Research On 3L-ANPC Converter Modulation Strategy Based On Junction Temperature Balance

Three-level neutral point clamped(NPC)converter has the disadvantage that the junction temperature distribution is unbalanced.Three-level Active NPC(ANPC)converter can solve this problem effectively.This paper takes the three-level ANPC converter as research object.The basic working principle,modulation algorithm and the loss of the converter and the problem of junction temperature balance are studied.This paper analyzes the three-level converter topology and working principle of the three-level ANPC converter three basic pulse width modulation(PWM)methods.Aiming at the neutral point potential characteristic of NPC three-level converter,a method to solve the problem are researched in this paper.Besides The dead time effect of three-level ANPC converter is analyzed and the dead time compensation algorithm is designed.In order to study the distribution characteristics of three-level ANPC converter power device loss and junction temperature,the switching process,loss model and thermal network of the insulated gate bipolar transistor(IGBT)and power diode are studied,and the calculation model of IGBT module is designed.On this basis,the distribution characteristics of power device loss and junction temperature of three-level ANPC converter under the three basic PWM methods are studied.The relationship between the conversion mode and the maximum junction temperature of power devices is analyzedThis paper studies the modulation strategy of three-level ANPC converter,with the sine pulse width modulation(SPWM),the space vector pulse width modulation(SVPWM)and the selected harmonic elimination pulse width modulation(SHEPWM)respectively introducted.In order to make full use of the advantage of three-level ANPC converter,this paper presents a temperature feedforward SHEPWM strategy,and simulation and experimental verification are carried out.The results show that the proposed method can effectively balance the power dissipation and the junction temperature distribution of the device,and eliminate the low order harmonics.Finally,on the three-level ANPC converter experimental platform,the paper has completed the experiments of the three modulation algorithms,the neutral point potential balance control,the dead time compensation and the temperature equalization modulation strategy.The experimental results verify the feasibility and effectiveness of the three-level ANPC converter modulation strategy.