Electric drive with voltage-fed inverter with regard to influence of voltage sag

This paper solves problematic of immunity of electric drive from the voltage sags on the power supply. Typical modern electric drive consist of the induction machine (or synchronous machine) supplied from indirect frequency converter with voltage-fed inverter and with non-controlled rectifier (or other - more complicated type of input side of this frequency converter). For this configuration are compared some variants how to achieve high immunity from the voltage sags. There are reflected opportune control algorithms (for induction machine etc.) for the quickly to change of working regime from full load in regime “drive” to “no-load” regime (to achieve for approximately constant value of voltage in capacitance in DC-link) and opportune control algorithms for quickly to return to original working regime after the regeneration of energy supply. There are also referenced the variants of adaptation of power circuits for to achieve a higher of immunity from the voltage sags. Special attention is paid to the using the special additional step-up boost converter in DC-link (with some variants of power circuits and with some variants of control algorithms for this type of additional converter). These theoretical assumptions were verified by simulation in PC (program Matlab/Simulink + Plecs) and by measuring on real laboratory system.