Transformer-less series voltage injection for reactive power compensation of line-commutated HVDC

A transformer-less series-voltage injection strategy has been suggested for reactive power compensation of line-commutated HVDC systems. It has been shown that series voltages injected at appropriate times using transformer-less full-bridge arrangement can force early commutation on the rectifier side thereby bringing the phase angle between the voltage and current to a smaller value than the conventional 15° value. Simulation results indicate reactive power compensation as well as reduction in consumption by the HVDC terminal. This can lead to smaller HVDC terminal size due to elimination of shunt-capacitor-bank requirement. The results indicate that the requirement for capacitors in the suggested topology is much smaller than fixed series capacitor.