h. shahsavari

Distributed generators (DGs) facilitate minimizing a monetary objective for controlling overload or low-voltage obstacles. In conjunction with controlling such complications, a DG unit can be allocated for maximum reliability or efficiency. This study presents a new method based on a new index for locating and sizing DGs in electricity distribution systems. Stable node voltages which are known as power stability index (PSI) are considered in developing the index. An analytical method is applied in visualizing the effect of DG on losses, voltage profile, and voltage stability of the system. In this study, a new approach using co-evolutionary multi-swarm particle swarm optimization (CMPSO) algorithm is purposed for locating DGs in radial electrical distribution systems considering the uncertainty of solar power as well as load and wind power. In this paper, the optimal locations and sizes of DG units are calculated by considering the active power loss, reliability index, and PSI as objective functions. The presented algorithm is tested on 33-bus and 274-bus real distribution networks. The results of the simulation show the effectiveness of the proposed method.

In this paper, the theory and modeling of large scale photovoltaic (PV) in the power grid and its effect on power system stability are studied. In this work, the basic module, small signal modeling and mathematical analysis of the large scale PV jointed multi-machine are demonstrated. The principal portion of the paper is to reduce the low frequency fluctuations by tuned stabilizer in the attendance of the PV unit. In order to optimize the system performance, a novel optimal fuzzy based fractional order PID ( ) stabilizers are proposed to meliorate small signal stability of a power network connected PV unit. For optimizing the performance of the system,  is exploited by Gray Wolf Optimization (GWO) algorithm. In order of evaluation of the proposed stabilizers performance, two different types of controllers are compared, include optimal classic stabilizer and  based particle swarm optimization (PSO) algorithm. The superiority of  based GWO on improving small signal stability in the studied system, including large scale PV is shown via time-domain simulations.

Among the issues related to bridges distraction, a flood which causes scouring has been known as the main reason of bridges destruction. Therefore, finding an effective solution is vital for decreasing scouring depth. In this study, the effects of local roughness elements with different distance were investigated for a semicircular abutment under clear water scouring condition. Results showed that existence of roughness reduced the scouring process and reduced the final scour depth by 47%. There was a significant relationship between roughnesses function and the distance between them. So that the existence of an optimal value for the distance between the roughnesses increased the roughness function and decreased the scouring process. In addition, the study of vertical velocity profiles revealed that existence of positive vertical velocity in the hole located at upstream of the abutment and also negative velocities at higher depths were the indicator of downflows. As a result, these downflows lead to the formation of powerful vortexes inside the scouring hole and in front of the abutment. Comparison of the flow profile around the roughened abutment with the control abutment showed that velocity of downflow is significantly reduced for abutment with roughness. Moreover, the depth of scouring hole was reduced at behind of the abutment, due to the impact of roughness on vertical velocity profiles at downstream of abutment. So that, the velocity reduction of the vertical flow in the front and behind of the roughened abutment was to 0.13 U and 0.4 U (U approaching flow velocity), respectively.