فصلنامه روشهای هوشمند در صنعت برق
پیاپی 28 (زمستان 1395)

One of the most prominent challenges in meeting the demand is the scarcity of radio resources. Cognitive radio is one of the techniques has been proposed for efficiently utilizing the radio resources. In Cognitive Radio CR) networks, the CR users have opportunities to access the licensed spectrum bands assigned to the primary users (PUs). Since the PUs have priorities to use the bands, the CR users are not allowed to generate unacceptable interference to them. In this paper, we investigate power allocation schemes for CR networks with two users where one users uses direct transmission and the other uses AF relay-aided transmissions. We first formulate an overall rate optimization problem with interference constraints to the PU and peak power constraints at each node and obtain solutions by theoretical analysis. We also simulate the solution base on different location of the relay and different location of the PU network.we compare the results with equal power allocation

In this paper a new soft switching boost-flyback converter is introduced to eliminate conventional boost-flyback converter problems in the high voltage applications. The main application of this converter is conction of PV system to the power system. In the proposed converter not only the operating duty cycles proper in high voltage gains but also the switch voltage stress is lower than output voltage. Also, in the proposed converter any auxiliary switch or magnetic core has not been used so the number of converter components has not increased much in comparison with the conventional boost-flyback converter. The operation principles of the proposed converter and its theoretical operation waveforms is presented. In order to justify the theoretical analysis, a prototype of the proposed converter is designed, simulated and experimentally implemented. The simulation and practical results are presented for a 100w boost-flyback converter with input voltage of 40V and output voltage of 400V.

In this paper a new idea of direct three-phase to single-phase Z-source matrix converter (impedance-source matrix converter) applicable in stand-alone wind turbine is introduced. In the direct Z-source matrix converter amplitude of output voltage and frequency regulation are of importance to control system. In wind turbines, input voltage and frequency are usually changing due to wind speed variation that these alterations could be easily regulated by means of a direct Z-source matrix converter. A scheme is also offered to control the proposed direct three-phase to single-phase Z-source matrix converter. the control strategy would be able to adjust the output voltage and frequency at desired value as well as producing low THD (total harmonic distortion) at the output voltage. The proposed structure and the control methodology are simulated using matlab simulink software and results are investigated and discussed to confirm the performance of the direct Z-source matrix converter in wind turbine.

sun is of the clean and cheapest sources of energy. Charging slight energy to electricity is carried out by PV modules. Since most electric consumers need Ac input voltage, the PV modules output voltage should be changed into Ac form. But, the voltage level of PV modules is much lower than the voltage needed in input stage of inverters. Because of large voltage level. Difference it is not possible to use the basic boost and buck-boost converters. The basic boost and buck-boost converters definitely can not be used in this applications, for, they will face extreme drop in efficiency in duty cycles closer to unity.
In this paper The proposed converter is presented in order to decrease the voltage stress of coupled inductors based high step-up converters. The voltage stress in the proposed converter is lower than the high step-up boost converter with coupled inductors in identical condition. Also, soft switching condition for switches and diodes is realized by active clamp circuit, and with this technique and proper selection of duty cycle, large gain and high efficiency could be achieved ultimately. . In this paper theoretical analysis is used for analyzing the performance of the proposed converters, and in order to verify the theoretical analysis, simulated results from pspice software is provides.

In order to quality service improvement, digital video broadcasting terrestrial should increase both channel capacity and also data rate. The system should be stable against fading. To achieve this aim, using multiple input multiple output which is equipped by dual polar antennas with low correlation is practical. However, using polar antennas lead to interference creation caused by cross polarization. This issue bring the decrease of both data rate and transmit capacity. To decrease the influence of depolarization, applying successive interference cancellation (SIC) is very effective. In this paper, a new detection algorithm based on SIC detection is proposed. The main characteristics of this algorithm is changing in the SIC detection nulling. This article also shows that, in environmental with high fading, in contrast to other detection method like ZF-SIC and MMSE-SIC, bit error ratio performance versus SNR is improved in new proposed detection method. ok . ok. ok .ok .ok .ok .ok .ok

this paper has scrutinized an effective approach regarding to how to elicit double quasi-sinusoidal waveform with orthogonal angles that can be applicable for two-phase induction motors. Hither, to be more precisely declared that a switching strategy is proposed so that the provided voltages by Matrix Converter (MC) i.e., A and B phases have 90⁰ difference with each other. This switching strategy assists two-phase induction motors aimed at operating in appropriate state. As the created frequency in an important item for this motor, matrix converter can also undertake this function. It is worth mentioning that, the switching is somehow performed until bio-directional switches couldn’t be simultaneously triggered and withal taken place in the accurate switching order. Its related circuit in order to producing appropriate current and voltage has been tested considering MATLAB Simulink and experiment. The simulation result is extracted with respect to inductive and resistive load. Meantime, PWM method is carried out to extract experimental results that clearly show its effectual performance.