Neutral-to-ground voltage minimization in a PWM-rectifier/inverter configuration

High frequency common mode voltage produced by power converters are a major cause of conducted EMI, creating motor ground currents, bearing currents and other harmful by-products. In this paper a control algorithm for an induction motor fed by a fully controlled rectifier and inverter is developed to reduce the common mode neutral-to-ground voltage of the induction motor. A bearing current model is used to evaluate the effects on the bearing currents of the double bridge modulation scheme when the new algorithm and conventional algorithms are used. Simulation results are shown to demonstrate the benefits of the new PWM approach.