Abstract
The three-phase buck rectifier (3ph-BR) is suitable for applications where a voltage step-down function is required. In this paper, an improved 3ph-BR topology is proposed to reduce the voltage stress on the transistors. The freewheeling diode in the conventional topology is split into two diodes in series and the input neutral point is connected to the common point of the two diodes. With the proposed topology and the corresponding modified modulation scheme, the transistors only need to withstand the input phase voltage instead of the line-to-line voltage, bringing about the significant reduction of voltage stress. The proposed topology enables a more cost-efficient and flexible selection of the transistors. Experimental results have verified the validity of the modified topology and associated modulation scheme.
Highlights
The conventional 3ph-BR topology is shown in Fig. 1, which consists of three legs and one freewheeling diode
If bidirectional power flow is required, the diodes in these topologies can be replaced with transistors with the same voltage rating, while the proposed improvement is still applicable to the transistors on the forward current path
It was widely taken for granted that the voltage rating of all the devices in the three-phase buck rectifier should be selected based on the amplitude of input line-to-line voltages
Summary
The conventional 3ph-BR topology is shown in Fig. 1, which consists of three legs and one freewheeling diode. Considering a typical margin (around 50%), voltage rating of devices must be at least 900V or higher. IGBTs can achieve higher voltage rating (upwards of 1200V), but their switching performance is poorer and devices cannot be paralleled to improve efficiency. SiC MOSFETs can reach higher voltage rating with superior switching performance, but they are still expensive compared with comparable Si devices. This makes the conventional topology less attractive compared with its competitor: the newly developed SWISS rectifier (SR) [14]-[17]. A circuit improvement is proposed to reduce the voltage stress on transistors in the conventional 3ph-BR topology.
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