Component-Minimized Buck-Boost Voltage Source Inverters

This paper presents the design of buck-boost B4 inverters that can be derived from either Cuk- or SEPIC-derived buck-boost B6 inverters. Unlike traditional inverters, the integration of front-end voltage boost circuitry and inverter circuitry allows it to perform buck-boost voltage inversion. In order to form a distinct neutral potential in the corresponding voltage boost circuitry for correct B4 inverter operation, necessary modifications are derived step by step. The resulted dc networks with symmetrical placement of passive components allow complete charging and equal energy distribution between capacitors. Modulation wise, the proposed buck-boost B4 inverters can be controlled using a carefully designed carrier-based pulse-width modulation (PWM) scheme that will always ensure balanced three- phase outputs as desired, while simultaneously achieving minimal voltage stress across semiconductors. Besides the advantage of reduced active components, buck-boost B4 inverters use a little more passive components when compared with buck-boost B6 inverters, which would allow a selectable tradeoff in practice. Moreover, analysis for discontinuous conduction mode of inductor current reveals the additional voltage relationship between dc input and ac output which is beyond the expectation when continuous inductor current is assumed. These theoretical findings, together with the inverter practicality, have been confirmed in Matlab/PLECS simulations and experimentally using laboratory implemented inverter prototypes.