Bi-directional real and reactive power control using a novel PWM method

A, simple control technique for the bi-directional real and reactive power flow between DC source and AC grid is presented. A 3-phase, three-wire AC grid system is considered. It is shown that for each 60deg duration of the line cycle, the 3-phase bridge can be considered as dual buck, buck & boost, or dual boost topology depending on the power factor angle of the injected current. Switching tables, for different power factor angles, have been derived corresponding to different circuit topologies. Pulse width modulation (PWM) control method has been proposed. It is shown that only two devices need to be switched in any voltage sector there by resulting in a minimally switched PWM control reducing the switching loss. Current can be injected at any desired power factor angle. System works due to the presence of the closed loop. The high gain of the inverter together with that of the proportional controller ensures that the error between the reference and actual currents is small. Scheme has been simulated using SABER simulator