Analysis and design of a three-level PWM converter system for railway-traction applications

The paper analyses the merits and demerits of three-level PWM converters through the comparison with two-level PWM converters. A general method for analysing the switching modes of PWM converters is described and an analysis of the three-level PWM converter is presented as an example. A neutral-point voltage-balance-control algorithm together with its hardware and software implementation is presented. A three-step methodology of rapid prototyping by using CAD for the system design, using a real-time simulator for checking the implementation and using high-power testing for validating the system, is described.