A PWM quadrature booster phase shifter for AC power transmission

The conventional structures used for power system phase-shifters employ quadrature voltage injection controlled by means of on-load tap-changers that require considerable maintenance. Line-commutated thyristor structures have been proposed to replace tap-changers, but problems related to filter requirements or the number of switches have limited their utilization This paper proposes a PWM quadrature booster phase shifter based on a force-commutated AC controller. It offers features such as fast dynamic response and low harmonic injection, requires a simple power structure and can be controlled by adjusting the duty cycle of the switches. The operating principles of the proposed phase shifter are analyzed and its feasibility is demonstrated through digital simulation and experimental implementation