Three-Level Rectifier Fed Four-Level Inverter for Electric Drives

A special four-level three-phase diode clamped inverter fed by a correspondingly adapted untypical three-phase rectifier with two typical transformers is presented. The three-level rectifier is formed by consecutive connection of three rectifiers under the circuit of Scott for the bi-phase orthogonal voltage received from corresponding windings of two three-phase transformers. The inverter is realized by 4,5kV IGBT modules and provides a voltage of 6 kV (RMS) for a high power induction machine without transformer. The dependences of THD and integral values of THD of output voltage are simulated and shown for simple variants of three-carriers PWM and SVM.