A power decoupling method with small capacitance requirement based on single-phase quasi-Z-source inverter for DC microgrid applications

This paper proposes a power decoupling method based on single-phase quasi-Z-source inverter (SPQZSI) for DC microgrid applications. Single-phase inverter would cause harmonic issues especially voltage ripple in DC microgrid because of low-frequency (100/120Hz) power ripple. Non-linear load or source would generate other harmonic on the common DC link as well. In order to achieve power decoupling, large electrolytic capacitor is required and connected to DC link in H-bridge inverters. However, electrolytic capacitor would affect the power density, reliability and lifetime of DC microgrid. Quasi-Z-source inverter is utilized instead for capacitance reduction. In terms of low-frequency ripple control with SPQZSI, an effective control method is necessary to regulate the current/voltage of both AC port and DC port. The theoretical analysis about capacitance requirement with power decoupling in SPQZSI is done first. Next, an advanced control method based on generalised predictive control is proposed to decouple low-frequency power ripple. The corresponding control law and predictor are designed as well. Experimental results with 500W prototype verify the stability, feasibility and superior performance of the proposed power decoupling method based on SPQZSI.