Abstract
This paper presents a novel three-phase current source rectifier (CSR) for AC/DC step-down voltage conversion to reduce voltage and current stress. The proposed converter features an asymmetrical connection between upper and lower arms compared with conventional CSRs, but has the same number of devices. With the proposed asymmetrical structure and modified space vector pulse width modulation (SVPWM) scheme, half of transistors only need to withstand half of the line-to-line voltage rather than the full line-to-line voltage, and its DC link current can be shared by multiple switches in freewheeling periods. Therefore, it is able to bring about a significant reduction in voltage and current stress, allowing for an improvement in the converter without additional cost. The topological structure, operation principles, and comparative analysis are specifically presented. Finally, an experimental prototype is built up to verify the performance of the proposed converter.
Highlights
The proposed current source rectifier (CSR) features an asymmetrical topological structure and would have reduced stress on semiconductor devices. It means that half of transistors on low voltage stress can be achieved in power factor correction (PFC) operation, and the proposed converter could have a higher efficiency at a low modulation index due to the multiple freewheeling paths
Similar to three-phase voltage source rectifier (VSR), on the upper arms are added to the current path of the proposed CSR
In order to operate at unity power factor, a compensation angle should be adopted in the CSR system
Summary
The three-phase CSR, known as the buck-type rectifier, is widely used in AC/DC conversion systems, such as fast electric vehicle chargers, energy storage devices, communication power supplies, adjustable speed drives, wind power generation systems, high power applications, etc. [1,2,3,4,5,6,7,8]. CSR [18], swiss-type CSR [19], delta-type CSR [20], split freewheeling diode CSR [21], etc Another kind of isolated CSR is achieved with a high-frequency transformer [22,23,24,25,26,27]. The isolated CSR is not suitable for most of industrial applications Both CSRs could obtain a sinusoidal input current and constant DC output voltage, as well as high stress on semiconductor devices, which is not expected in practice. The proposed CSR features an asymmetrical topological structure and would have reduced stress on semiconductor devices It means that half of transistors on low voltage stress can be achieved in PFC operation, and the proposed converter could have a higher efficiency at a low modulation index due to the multiple freewheeling paths. All theoretical analysis and experimental results show that the proposed CSR is a suitable topology for step-down voltage applications
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