High power machine drive, based on three-stage connection of "H" converters, and active front end rectifiers

A three-stage inverter using "H" converters is being analyzed for high power machine drive applications. The great advantage of this kind of converter is the minimum harmonic distortion obtained at the machine side. The drawbacks are the isolated power supplies required for each one of the three stages of the multiconverter. In this paper this problem has been overcome in two ways: 1) by using independent windings for each phase of the motor, or 2) by using independent input transformers. Special configurations and combinations of passive rectifiers and active front end rectifiers for one of the stages of the drive are used to eliminate all input harmonics. The topology can also keep unity power factor at the input terminals. Simulation results are shown and some experiments with small four-stage prototypes are displayed. The control of this multi-converter is being implemented using DSP controllers, which give flexibility to the system.