Research On Development And Neutral Point Potential Control Method Of 3-level Inverter Based On DPWM3

With the continuous development of new energy technology,NPC type three-level inverters are more and more widely used in medium-voltage and high-power applications.Discontinuous Pulse Width Modulation(DPWM)can reduce some switch loss and improve the conversion efficiency of NPC type three-level inverters.DPWM3 is a modulation strategy of DPWM.Maintaining the balance of neutral point potential on the basis of DPWM3 modulation strategy has important theoretical and practical significance.The main work of this paper is as follows:(1)This paper studies the DPWM3 modulation strategy,and gives the realization steps of the DPWM3 modulation strategy,including the judgment of the sector where the reference vector is located,the calculation of the space vector action time,the distribution of the switch state,etc.the DPWM3 modulation strategy is simulated in MATLAB.(2)This paper studies and analyzes the causes of the neutral point potential imbalance of three-level inverter and the influence of different space vectors on the neutral point potential.Aiming at the problem of the neutral point potential imbalance of NPC three-level inverter under DPWM3 modulation strategy,redundant small vectors and small vector action time adjustment factors are added to control the neutral point potential balance by adjusting the small vector action time,the control method of neutral point potential balance is simulated in MATLAB.(3)According to the performance requirements,an experimental platform of NPC type three-level inverters is set up,the hardware circuit of NPC type three-level inverters is designed in detail,the software design of NPC type three-level inverters is given in detail flowchart,the DPWM3 modulation strategy and the control method of point potential balance are experimentally verified on the experimental platform of NPC type three-level inverters.The simulation and experimental results verify the feasibility of the DPWM3 modulation strategy and the rationality of the circuit design.The simulation and experimental data show that the midpoint potential balance control method used in this paper can control the midpoint potential balance in 5s~10s.