Input characteristics of variable modulation current source inverters

The input characteristics of a modified CSI (current source inverter) with improved performance characteristics have been investigated. The quality of the input AC line currents is analyzed, and a design procedure for the input filters is given. Equations describing the steady-state operating characteristics are derived. These have been used to compare the input characteristics of the modified CSI with those of other CSI control schemes also using a phase-controlled front and rectifier. These comparisons have shown that the advanced features of the modified CSI are obtained without any penalty on input power factor and system efficiency. In particular, the combined displacement and distortion power factor for unity modulation index is only slightly lower than that of a six-step inverter and other CSIs also using pulse width modulation. The input characteristics of the modified CSI have been verified on an experimental 5 kVA unit and confirm the predicted results