Key Technologies Research Of KA-Level High Repetitive Pulse-Current Source

Pulsed-current source is widely used in industry and national defense.Especially,the demand for kA-level high repetitive pulsed-current source is gradually increasing in nuclear physics,high energy laser,electromagnetic compatibility,lightning test and electric power systems,etc.Therefore,the working stability and output repeatability are the hot spots in pulse current source in recent years.At present,the stability of kA-level pulsed-current source is mainly guaranteed by the redundant design of discharge topology and the derating use of key devices.As for the output repeatability,it is mainly improved by the low-jitter switch and highprecision trigger control system.These schemes not only increase the cost and volume of the pulsed-current source,but also lead to frequent design iterations and complex operation controls.To overcome the above shortcomings,considering the current trends in pulsedcurrent source(high power and high repetition frequency),a series of related researches on kA-level pulsed-current source are carried out in this paper.Specifically,for the initial power supply,the research of current sharing detection technology based on parallel power supply is carried out.For the energy storage systems,the research of capacitance measurement under high DC bias is carried out.Through these studies,it is expected to provide accurate parameter settings for operation state monitoring,optimal control,and optimal system design of pulsed-current source,and improve the working stability and output repeatability.The main research contents of this dissertation are concluded as four aspects:a)The basic theory and typical circuit topology of kA-level pulse-current source are studied.Combining with the trends and application background of pulsed-current source,the influences of initial power supply,energy storage systems and pulse shaping and conversion on the working stability and output repeatability are analyzed.Based on these analyses,the significance of monitoring and feedback of initial power supply and capacitance measurement for energy storage capacitor under high voltage is expounded.b)By modeling the switching signal of the power supply and analyzing the spectral characteristics of the output ripple,the relationship between the switching frequency and the output power is established.Based on this,a CNN+LSTM based weak spectrum feature recognition method is proposed.The experimental results show that,the proposed method can realize the system current-sharing state judgement and branch identification only through a single point detection at the load,which effectively avoid the disadvantages of the traditional method of deploying sensors and cables in all power supply branches,greatly reduces the detection cost and operation complexity,and provides an effective way for the working stability detection and control of kA-level pulsed-current source with parallel power supply.c)A high voltage capacitance measurement method based on alternating coupled signal injection is proposed.The proposed method utilizes the impedance conversion of the transformer and the output retention characteristic of the constant current source,establishes the mapping between the capacitance variation and the voltage at both ends of the constant current source,and realizes the safe isolation test of the capacitance under 3k V DC high voltage bias which breaking through the limitation that the DC bias voltage is generally below 1k V in the traditional method.The measurement results have high accuracy and traceability,and the characteristic curve that the capacitance of pulse power multilayer ceramic capacitor decreases with the increase of DC bias is accurately measured with 1% accuracy,which provides the technical and data support for the accurate design of energy storage system in kA-level pulsed-current source.d)Based on the nonlinear characteristics of pulse power multilayer ceramic capacitor,a high-precision discharge circuit is designed and the underdamped pulse current waveform output with peak current amplitude of 4kA?6kA and oscillation period of 2.8?s,3.6?s,3.8?s and 4.4?s is realized.The repeatability of peak amplitude of pulse current and oscillation period are better than 1%.The evaluation system of kAlevel high repetitive pulse-current source is established.Through the evaluation system,the influence of capacitance variation of energy storage capacitor on kA-level pulsedcurrent source output is analyzed,and the significance of high voltage capacitance measurement in kA-level pulsed-current source design is verified.In addition,the pulse current amplification method under the limited device performance is also explored.Specifically,based on the equivalent ampere-turns method,a transient current multiplier is developed,which achieves amplitude amplification and high fidelity of waveform characteristics.The over-damped induced current with peak amplitude of 20 kA is obtained,and the repeatability of peak current amplitude and pulse width is better than0.2%,which provides a new way for generating kA-level high repetitive pulse-current signals.Through the research on common problems such as current sharing state detection of parallel power supply,high-voltage capacity measurement and transient current multiplication technology,it provides theoretical and data support for the working state monitoring and evaluation of kA-level pulse-current source,accurate design and cost control of energy storage system,and re-amplification of kA-level pulse-current under the condition of limited device performance.