Reactive Power Compensation in Medium-Voltage High-Power Current Source Rectifier-Fed Topologies

High-power applications use Silicon Controlled Rectifier (SCR)-based converters because of their robustness and low conduction losses. These applications include DC supplies for electrolytic processes, traction, and other drives or loads that demand high power control. However, these applications face challenges with reactive power demand and harmonic distortions, especially under light load conditions or, in the case of drives, at lower speeds and torque. This article proposes a solution that uses a three-phase four-winding Wye-Wye-Delta-Wye transformer with a low-power, low-voltage source inverter (LV-VSI). Using LV-VSI-assisted commutation, one SCR rectifier operates at a leading power factor and the other operates at a lagging power factor, canceling the fundamental reactive power demands and achieving a unity power factor at the grid. This strategy is valid for any load across rectifiers. The experiment is conducted with a current-source inverter-fed hybrid motor drive load. Simulation and experimental results validate the proposed strategy to reduce reactive power while maintaining the simplicity and reliability of SCR-based rectifiers.