فصلنامه روشهای هوشمند در صنعت برق
پیاپی 32 (زمستان 1396)

Recent developments in renewable energy sources has created demands for high step-up and high efficiency DC-DC converters. This demands are fulfilled basically through the use of high frequency transformer to achieve the required and desired gain. Power electronics solutions based on multi-converter structures provides economic methods for input and output power by combining a number of components. In this paper some of structures reviewed that have been proposed to achieve a high step-up converter and the advantages and disadvantages of these converters are discussed. The proposed converter is provided in order to reduce the voltage stress of high step-up converters based on coupled inductor and passive clamping circuit. The voltage stress of switches in the proposed converter is less than a simple boost converter also in this structure with using passive clamping circuit the oscillation of both sides of the switches is a little clamped and finally by using this technique it can achieve high gain by selecting the appropriate duty cycle. In this paper to review the principle of operation of the proposed converter theoretical analysis are provided and to verify the results of theoretical analysis of the proposed converter is given with its PSPICE simulation.

Electrical and mechanical benefits, simple manufacturing and maintenance of switched reluctance motor make it suitable in industrial and home applications, but the most important drawbacks of switched reluctance motor are discontinuous torque and no self-starting in some rotor positions. In this paper a novel rotor structure is presented and optimized in order to increase positive torque region and eliminate dead-zone in high loads. The torque produced in this proposed SRM is divided in two regions and overlapped in two phases periodically. In order to find the best output character and optimal design, two factors, position and angle of cut edge are optimized. To verify the proposed rotor, torque characteristic, flux path and torque ripple has been analyzed by finite element method and compared with conventional 4/2 switched reluctance motor. The proposed motor has a continuous torque characteristic.

In this paper, a new soft switching high step up converter is introduced which its auxiliary circuit does not have any extra switch. Therefore, it no needs extra driver circuit and control circuit is simple. Also the energy in auxiliary circuit transfers to the output. The auxiliary circuit provides zero current condition for turns on and zero voltage condition for turns off instants of the switch. In addition all diodes turn off under ZCS condition and reveres recovery problem don’t exist in them. One of the advantages of the proposed converter is the reduction of the voltage stress across the switch due to its high voltage gain. Also, the auxiliary circuit has a low number of elements; therefore, high conduction losses do not impose on the converter. The coupling inductors in the auxiliary circuit have low values, so the volumes and parasitic magnitudes do not increase. To verify theoretical analysis a prototype of the proposed converter is implemented.

Nowadays, service-oriented systems according to possibility of using in heterogeneous distributed environments and being independent of the specific technology, also with the existence of large-scale dynamic system with changeable requirements, are highly regarded. Cloud services are one of the implementation methods of service-oriented concepts. Increasing the tendency of users to use cloud computing, encourages service vendors to provide services with different non-functionality features. Mostly single services couldn’t satisfy users’ requirements, so it’s necessary to compose some services to achieve the demand service. With the increasing of service providers, also services in the internet service pools, selecting the optimal service from a set of functionality equivalent candidates which are differ in QoS, becomes an important NP-Hard research problem. Therefore increasing the quality of composite services is a vital challenge and since the quality of cloud composite services derived from previous approaches can still be increased, in this research, we have tried to increase the quality of cloud composite services using the Symbiotic Organism Search Algorithm. Simulations are conducted in Matlab environment and the results are compared to three famous algorithms including GA, ACO and PSO. The comparisons demonstrate the remarkable superiority of SOS in result's quality, stability and scalability, also 13% improvement.

Today, optimization in power systems is an unavoidable necessity. Energy intensity reduction in electrical devices and enhancement of their efficiency and performance, electricity loss reduction and voltage profile improvement of the power grid are some instances of optimization usage in power systems. Refrigerated systems, such as refrigerators, can, in addition to exploiting PV systems in a power grid, be part of the supply and demand of electrical energy, so that they store energy as energy and, in the necessary conditions, allow Energy to injecting into the power grid by a photovoltaic system. In this paper, the design and construction of a photovoltaic refrigeration system connected to the network and its optimal performance is discussed. The objective cost and refrigerating temperature functions are considered as two main goals and the final answer is chosen by using the non-dominated sorting genetic optimization algorithm and then using the weighted sum model method. The simulation results with MATLAB software as well as the results of implementing the proposed system's hardware system in the project verify both the performance and the optimal performance of the proposed system.

This paper presents an adaptive state feedback control scheme for a class of nonlinear systems with unknown parameters, variable control gains and in the presence of unknown time varying actuator failures. The designed controller compensates unknown loss of effectiveness failures as well as unknown time varying stuck failures in actuators. The considered actuator failure can cover most failures that may occur in actuators of the practical systems. The proposed adaptive controller is constructed based on a backstepping design method. Appropriate Lyapunov-Krasovskii functionals are introduced to design new adaptive laws to compensate the unknown actuator failures and unknown parameters. The offered method ensures the asymptotic output tracking and the boundedness of all the closed-loop signals. The proposed design approach is employed for a wing rock control of an aircraft in the presence of time varying actuator failures. The simulation results verify the effectiveness and correctness of the proposed adaptive control method.