Performance of low distortion 3-phase diode rectifiers using resonant harmonic correction networks

Resonant harmonic correction networks are presented that lower the line current harmonic distortion of three-phase diode rectifiers using a capacitor smoothed DC rail. The basic harmonic correction network consists of line inductors and capacitors connected in parallel with the rectifier. This structure injects resonant current into the AC supply that makes the line current waveshape more sinusoidal. Several modifications can be made to this basic structure that improves the rectifier performance and lowers the size of the line inductors. A twelve-pulse rectifier configuration can be used to achieve a line current distortion less than 5% using line inductors rated at around 0.14 p.u. Thyristor networks can be used to improve the rectifier power factor over a wide load range. Split resonant inductors with an IGBT switch can be used to decrease the size of the line inductors and to regulate the output DC-rail voltage over a wide load range and as compensation for fluctuating supply voltages. Experimental and simulated based performance analysis is presented that uses a per-unit system for the resonant impedance and resonant frequency