be performed well.