Maximum constant boost approach for controlling quasi-Z-source-based interlinking converters in hybrid AC-DC microgrids

This study presents the mathematical modelling and control design methodology of bidirectional quasi-Z-source inverters (qZSIs) for interlinking converter application in hybrid AC-DC microgrids. The proposed control scheme provides the maximum constant boost (MCB) control capability for the qZSI in both grid-connected and islanded modes of operation even in the presence of unbalanced AC loads. The proposed approach maintains the MCB without any additional control loop for regulating the voltage of the DC-side capacitor of the qZSI. This is done by determining the shoot through duty cycle of the qZSI based on the inverter modulation index. Moreover, maintaining the MCB condition, the proposed control scheme provides a high stability margin for the qZSI network. The effectiveness of the proposed method is demonstrated through simulation studies conducted on a typical AC-DC hybrid microgrid in MATLAB/Simulink environment for both islanded and grid-connected modes of operation.