Research And Implementation Of Minimum Fluctuation Reference Discontinuous Pulse Width Modulation For Three-phase Inverter

The function of three-phase inverter is to convert DC voltage to three-phase AC voltage.As a kind of power conversion device widely used in industrial field,it plays a very important role.The practical application platforms of three-phase inverter include photovoltaic power generation,wind power generation,motor speed regulation,DC voltage stabilizing power supply,uninterrupted power supply,ship integrated power system and electromagnetic rail gun,etc.Therefore,the research on improving the performance of three-phase inverter has high theoretical and industrial value.The main performance indexes of three-phase inverter are DC voltage utilization,common-mode voltage(CMV),total harmonic distortion(THD)and switching loss.The main methods to improve these performance indexes are to optimize the designs of pulse width modulation(PWM),such as space vector modulation,third harmonic sine PWM,maximum minimum mean modulation and discontinuous PWM,etc.Although the linear modulation index of the inverter can reach the theoretical maximum,these modulation techniques will bring adverse effects on CMV,switching loss and voltage distortion.In this paper,a Minimum Fluctuation Reference Discontinuous Pulse Width Modulation(MFRDPWM4)technique is proposed,the reference of modulation technique injects the least zero sequence signal of Discontinuous Pulse Width Modulation type 4(DPWM4).Through theoretical analysis,the technology can make the inverter have high DC voltage utilization ratio,and improve the performance index of CMV,voltage distortion and switching loss of the inverter.In order to verify the feasibility and effectiveness of this scheme,the simulation and experimental platform of three-phase inverter and modulation scheme is built in this paper.In the aspect of simulation,the Simulink module of Matlab software is used to simulate the inverter circuit and modulation scheme.As for the realization of the actual platform,the hardware circuit and control software code of the inverter are designed.The main circuit of the inverter adopts the intelligent power moduleFNB51560T1.The input PWM drive signal of inverter is generated by digital signal processor TMS320F2812.The performance of the inverter under the minimum fluctuation discontinuous PWM scheme is studied through the simulation and the experiment of the actual platform,and the experimental results of the conventional modulation scheme are compared and analyzed.The experimental results verify the effect of the modulation scheme on the comprehensive performance of the inverter: the scheme not only can improve the DC voltage utilization of the three-phase inverter,but also can reduce the third harmonic of the CMV,and the THD and the switching loss are also low.