جستجوی مقالات مرتبط با کلیدواژه « Voltage drop » در نشریات گروه « برق »

With the rise in the penetration of inverter based distributed energy sources, grid codes say that converters should not be disconnected during the fault. These sources should also help the grid by reactive power injection. Power system grids are resistive inductive and the converter may be unstable during the fault. Converters use phase locked loop (PLL) to synchronize with the grid. PLL is not able to be stable during severe voltage drop, so converters cannot ride through the fault and should be disconnected. In this paper a novel method based on virtual impedance is proposed to maintain the synchronization during severe voltage drop. This method needs grid impedance estimation and virtually connects the converter to a point that has a stronger connection. By this novel method, during voltage drop, the converter stays connected to the grid and injects reactive power. Simulation results in MATLAB verify the ability of proposed method in improving the transient stability of converter.

The increasing growth of load consumption and the increasing development of distribution networks have led the specialists of the electrical industry to take more accurate and suitable approaches into consideration to use the maximum capacity of existing networks efficiently. Optimal selection of location and capacity of distribution substations to reduce the cost and improve reliability and prevent the increase of losses for increasing the loadability capacity of the distribution network are among the most important measurements. In the present paper, the optimal placement of distribution transformers (quantity, installation location, optimal capacity, and service area) has been discussed due to the importance of optimization problems in distribution networks. Moreover, electric restrictions such as permitted voltage drop, permitted loading maximum capacity of transformers, permitted limits of loading for low-voltage line, feeding all the loads, and radial structure constraint have been considered, the efficient arrangement of the distribution network for the planning horizon of the desired year is probably to be achieved. Results of studies on the sample distribution network have been compared with the results of another algorithm, which appropriately indicates the efficiency of the proposed objective function.

One of the most critical and complex issues in long-term planning of distribution networks is the optimal placement of distribution transformers. In this paper, the optimal placement of distribution transformers was investigated based on a complete and multi-objective function. In the proposed method, location, optimal capacity, and the service area are determined by minimizing costs (investment, operation, reliability) and improving reliability and power quality parameters (voltage drop) due to electric restrictions (radial structure, voltage drop and equipment capacities). The planning of distribution networks is complicated due to the existence of numerous and multiple-criteria decision-making variables in objective functions; hence in this paper, the symbiotic organisms search (SOS) algorithm was used as a new heuristic optimization algorithm to solve the problem of long-term planning of distribution networks. The proposed method is tested on a real distribution network to evaluate the performance of the proposed algorithm,  Comparing the results of the proposed algorithm with the results of studies with genetic algorithms (GA), biogeography-based optimization (BBO) and imperialist competitive algorithm (ICA), indicates the performance and advantages of the proposed algorithm over other algorithms.