Current harmonic minimum pulse width modulation for three-level inverter
Limited by the heat dissipation conditions,the switching frequency of inverters in high-power traction drive systems is usually very low.Three-level inverter topology is widely used in medium/high-voltage and high-power fields because of its small output harmonics and low dv/dt.Taking the three-level neutral-point-clamped inverter as the research object,a current harmonic minimum pulse width modula-tion ( CHMPWM) was proposed.Based on the optimization objective of minimizing weighted total har-monic distortion,the switching angle curve under different number of switching angle were solved.The harmonic performance was compared with the selected harmonic elimination pulse width modulation,which is widely used at present.Although the modulation method proposed cannot eliminate specific har-monic,the overall current harmonic reaches the minimum.Aiming at the difficulties and problems in the implementation of CHMPWM,a multi-mode modulation strategy based on CHMPWM in full speed range was designed.Simulation and experimental results show that the proposed CHMPWM has good harmonic performance,which is consistent with the theoretical analysis results.