Control of active injector for multi-pulse rectifiers operating on variable frequency supplies

A control strategy is described to drive an active injector for multi-pulse rectifiers operating on variable frequency aerospace supplies. The injection technique utilises a single low-rated active device that carries approximately 2.9% of the load current, and this may be driven with either low-frequency pulses or high-frequency, pulse-width modulation to produce 24-pulse operation or multi-level PWM operation respectively. The resultant input currents are almost sinusoidal, the line current THD being 2.36% for the 24-pulse operation and 1.06% for the PWM operation. The control principle, design and performance are presented in this paper. Experimental results of the controller with a 4 kW prototype are shown.