A Motor-Friendly Quasi-Resonant DC-Link Inverter With Lossless Variable Zero-Voltage Duration

Two quasi-resonant dc-link (QRDCL) inverter topologies are discussed for motor-friendly application. For the control of an inverter, a modified space-vector pulsewidth modulation is implemented, which requires only two resonant cycles per switching period and helps in better utilization of dc-link voltage. The first topology is tested experimentally with a 34-m-long cable connected between inverter and induction machine for reduced voltage overshoot at motor-side cable end and common-mode (CM) voltage. Even though results are satisfying, a freewheeling interval of this topology produces high losses. So a new motor-friendly QRDCL inverter with lossless variable zero-voltage duration is proposed. In this topology, during a zero-voltage interval, energy is stored in a capacitor rather than an inductor. No current is freewheeling through inverter switches, and it clearly helps in reducing the losses under a low-modulation index region. Simulation results are presented to verify the validity of the proposed inverter and its motor-friendly characteristics.