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 fifth-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 sixth, twelfth, eighteenth, etc., which are more effective in improving total harmonic distortions (THDs) than harmonic-injection methods based on the sixth-order harmonic only.