Study On Guangdong Power Grid Transformer Neutral Point DC And Its Suppression

DC transmission technology as the main means of electricity long-distance conveying, which is gradually be taken seriously. On one hand, the widely used in DC power transmission system, but on the other hand, the current from grounding electrode of DC system do affect the stabilization of the power grid. Therefore, to ensure the normal operation of DC system and transformer is of great significance stable operation of power grids.Making the Guangdong power grid as the research object, this paper concerned about the influence factors and its variation characteristics of transformer neutral point current, and then discussed the combination of capacitance-type blocking device. In order to study the neutral point current of transformer, the paper analyzed in detail the mechanism of dc bias, and put forward reasonable blocking method to Guangdong power grid. Through regression analysis and simulation platform PSCAD/EMTDC, the paper analyzed the characteristics of DC magnetic bias.This paper proposed a simple model for calculating the neutral point current. In order to control the current effectively, three aspects had been used to analysis the characteristic, such as the transmission power and the structure of power grid and the blocking device. In addition, the research made the pearl river delta region in Guangdong power grid as an example, and calculated the value of neutral point current in a fast way.At present, Guangdong power grid using a blocking device operation strategy, which called neutral point current exceed principle. Such scheme not only in lower suppression efficiency and higher costs, but also complicates the grounding current and influences the network management. So this study proposed a new way to find out the better combination of blocking device, which used less cost to achieve better inhibitory effect. Capacitance-type blocking device has the characteristic of simple structure and significant effect, so this type of device is widely used in Guangdong power grid. Inspired by the genetic algorithm, this paper used particle swarm optimization algorithm to guide a more reasonable device combination. To make the standard particle swarm algorithm can solve the mixed integer programming problem, the crossover and mutation in genetic algorithm had been combined with the particle swarm algorithm, and conclusion showed that the improved algorithm can achieve the desire. Finally, the research made the Guangzhou network as the example, calculated the device combination strategy, and the simulation results of Math Lab showed that the method is effective.