This paper presents a new family of high efficiency DC/AC grid-tied inverter with a wide variation of input DC voltage. It is a "Boost in Boost, Buck in Buck" inverter, meaning that only one power stage works at high frequency in order to achieve minimum switching loss. The minimum voltage drop of the filtering inductor in the power loop is achieved to reduce the conduction power loss in both "Boost" and "Buck" mode. The principle of operation is demonstrated through the analysis on the equivalent circuits of a "half-bridge" single-phase inverter. The theoretical analysis shows that when input DC voltage is larger than the magnitude of the AC voltage, it is a Voltage Source Inverter (VSI), and on the contrary it is Current Source Inverter (CSI) in the other mode. A 220 V/50 Hz/ 2000 W prototype has been constructed. Simulations and experiments show it has a good control and system performance.Keywords-Voltage source inverter, current source inverter, LCL filter, CL filter, Buck in Buck, Boost in Boost, efficiency. 0885-8993 (c)

 Abstract-The single-phase power converter topologies evolving of PV applications are still including the passive filter，like LCLor LLCL-filter. Compared with the LCL-filter, the total inductance of LLCL-filter can be reduced a lot. However, due to the resonant inductor in series with the bypass capacitor, the Differential Mode (DM) Electromagnetic Interference (EMI) noise attenuation of an LLCL-filter based grid-tied inverter declines. Conventionally, a capacitor was inserted in parallel with the LC resonant circuit branch of LLCL-filter to suppress the DM EMI noise. In order to achieve a small value of capacitor as well as to minimize the additional reactive power, a novel simple DM EMI suppressor for the LLCL-filter based system is proposed. The characters of two kinds of DM EMI suppressor are analyzed and compared in detail.Simulations and experiments on a 0.5 kW, 110 V / 50 Hz singlephase grid-tied inverter prototype are accomplished to confirm the analysis.

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Owing to less conduction and switching power losses, the recently proposed Aalborg inverter has high efficiency within a wide range of input DC voltage for single-phase DC/AC power conversion. In theory, the conduction power losses can be further decreased, if an LLCL-filter is adopted instead of an LCL-filter for a voltage source inverter, mainly due to the reduced inductance. The Aalborg inverter shows the characteristic of a current source inverter, when working in the 'boost' state. Whether the LLCL-filter can meet the control requirement of this type inverter needs to be further explored. In this study, the small signal analysis for the modified-LLCL-filter-based Aalborg inverter is addressed. Through the modelling, it can be proven that compared with the LCL-filter, the modified-LLCL-filter causes no extra control challenge for the Aalborg inverter, and therefore more inductance in the power loop can be safely saved as well as a complete smaller filter size. A 220 V/50 Hz, 2000 W prototype is used to demonstrate the theoretical analysis.

Abstract-The Aalborg Inverter is a new type of high efficient DC/AC grid-tied inverter, where the input DC voltage can vary in a wide range. Compared with the LCL-filter, the LLCL-filter can save the total inductance for the conventional voltage source inverter. In this paper, an LLCL-filter based Aalborg Inverter is proposed and its character is illustrated through the small signal analysis in both "Buck" and "Buck-Boost" mode. From the modeling, it can be seen that the resonant inductor in the capacitor loop has not brought extra control difficulties, whereas more inductance in the power loop can be saved. Simulation and experiments are carried out to verify the analysis and the design through an 220 V/50 Hz, 2000 W prototype.