Proportional-resonant controller of high power 400Hz inverter in stationary frame

In high power middle frequency 400Hz/115V Inverters, the ratio of device switching frequency to output voltage fundamental frequency is low, so conventional control techniques are hard to promise good waveform quality. The single-phase inverter based on cascaded topology with two H-Bridge units reduces the harmonic content of output voltage. The three-phase inverter consisting of three single-phase independent-controlling inverters by shifting phase 120° each other is able to eliminate completely the output voltage distortion due to unbalanced loads. Fundamental proportional-resonant (PR) controller adopted in the outer loop of multiple-feedback loop control and the 3
^rd
, 5
^th
and 7
^th
harmonics PR controller in the inner loop can regulate effectively ac signal, eliminate steady-state errors and compensate the 3
^rd
, 5
^th
and 7
^th
harmonics in stationary frame. Analysis and simulation on a 300kVA middle frequency inverter model are presented. The simulation results verified the effectiveness of the proposed scheme at heavy nonlinear and unbalanced load condition.