A HIGH-POWER PWM QUADRATURE BOOSTER PHASE-SHIFTER BASED ON A MULTIMODULE AC CONTROLLER

Pulse-width-modulated (PWM) phase shifters allow the smooth control of power flow in a transmission line. This paper analyzes a PWM quadratu re booster phase shifter based on a multimodule ac controller structur e to attain high voltage levels and improve the harmonic spectrum. The modules are based on a three-phase PWM ac controller topology that em ploys only four force-commutated switches and is controlled by duty-cy cle variation. The PWM technique is carrier based, and the individual modules are gated through phase-shifted triangular carriers. As a resu lt, harmonic cancellation takes place in the input current and output voltage. Low-order harmonics are therefore eliminated and the amplitud e of remaining components reduced. An additional operating mode with n egligible harmonic generation and step-like control is identified. The feasibility and advantages of the proposed phase shifter are demonstr ated by means of a power system simulator.