A novel, robust, harmonic injection method for single-switch, three-phase, discontinuous-conduction-mode boost rectifiers

This paper describes a new, robust, low-cost, harmonic-injection method for single-switch, three-phase, discontinuous-conduction-mode (DCM) boost rectifiers. In the proposed method, a periodic voltage is injected in the control circuit to vary the duty cycle of the rectifier switch within a line cycle so that the 5/sup th/-order harmonic of the input current is reduced to meet the IEC555-2 requirement. Since the injected voltage signal, which is proportional to the inverted AC component of the rectified three-phase line-to-line input voltages, is employed, the injected duty-cycle variations are naturally synchronized with the three-phase, line-to-neutral input voltages. In addition, the injected harmonic signal naturally contains desirable higher-order harmonics, such as 6/sup th/, 12/sup th/, 18/sup th/, etc., which are more effective in improving THDs than harmonic-injection methods based on the 6/sup th/-order harmonic only.