PWM Three-Level Inverter Control

This paper analyses a PWM control circuit for a three-level three-phase inverter. The power circuit of inverter and the PWM control principles, using a mirror triangular waveform, are explained. The output voltages of the inverter are represented by 21 Park vectors, from which 3 vectors are null. The PWM circuits with synchronization, used to control the switches of the inverters, are inserted. A circuit that changes instantaneously two phases each other, maybe used for reversible electric drivers, is proposed. The principle of this circuit issues from producing of two triangular waveforms in quadrature, that by a functional transform are converted into sinus and cosines; these waveforms are inputs of PWM modulator. Experimental results, introduced here, confirm all theoretical assumptions