Research On Impedance Matching Method Of DC Filter In Distribution Network

The DC distribution network has become an important trend in the future with its significant advantages,but a large number of non-ideal access terminals may cause harmonics which flow into the power grid to constitute a hazard.The change of the grid load will affect the filtering performance of the DC filter in the distribution network.When the load changes,the harmonics after the filter flowing into the system will be amplified,and harmonic pollution of the power grid will be aggravated.This paper toke DC distribution network as the research object,and the related research on DC filter impedance matching method was carried out.This paper systematically analyzed the DC distribution network,and proposed a DC switching structure based on phased-controlled thyristors connected in parallel.Based on the MATLAB platform,a 10 kV radiating distribution network simulation model was established.The DC harmonic content and characteristic were obtained through simulation.The harmonic suppression method was analyzed to lay a foundation for the subsequent filter research.In order to study the impedance matching characteristics of DC filter,this paper analyzed the working principle of DC active filter,traditional passive filter and elliptic function filter,and determined the design method of various filters.Then,filter parameters were designed and optimized respectively,and the filtered voltage waveform and harmonic content were obtained through simulation.It was proved that the filter was effective for harmonic suppression.By comparison,the conclusion that the elliptic function filter impedance matching performance is optimal was obtained.In order to investigate the stability of the elliptic function filter,the system transfer function was deduced and the sensitivity of each component was calculated.The obtained results proved the filter tolerance ability.Considering the deviation of the filter parameters in the actual operating conditions,the deviation of ±5% was used as an example to simulate different trigger angles and different impedance conditions.The result showed that the filtering effect was good when the trigger angle increases and the harmonic suppression ability of each parameter filter does not change when the load changes,indicating that the elliptic function filter can still maintain a good impedance matching performance when the parameters are changed within a certain range,which proves low sensitivity and high stability.Finally,a low-voltage distribution network simulation model was built,and the hardware system connection of the analog low-voltage distribution network was completed.For the specific model,the filter parameters were designed,and the filter improvement measures were proposed,and the response time was shortened.Through the simulation and experiment of the two cases with different capacity and load jump of the distribution network,the validity of the elliptic function filter algorithm for the harmonic suppression of DC distribution network and the good impedance matching were verified,and the correctness and feasibility of the method was verified.In this paper,the impedance matching performance of DC filter was studied and verified through the combination of simulation and experiment.This provides a theoretical basis for the future construction of DC distribution network and the improvement of filter performance.