Sinusoidal Input Current Discontinuous Conduction Mode Control of the VIENNA Rectifier

During light load conditions unidirectional power factor correction rectifiers, such as the VIENNA rectifier, enter discontinuous conduction mode, causing the relationship between average half-bridge voltage and duty cycle to become nonlinear and synchronously sampled current measurements not equaling the switching period average. Combined, these measurement and actuation errors result in distorted input currents at light load if no additional measures are taken. This work presents a control scheme that leads to low total harmonic distortion of the input currents in discontinuous conduction mode without relying on current measurements. The analytic expressions for the duty cycles and the threshold between discontinuous and continuous conduction mode are derived, the capability of supplying asymmetric loads is investigated and the effect on the noise spectrum relevant for the electromagnetic interference filter design is studied. Measurements of efficiency, total harmonic distortion, and conducted electromagnetic interference in discontinuous and continuous conduction mode are obtained on a 65 kW prototype operating at 290 to 530 V line-to-line RMS mains voltage range and supplying 800 V dc output voltage. The prototype, which is optimized for pulse load applications, achieves a power density of 9.56 kW/dm
³
(157 W/in
³
) and 97.2 % efficiency at full load using 650 V Si insulated gate bipolar transistor (IGBTs) with 28 kHz switching frequency.