Synchronous modulation strategy for multi-objective optimization of traction converters under five-division frequency operation conditions
Restricted by heat dissipation conditions,the switching frequency of the traction inverters for rail transit typically re-mains below 1 kHz,to prevent potential shortening of their service lifetime due to excessive switching losses in power devices.Inverter operation in the middle and high-frequency ranges results in a decrease in carrier ratio,leading to amplified output harmonics.This not only lowers output performance but also elevates peak current levels,intensifying power losses within the insulated-gate bipolar transis-tor(IGBT)and consequently undermining driving safety.Unlike existing modulation strategies to address low carrier ratios,which most-ly focus on optimizing output performance while overlooking the suppression of IGBT power losses,this paper presents a multi-objec-tive optimization modulation strategy for traction inverters under five-division frequency.This strategy aims to maintain a low weighted total harmonic distortion(WTHD)in the inverter output while reducing total power losses.Firstly,numerical and phase relationships be-tween the output voltage and current were established based on the inverter load model.A precise discrete calculation model for IGBT power losses was developed based on the data manual provided by the device manufacturer,leveraging the power loss generation mecha-nism.Subsequently,the switching angles were solved under the premise of ensuring the fundamental amplitude of inverter output voltag-es aligned with the reference level,to enable multi-objective optimization modulation for inverters,including both inverter output current harmonics and power losses as optimization objectives.Simulation results indicate that within the operating range,the proposed optimi-zation modulation strategy significantly reduced IGBT power losses and remained superior output performance compared to traditional strategies.
converterpower lossfive-division frequencymulti-objective optimization modulationweighted total harmonic distortionswitching angle
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