Wideband Modeling And Its Application Of High Frequency Energy Supply System Of Hybrid DC Breaker

The energy supply system of hybrid DC breaker plays an important role in ensuring the normal operation of DC breaker and the fast fault-clearing of DC grid.High-frequency magnetic coupling energy supply technology is of great significance to promote the development of the miniaturization of hybrid DC breaker,but lacks engineering operation experience and systematic theoretical research.This dissertation is devoted to the electromagnetic characteristics analysis and reliability mechanism research of the high-frequency energy supply system of DC breaker.The high-frequency energy supply system prototype of a 200kV hybrid DC breaker is taken as the research object,by the means of combining experimental measurement with theoretical analysis.The broadband equivalent circuit models of the core components of the high-frequency energy supply system are established,and are furtherly applied to the analysis of voltage and current transmission characteristics and the prediction of electromagnetic interference level of the high-frequency energy supply system.The work of this dissertation provides guidelines for parameter optimization and electromagnetic compatibility design for energy supply systems of DC breaker.Firstly,the broadband equivalent circuit models of the core components of the high-frequency energy supply system--the cascaded power supply transformer,the energy-taking magnetic ring and the insulated cable loop is established.By analyzing the resonance characteristics of the impedance characteristics of cascaded power supply transformers,the relationship between the resonant frequency of the impedance of the cascaded power supply transformer and the parasitic capacitance parameters is revealed.A method of extracting the parasitic capacitance of the cascaded power supply transformer in integrated package is proposed..Through the comparison of experimental measurements and simulation data,it is verified that the broadband equivalent circuit model and parameters are effective in the frequency below 1MHz.Secondly,the broadband model of high-frequency energy supply system is applied to the analysis of voltage and current transmission characteristics.The effects of parasitic capacitance and load properties on the voltage and current transmission characteristics of high-frequency energy supply systems are studied.The of high-frequency energy supply system is analyzed.The sensitivity of the current transmission characteristics to changes in various parameters of the system are also analyzed.Then,the broadband model of the high-frequency energy supply system is applied to the analysis of differential mode interference in the DC circuit breaker energy supply system under transient magnetic field.It is revealed that the inductive coupling path of the hybrid DC circuit breaker and its energy supply system is mainly the mutual inductance coupling of the main branch,the transfer branch and the energy-consuming branch respectively to the energy-supply insulated cable loop.Moreover,the waveform function of differential-mode interference voltage source generated by the transient magnetic field in the case of the hybrid DC breaker cleaning fault current and lightning current intrusion condition is extracted.Then the dissertation gives the simulation result of the differential mode overvoltage and overcurrent levels of the key ports inside the energy supply system,and proposes suppression measures.Finally,the broadband model of the high-frequency energy supply system is applied to the common mode interference under transient electric field and its conversion into differential mode interference.The capacitive coupling path between high-voltage DC circuit breaker and high-frequency energy supply system is revealed.The three unbalanced factors that convert common-mode interference into differential mode interference are summarized.Based on the broadband equivalent circuit model of high-frequency energy supply system,simulation obtained the common mode interference under the overvoltage and ground potential uplift conditions,as well as the differential mode interference level caused by it,and suppression measures are proposed.