Dual buck based power decoupling circuit for single phase inverter/rectifier

Single phase rectifiers and inverters are inherently subject to double-line frequency ripple power, at both the ac and dc sides, which has adverse effects on the overall system performance. Normally a bulky capacitor is placed at the dc side of the circuit to prevent this ripple power ripple from reaching the dc source. This approach results in low power density and reliability issues. As a result, active power decoupling methods have been proposed such that the total capacitance required can be orders of magnitude smaller. This paper proposed a new power decoupling circuit, which is composed of two separate buck converters operating in each half cycle and two split dc-link capacitors. The dc link capacitors can be used to store ripple power while supporting transient power to the main output. The capacitance needed is reduced largely by allowing high voltage fluctuation on capacitors, while the dc link voltage can be controlled with small fluctuation. The dc link capacitors can be fully charged and discharged with full energy utilization. The added power decoupling module does not need dead time, and totally eliminates the shoot through concerns, which could enhance the system reliability. Another advantage of the proposed power decoupling method is that its control is independent with that of the main power stage. Modulation and control strategy are proposed for the power decoupling circuit. The operating principles together with parameters design are discussed in detail. Both simulation and experimental results prove the effectiveness of this method.