Modified PWM control method for neutral point clamped multilevel inverters

Abstract

In this paper, a new modified PWM (pulse width modulation) control method for any type of neutral point clamped (NPC) multilevel inverters is proposed. In NPC inverter topologies with more than three-level, the problem of charge balance in the split dc-link capacitors is still discussable. Hence, the most important advantage of the proposed pulse width modulation (PWM) control method is keeping the charge balance of capacitors in the neutral point (NP). To check the correct operation of the proposed PWM control method, the structure of conventional three-phase NPC five-level voltage-source inverter is also used. In this paper, different combinations of permissible switching states for five-level NPC inverter based on voltage-source is presented. Moreover, the control signals are explained for NPC five-level voltage-source inverter by using both conventional and proposed PWM control methods. In this paper, a comparison between conventional and proposed control methods is performed. The simulations performed in PSCAD software are done for both conventional and proposed PWM control methods. The good performance of the proposed control method compared to conventional control method is verified by the simulation results.