Control strategies of the quasi-resonant DC-link inverter

Control strategies of a parallel quasi resonant dc link voltage inverter (PQRDCLI) for electrical drive applications are considered. The main objectives of the proposed strategies are feasibility and robust operation of the PQRDCLI vis-a-vis output voltage dU/dt limitation and stable duration of zero voltage intervals. The first strategy is based on controlling equal charge and discharge of the input series capacitor bank. By applying in the second strategy, external dc link voltage power supply converters one can precisely stabilize both the output voltage derivatives and zero voltage interval. Finally, in the third sensorless strategy - constant intervals are applied with the floating capacitor midpoint potential variations.