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This paper proposes the improved topology and control strategy of three-phase cascaded bridgeless rectifier (CBR) suitable to serve as the rectifier stage for a medium/high voltage multilevel converter. Compared with traditional H-bridge based multilevel rectifiers, the proposed topology adopts much fewer fully-controlled devices, which greatly reduces the control complexity, thus increasing the system...
This paper presents a new unidirectional cascaded bridgeless multilevel rectifier (CBR) well suited for serving as the rectifier stage of a transformerless cascaded multilevel converter. Compared to a traditional cascaded H-bridge rectifier, the proposed CBR utilizes fewer fully controlled switching devices by replacing the fully controlled H-bridge modules with bridgeless PFC modules, thus simplifying...
This article has proposed a control strategy for balancing the capacitors' voltage of cascaded H-bridge rectifier. The working principle of cascaded H-bridge rectifier has been described, as well as the balancing boundary condition of capacitors' voltage. Then, the dual modulation curves control strategy has been proposed for balancing the capacitors' voltage in dc side of the rectifier. Furthermore,...
Studies have shown that for a datacenter DC power distribution system has higher efficiency and reliability than a traditional AC power distribution system. DC distribution system has two voltage standards, 48V and 380V. Most of the studies show that 380V DC distribution is more promising than the 48V DC distribution. This paper presents a quantitative comparison and evaluation for both the 48V DC...
In this paper, the relations among the active power distribution, modulation wave and unbalanced loads range are analyzed. A maximum unbalanced loads range is proposed by modifying modulation waveforms under the unity power factor. And a modified staircase modulation, which is easy to realize, is proposed for a single-phase cascaded H-bridge multilevel rectifier to extend the range of unbalanced loads...
The control strategy of cascaded rectifier which is used as the first stage of a new generation cascaded line-frequency transformerless power converter is discussed in this paper. The circuit model of cascaded rectifier stage is simplified, and the mathematical model of cascaded rectifier stage is set up based on Single-Phase Rotating Frame. A balance strategy for DC link capacitor voltage of each...
The traditional direct power control (DPC) strategy exits the problems that the switching frequency is not fixed, the sampling frequency is high and so on. To combat these problems, a control system of improved virtual-flux control strategy with DPC (VF-DPC) is proposed in the paper. In order to overcome the problem that switching frequency is not fixed, hysteretic controller and switching table are...
PWM rectifier control system is designed, where predictive current control in two static reference frames is as current control method, voltage space vector pulse width modulation is pulse width modulation method, and traditional PI regulator is adopted as DC voltage control. This method has an advantage of quick response of hysteresis current control, the frequency of apparatus is fixed, and control...
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