A PWM QUADRATURE-BOOSTER PHASE-SHIFTER FOR AC POWER TRANSMISSION

The conventional structures used for phase shifters employ quadrature voltage injection controlled by means of on-load tap changers that req uire considerable maintenance, Line-commutated thyristor structures ha ve been proposed to replace tap changers, but problems related to filt er requirements or the number of switches have limited their utilizati on, This paper proposes a pulse width modulation (PWM) quadrature-boos ter phase shifter based on a force-commutated ac controller. It offers features such as fast dynamic response, continuous variation of the p hase angle with low harmonic injection, and it requires a simple power structure and can be controlled by adjusting the duty cycle of the sw itches, The operating principles of the proposed phase shifter are ana lyzed and their feasibility is demonstrated through digital simulation and experimental implementation.