Harmonic Characteristic Analysis Of Ningxia AC-DC Power Grid

In a variety of power generation forms and AC&DC combined transmission main structure,the power quality of the power grid harmonic pollution is deteriorating.For the the harmonic problem of AC&DC interconnection,many experts and scholars at home and abroad analysed and researched the problem from different aspects and made a breakthrough.At present,the problem to be solved is how to establish an accurate and reliable simulation model based on the measured data so that the measured value can be calculated in some way,and then the harmonic characteristics of the whole grid can be grasped,and the harmonic data needed for the design of the grid filter is put forward.The research methods of this paper can be summarized as follows:1)Through harmonic testing of the whole process of the DC line stable operation and maintenance period,the harmonic characteristics and its main influencing factors are analyzed,and the transmission law of harmonics is summarized.The harmonic source model and harmonic source data of the power grid are given by the analysis of the measured data.2)Power grid is set up based on ETAP software,and the harmonic source is injected into the equivalent model,using the method of data simulation analysis,and comparative analysis of simulation values and measured values verify the accuracy of the model reliability.3)The harmonic value of 750 kV double-loop network in Ningxia power grid is calculated under different operating modes of DC power,at the same time the harmonic condition of 330 kV AC side and main transformer 750 kV are compared in order to realize the comprehensive grasp of the harmonic distribution of the power grid.Under this background,the harmonic level of the Shanghai temple DC bus side is obtained which provides background harmonic basis for the Shanghai Temple DC transmission engineering AC filter design.The results of this paper can be summarized as follows:1)Measured data analysis,5th harmonic of Ningxia power grid is the dominant harmonic,but Yinchuandong main transformer 750 kV and 330 kV side 3,7,11,13 harmonic and commutator 330 kV side 11,13,23,25 harmonic are large;when DC is at stable operation,the amplitude of characteristic harmonic increase and decrease the same law;when DC is at maintenance,5,7 harmonic is small,which proves that 12 pulsating converter transformer has a role in offset on the 6k±1 harmonic.2)Using ETAP simulation software as the platform to form the equivalent model of Ningxia power grid 750 kV double-loop network,through the debugging and testing of the simulation model,it is more suitable for the calculation of harmonic power flow in different cases.After the measured values are consistent,a reliable simulation model of harmonic simulation is obtained.3)Based on the equivalent model,the DC operation mode is changed and the harmonic distortion rate of the power grid is large when there is no DC current,and the harmonic amplitude is also large.In a DC operation,the harmonic distortion rate decreases.Sub-harmonic amplitude is also smaller;Two DC power grid harmonic is smaller than a DC.This is caused by the DC power supply and the system capacity of short-circuit increasing.4)The background harmonic level of the Shanghai temple DC transmission project is calculated,and on this basis,the 500 kV bus side recommended value is given for the design of the AC filter.