Research On Generation Mechanism And Measurement Methods Of Supraharmonics

With the development of society and the advancement of technology,household appliances such as electric vehicle charging piles,household energy-saving lamps,and electronic device chargers have gradually become popular.On the other hand,new energy generation equipment such as photovoltaic power generator and wind power generator has been connected to the power grid on a large scale.All the above have caused the use of power electronic switching devices is increasing,which resulted in the high-frequency development trend of the harmonics flown into the power grid.The frequency range of supraharmonics which is from 2k Hz to 150 k Hz is much wider than normal harmonics,and the propagation characteristics of supraharmonics are more complicated.The two points above make the research of supraharmonics much more difficult.The supraharmonics are likely to affect the power equipment in the vicinity,and studying it will help to ensure the stable operation of the future power grid.The study of the generation mechanism and measurement methods of supraharmonics are conducted in this thesis.In terms of the generation mechanism of supraharmonics,the supraharmonics test data of various equipment are analyzed and the supraharmonics sources are divided into three categories: energy-saving lamps,switch-type power electronic equipment,and other equipment.The supraharmonics generation mechanisms of the three categories are analyzed according to the test data.Then,MATLAB/Simulink is used to build the APF simulation model for analysis.After analyzing the simulation results,it is found that the supraharmonics frequency peaks appear at the APF switching frequency and its multiple frequencies.In terms of measurement methods for supraharmonics,the basic measurement method-Fourier transform is introduced briefly.The measurement methods proposed in the IEC standards are introduced in three directions: partial sampling,spectral aggregation,and spectral segmentation.Then the advantages and disadvantages of these harmonic measurement methods are analyzed through MATLAB/Simulink simulation and the adaptability of these measurement methods when using in the supraharmonics frequency band is discussed.Combining the measurement methods in the existing standards with the actual engineering,a hybrid segmentation measurement method based on the switching frequency of the device under test is proposed in this thesis.Then the simulation is performed through MATLAB/Simulink according to the data generated from the ideal supraharmonics source to analyze the measurement method.Besides,the measurement method is tested based on the data obtained from the field test in the State Grid Corporation "Power Harmonic Characteristics Analysis and Evaluation Technology Laboratory".Both the simulated and field-test results show that the measurement method proposed in this thesis is effective and practicable.