| With advantages of small size, specific, high efficiency and long lifetime the HallThruster is mainly used in the task of spacecraft attitude controlling, station keepingand orbital adjustment and so on. Therefore hall thrusters are increasingly favored byall space powers. However, low frequency oscillation of the discharge current withintens of kHz frequency is always observed in actual operation which has largeamplitude oscillation. Because tens volts changes of discharge voltage can be initiatedby several amperes changes in the discharge current, voltage changes will causenegative effects of the DC power and may affect the lifetime and performance of thethruster, seriously even can lead to extinction thruster. Therefore, the low frequencyoscillation phenomenon has been one of the hot issues which is focused by researchinstitutions in the world.As low frequency oscillation is a universal phenomenon when Hall thrusters areworking, simulative researchs are carried out in this article mainly in its effects in thewall corrosion and thruster performance, the outer loop of discharge designing and soon. Based on the microscopic physical mechanism of low frequency oscillations itssuppression method is proposed and the parameters of the filter structure isoptimization researched from the perspective of macro. Firstly, the One-DimensionalHydrodynamic Model is improved in aspects of adding performance parametersmodule, adding the self-excitation module and holly considering the role of thecapacitor. Secondly, compared with different excitation modes of Hall thruster thearticle analyses the intensity of oscillations. Through comparing and analysing of themovement of electrons and ionization fronts inside the discharging channel thephysical mechanism of low frequency oscillation is described. After that, the methodsof suppressing low frequency oscillations are put forward which can add to analternating component of the excitation current with certain amplitude and the samefrequency as low frequency oscillation in the basis of the original DC excitationcurrent to suppress the development of low-frequency oscillation that has achievedgood results with a simulate method. Thirdly, as large amplitude oscillations of currentand voltage can cause negative effects in the power when the Hall thruster is working,parameters of the filter are set optimizedly by the control variable method which make the power operate safely and provide guidance for the actual. At last, the effect of lowfrequency oscillation and performance are discussed which is caused by the channelwall erosion at the late life of the Hall thruster. Then different characteristics oflow-frequency are given in different life of the thruster which can reasonablely set thedesign margin of outer loop parameter to suppress low-frequency oscillations inlifetime of the thruster. It provide relevant reference to ensure the thruster workingstable in the lifetime. |
