A new mathematical tool to investigate the influence of cable characteristics and IGBT fast switching on voltage transients and differential mode currents for PWM drives

Abstract

The authors propose a new mathematical tool to investigate the influence of cable characteristics upon pulse voltage transients and their associated differential mode (DM) currents in PWM long cable drives. Even if reflected wave transient voltages have received considerable investigation for IGBT voltage source inverters, the modeling and simulation of these voltage transients still require precise modeling. Moreover, another consequence of the IGBT fast rise time, which is the resulting high frequency DM current, has not been previously examined in detail for these systems. This paper presents fully developed mathematical formulas for both pulse voltages and their resulting DM currents at any point along the inverter-to-motor cable. Using the developed formulas, an appropriate tool has been built, using SimPowerSystems (SPS) and Simulink of Matlab software, to predict the high frequency over-voltages and their associated DM currents all along the feeding cable. This tool has then been applied to an industrial 5 kV A PWM drive prototype using a 4-wire shielded long cable. Some simulation results and experimental validations are included.