Synthesis of Low-Voltage Minimum Switch-Count DC Bus Second-Harmonic Hybrid Filters

Abstract

Active Power Decoupling (APD) has emerged as an attractive technique to eliminate large DC bus filter capacitors in single-phase power conversion. For space-constrained circuits with reliable operation, DC capacitor elimination is an advantage as long as the added component count, rating, and control complexities do not outweigh the benefits. The present work focuses on adding a minimum number of active components of low voltage ratings to alleviate bulk DC bus filter capacitors from single-phase power converters. Thus, the driving circuits and control efforts also get proportionally scaled down while yielding the benefits of bulk capacitor reduction. Apart from the minimum component count, the use of low-voltage devices ensures reduced switching and conduction losses, improving the active filter efficiency. A generalized topology synthesis framework is presented that yields a family of low voltage, minimum switch-count APD filter derivatives with identical operational objectives. The control and operational trade-offs of the derived filter topologies are compared and a design-oriented ripple analysis is performed to maximize capacitor utilization. The significant attributes of the derived filters are compared with the state-of-the-art active and hybrid filters. The operations of the synthesized three unique topologies are experimentally validated using laboratory hardware at a 500 W power level. Above 90% reduction in the DC bus second-harmonic ripple is achieved by the action of the proposed filters. With the proposed control, the boost-based SC-BOHF topology exhibits better filtering performance than SC-BUHF and SC-BBHF.