Research On Detection Method And Control Of DC Microgrid Voltage Quality

In recent years,fossil energy has become increasingly depleted,and distributed power sources have been developed and utilized on a large scale.Due to the uncertainty of the distributed power's output power,the pressure on the traditional distribution network is increasing.With the rapid development of power electronic devices and the increasing number of DC equipment,the DC power supply system has returned to people's vision.The DC microgrid has become a new trend to solve a series of problems in the traditional distribution network because of its convenient access to distributed power sources and DC loads and its high reliability.At the same time,the increasing number of non-linear loads and sensitive loads make power quality issues an important research direction for power systems.In AC systems,the issue of power quality has attracted a lot of attention.In the DC microgrid,the problem of power quality cannot be ignored.Firstly in this paper,by comparing the typical structure of DC distribution network and AC microgrid,and combining the application scenarios of DC microgrid,the typical topology of DC microgrid is determined as a radial single bus structure.The basic components,voltage levels and system parameters of the DC microgrid were discussed,and the connection and control methods of each component of the microgrid were discussed.The Simulink simulation software was used to establish the DC microgrid model including DC load,AC load,distributed power and energy storage devices.Because there is no problem of reactive power and frequency in the DC microgrid,the power quality is concentrated on the voltage quality.In this paper,the Simulink DC microgrid model is used to set up a variety of working conditions for simulation,combined with formula deduction to analyze the mechanism of transient and steady-state voltage quality.Use the mature method of the AC system to study the detection method of voltage sag and voltage fluctuation to meet the real-time and accuracy requirements of the algorithm.The method of combining windowed Fourier transform and spectral line interpolation calculation is used to detect voltage harmonics and interharmonics.Carrying out example analysis through simulation to verify the feasibility of the detection method.Finally,the control method of DC microgrid voltage quality is discussed.A control strategy for energy storage device to improve voltage fluctuation and sag is proposed.The improvement effect of this control strategy is verified by simulation:For the voltage quality phenomenon caused by power imbalance,a good improvement effect can be achieved by this control strategy.For voltage sags and short-term interruptions caused by faults in the microgrid,the faults are first removed using a relay protection device,and then the energy storage device is put into operation.For the suppression of the voltage harmonics and interharmonics of the DC micro-grid bus,the method of increasing the number of converter groups,using flat wave reactors and DC active power filters is adopted.By comparing the simulation results,it is found that these methods can achieve good results.In short,the phenomena mining analysis,detection method research and control method research on the DC microgrid voltage quality are beneficial to promote the research of DC microgrid voltage quality.It provides scientific theoretical.reference and method support for the construction and operation of DC microgrid in the future.