面向脉冲负载供电系统的传导电磁干扰机理与电磁安全评估OA

Pulsed power load supply systems operating under dynamic conditions generate more complicated conducted electromagnetic interference(EMI)than conventional steady-state converters because of the interaction between low-frequency pulse dynamics and high-frequency switching harmonics.Existing conducted EMI studies mainly focus on steady-state operating conditions,whereas the EMI formation mechanism and electromagnetic safety characteristics under pulse operating conditions remain insufficiently understood.This paper investigates the conducted EMI mechanism and electromagnetic safety assessment of pulse load power supply systems. A phase-shifted full-bridge converter was selected as the research object.First,a differential-mode conducted EMI analytical model was established by regarding the converter input current as the differential-mode noise source and incorporating the line impedance stabilization network(LISN)into the equivalent circuit.Subsequently,a multi-time-scale analytical framework was developed to describe the interaction between low-frequency pulse dynamics and high-frequency switching harmonics.The pulse load current was decomposed into DC and AC components,and an input current spectrum model was derived by linearizing the harmonic components around the operating point.The analytical results revealed that the low-frequency pulse current dynamically modulates the converter switching harmonics,producing modulation sidebands distributed at kfs±nfp,where fs and fp denote the switching frequency and pulse frequency,respectively.Based on the proposed model,the influences of pulse peak power,pulse frequency,and pulse duty cycle on the conducted EMI spectrum were analyzed.Finally,an experimental platform was established to validate the theoretical model under different pulse operating conditions. Experimental results showed that the proposed model accurately explained the evolution of the conducted EMI spectrum under pulse operating conditions.As the pulse peak power increased,the harmonic amplitude of the converter input current increased correspondingly,resulting in a higher differential-mode conducted EMI level.Compared with steady-state operation,pulse operating conditions introduced additional low-frequency modulation components,leading to a more complicated conducted EMI spectrum.Increasing the pulse frequency generated denser modulation sidebands and caused the low-frequency EMI spectrum to evolve from discrete spectral components to a continuous spectral envelope.Variations in pulse duty cycle mainly redistributed the spectral envelope by changing the harmonic energy distribution of the pulse current.The predicted modulation sidebands agreed well with the experimental results.Moreover,the coupling among the input filter,parasitic parameters,and pulse current harmonics enhanced the input current oscillation under high-frequency pulse operating conditions.Compared with steady-state operation,the conducted EMI amplitude around 10 kHz and 50 kHz increased by approximately 25.82 dBμV and 23.23 dBμV,respectively. The results indicate that pulse load dynamics increase not only the complexity of the conducted EMI spectrum but also the electromagnetic safety risks of the power supply system.The coupling between low-frequency pulse harmonics and high-frequency switching harmonics aggravates local resonance,impedance mismatch,and dynamic instability,particularly under high-power and high-frequency pulse operating conditions.Therefore,pulse dynamic characteristics,converter switching harmonics,system impedance matching,and filter design should be jointly considered in conducted EMI analysis and electromagnetic safety assessment. The following conclusions can be drawn from the simulation analysis:(1)A multi-time-scale analytical model is established to describe the coupling mechanism between pulse load dynamics and converter switching harmonics.The analytical model reveals that the pulse current dynamically modulates the high-frequency switching harmonics,producing modulation sidebands distributed around the switching frequency and its multiples according to kfs±nfp.(2)Pulse peak power,pulse frequency,and pulse duty cycle affect different characteristics of the conducted EMI spectrum.Pulse peak power mainly determines the amplitude of differential-mode conducted interference,pulse frequency governs the sideband spacing and spectral spreading,whereas pulse duty cycle controls the spectral envelope and harmonic energy distribution.(3)Pulse load dynamics increase the input current oscillation and further aggravate the conducted electromagnetic environment by enhancing the risks of local resonance and dynamic instability.Consequently,electromagnetic safety assessment and EMI suppression for pulse load power supply systems should simultaneously consider pulse dynamic characteristics,converter switching behavior,and system impedance matching.