A Novel Approach to Dynamic Control of a Three-Phase MOSFET Power Inverter, Based on Bootstrap Constraints

Abstract

A novel model for predicting the bootstrap voltage in the dynamic operation of a three-phase MOSFET power inverter system driving an electric motor is presented. The model takes into account the bootstrap supply level, the parameters of inverter’s N-channel MOSFETs, the switches’ duty cycle at the corresponding modulation indexes, the power factor (cos(ϕ)), motor’s rpm and other details to accurately predict the boundaries of permissible AC frequencies and modulation indexes. It is based on both mathematical theorems and test results. The model was implemented and successfully tested in software running in the field on inverter/motor combinations on forklift trucks and other electric vehicles.