| With the use of new energy equipment and the expansion of power grid scale,the shortcomings of traditional AC distribution system in transmission power,system loss and reliability are becoming increasingly prominent.DC distribution network has become a new development trend with the advantages of high power supply quality,strong acceptance capacity and no frequency and phase problems.As one of the key issues in the future construction and planning of DC distribution network,power quality directly affects the development of DC distribution system.Therefore,this paper studies the power quality of DC distribution network.Firstly,the development significance of DC distribution network under the new power situation is analyzed,and not only analyzes the development status abroad,but also analyzes the domestic situation.Through the research and analysis of the topology structure,voltage level and some core equipment of DC distribution network,the model of two-end DC distribution network is built by using the platform of PSCAD/EMTDC simulation software,and the correctness and effectiveness of each part of device control system are verified by simulation experiments.Secondly,this paper briefly describes the types of power quality problems in DC distribution network,and by referring to the research method of power quality disturbance detection in AC system,in view of the good time-frequency local analysis ability of wavelet transform,this paper proposes a power quality disturbance detection based on improved lifting wavelet,which is compared with the previous algorithm,The detection algorithm not only improves the accuracy of disturbance detection,but also improves the detection efficiency,and is easy to implement.An example is given to verify its effectiveness by using the medium voltage DC distribution network built above.Finally,aiming at the problem of harmonics and ripple on both sides of VSC in DC distribution network,An improved control strategy is proposed,which uses dc-apf and three-level APF to suppress harmonics(ripple)respectively.By comparing with the control strategy without improvement,the control strategy proposed in this paper effectively improves the effect of harmonic suppression of active power filter,and its feasibility is verified by simulation experiments.Figure [61] Table [12] Reference [72]... |
