Comparison of two different configurations of independent Active Power Decoupling networks in Active-Front-End Impedance Source Inverters

In recent literature, the Active-Front-End Impedance Source Inverters (AFE-ISIs), such as Switched Boost Inverter, Current-Fed Switched Inverter, etc., are well-researched owing to their significantly better EMI immunity and buck-boost capability, which are desirable advantages over conventional Voltage Source Inverter (VSI). However, single-phase AFE-ISIs inevitably encounter the low-frequency ripple (LFR) problem, which remains relatively less explored. The LFR problem forces AFE-ISIs to compromise power density as bulky passive elements become essential to limit the LFR problem and retain the sinusoidal nature of the output voltage waveform. To tackle the LFR problem in single-phase VSI, active power decoupling (APD) networks are extensively explored, among which the independent APD networks (IAPDNs) are particularly advantageous solutions as these networks operate independently of the inverter operation. The most common IAPDNs are buck, boost and buck-boost-type, which are generally connected across the dc-link in a VSI. However, this configuration is unsuitable for AFE-ISIs owing to their topological difference and operating principle compared to the VSI. As an alternative configuration, the IAPDNs can be connected across the dc-link capacitor of AFE-ISIs. This paper compares both configurations to illustrate the advantages of the latter configuration with the help of theoretical analysis and simulation results. The effectiveness of the boost-type IAPDN-integrated SBI with the preferred configuration is verified with experimental results.