A Single-Phase Rectifier Having Two Independent Voltage Outputs With Reduced Fundamental Frequency Voltage Ripples

Half-bridge rectifiers are able to provide two voltage outputs, which offers three voltage levels, but the two voltage outputs depend on each other and also on system parameters. Moreover, the two voltage outputs contain large ripples because the currents following through the split capacitors contain significant fundamental-frequency components. In this paper, after analyzing the drawbacks of half-bridge rectifiers in detail, an independently controlled neutral leg is added to conventional half-bridge rectifiers to address these drawbacks. Furthermore, the associated decoupling control strategies are proposed. The rectification leg from the conventional half-bridge rectifier is controlled to maintain the dc-bus voltage and to draw a clean sinusoidal current that is in phase with the supply voltage. The neutral leg is controlled with a PI-repetitive controller to regulate one voltage output and also to provide the current path for any dc and/or fundamental-frequency components. As a result, the two voltage outputs are regulated independently and are robust against system parameters. The output voltage ripples are also reduced, and hence, the required capacitance to achieve the same level of voltage ripples is reduced. Experimental results are provided to validate the performance of the proposed single-phase rectifiers having two independent voltage outputs.