A Cost Effective Method of Reducing Total Harmonic Distortion (THD) in Single-Phase Boost Rectifier

Due to its simplicity, the discontinuous conduction mode boost rectifier is potentially the least expensive active line-harmonics reducing circuit. The line current however, shows considerable distortion when the peak input voltage is close to the output voltage. This paper proposes a simple, low-cost method to reduce the line harmonics. A periodic voltage signal is injected in the control circuit to vary the duty cycle of the boost switch within a line cycle so that the third-order harmonic of the input current is reduced and the THD is improved. The proposed technique eliminates the additional harmonic generator, phase detecting and phase-locking circuits, which is proposed in the literature. Instead we can utilize the output voltage of the rectifier in the boost converter in order to modulate the duty cycle of the boost switch. As a result, the injected signal is naturally synchronized with line current. Simulation and experimental results are presented to confirm the validity of the method.