Three Electrolytic Capacitor Elimination Schemes in Quasi-Z-Source Converter: Theory and Experimental Verification

Electrolytic capacitors (ECs) are important components in power converters. However, their lifespan is much shorter than other components, and their sizes increase greatly with larger capacitance. As a result, ECs limit power converters’ lifespans and contribute to larger sizes. This study proposes three schemes of eliminating ECs in the quasi-Z-source DC-DC converter (QZSC). In scheme A, a non-electrolytic capacitor quasi-Z-source DC-DC converter (NEC-A-QZSC) is realized to minimize the converter size and with low-cost design, but has high voltage ripples. The schemes B and C are then proposed to add a low-pass filter to different voltage ports on QZSC to reduce output voltage ripples with the same boost capability, hence achieving a better performance and stability. For proof of concept, theoretical analysis with small-signal models, simulation studies and prototype experiments of the proposed NEC-QZSC converter are presented. Simulation and experimental results well agree with the theoretical analysis. The NEC-QZSCs proposed in the schemes B and C achieve small converter sizes while improving the voltage conversion performance, realizing better nonlinear response, and having high economic advantages.