Modeling And Analysis Of Magnetic Field In DC Yard Of VSC-HVDC Station Under Short-Circuit Conditions

Voltage source converter based high voltage direct current transmission(VSC-HVDC)technology has significant technical advantages in large-scale new energy grid connection,island power transmission,etc.,and has been developed rapidly.Among them,the difficulty of controlling the fault current on the DC side has become one of the bottlenecks in the construction of VSC-based DC grids.Hybrid DC circuit breakers are used as one of the most ideal ways to achieve fault isolation on the DC side has been applied in engineering in recent years.With the introduction of hybrid DC circuit breakers,and the DC yard of the VSC-HVDC station adds a new magnetic field source.When a short-circuit fault occurs on the DC side,the electromagnetic influence of the strong magnetic field generated by the fault current on the secondary equipment in the DC yard is still unclear.This thesis focuses on the problem of magnetic field interference in the DC yard of VSC-HVDC station under short-circuit conditions.First,the main magnetic field disturbance sources in the DC yard of VSC-HVDC station are analyzed.The magnetic field calculation model of the hybrid DC circuit breaker,smoothing reactor,bus bar,cable and grounding grid in the DC yard is established.The quasi-magnetostatic method is used to analyze the magnetic field generated by each magnetic field source of the DC yard,and evaluates the shielding effectiveness of the metal mesh of the DC yard.At the same time,experimental measurements were carried out in the laboratory to verify the validity of the magnetic field calculation model of the hybrid DC circuit breaker and smoothing reactor.Secondly,Dinghai converter station with 200kV hybrid DC circuit breaker is taken as the research object.The fault current simulation is carried out.According to the layout of the equipment,and the magnetic field calculation model of the electrical equipment of DC yard was established.The calculation results of the current and the magnetic field are compared with the actual measurement results during the artificial short-circuit test,and the validity of the current simulation model and the magnetic field calculation model are verified.On this basis,the magnetic field at the sensitive position of the DC yard under monopolar grounding fault and pole-to-pole short-circuit fault is calculated,and the distribution law of magnetic field in DC yard is studied.Finally,Zhangbei converter station with 535kV hybrid DC circuit breaker is taken as the research object.The fault current simulation is carried out.According to the layout of the equipment,and the magnetic field calculation model of the electrical equipment of DC yard was established.The magnetic field at the sensitive position of the DC yard under monopolar grounding fault and pole-to-pole short-circuit fault is calculated,and the distribution law of magnetic field in DC yard is studied.Based on related theories,the correlation between the time-domain waveform of the magnetic field during a short-circuit fault and the magnetic field immunity test waveforms specified in the existing standards is analyzed.The model built in this paper can provide a reference for the modeling of magnetic field in DC yard of other VSC-HVDC stations,and the research results can provide technical support for the arrangement and the assessment of immunity of secondary equipment in the DC yard of VSC-HVDC stations.