Research On Inverse System Sliding Mode Control Method Of Cascaded STATCOM

With the increasing of the Gas Insulated Substation(GIS)in the power grid,to eliminate the failure in the bud and avoid serious accident,effective and reliable detection for Partial Discharge(PD)fault in GIS has become an urgent demand.Therefore,based on the existing diagnostic methods,multi-dimension diagnostic method is proposed to deal with the PD problem in different stage on different condition.The multi-dimension diagnostic method is to adopt different means to diagnose the PD fault in the different situation of GIS,including before operation and online operation and maintenance.Firstly,based on the recent statistics about the failure rate of the GIS PD defects,four models of typical GIS PD defects which have been defined by researchers are used in the experiment in the experiments in this thesis.The four models are proved to be practical and reasonable by pulse current method recommended by IEC-207.Secondly,by the test under the Negative Standard Lightning Impulse Voltage,the characteristics and relevant law of PD are obtained.Thirdly,aiming at the problem of white interference in PD signals by the Ultra High Frequency(UHF)Online Monitoring Fault Diagnosis in GIS,the Empirical Mode Decomposition(EMD)method is presented to denoise.The effect of denoising is not only reflected in the simulation,but also proved to be effective in practice.However,it has laid the foundation for the PD fault location.Finally,in order to confirm the status of PD components in GIS and shorten the maintenance period for GIS,a X-ray digital imaging system is applied to determine the scope of the PD fault,As a result,the GIS fault point could be accurately identified and judged in the case of no disassembly.According to the above research for GIS PD diagnosis methods,the PD characteristics of the UHF signals could be eliminated effectively.The multi-dimension diagnostic method in the dissertation provide a theoretical basis for the reasonable evaluation for GIS insulation and safe operation.