A three-phase buck-type rectifier features a step-down ac-dc conversion function, which is considered as a prominent solution for electric vehicle chargers and telecommunication systems integrated to the grid above 380 V line to line. However, traditional solutions for those applications employ cascaded architectures with an ac-dc boost-type stage and a dc-dc buck-type stage, which may suffer from high switching losses and large dc-link capacitor volume. To relieve this issue, a straightforward carrier-based two-phase-clamped discontinuous pulsewidth modulation (DPWM) strategy with generalized zero-sequence voltage injection is proposed in this article for the commonly employed cascaded circuit. This method can stop the switching actions in the front-end stage during two-third of the grid period, which can yield to the best switching loss reduction. The operations of the front- and back-end converter stages become highly coupled to each other, which reduces the size requirement of the capacitor in the dc link. Therefore, the equivalent circuit behaves as a quasi-two-stage buck-type rectifier allowing an enhancement of the system power density by improving power conversion efficiency and by reducing the volume of passive components and heat sink. The proposed carrier-based two-phase-clamped DPWM strategy is described, analyzed, validated, and compared with different pulsewidth modulation methods on PLECS-based simulation and a 5-kW prototype.
- buck-type rectifier
- discontinuous pulsewidth modulation (DPWM)
- Phase modulation
- Pulse width modulation
- Switching loss
- Voltage control
- zero-sequence voltage injection