New Five Level Resonant DC/DC Buck-Boost Converter

Multilevel resonant DC/DC converters are getting more popular being applied in UPS systems, multi-level inverter drives, DC microgrids or electrical vehicles. They have several advantages, such as zero voltage and zero current switching, reduced switching losses, improved performance and high efficiency. This paper introduces a new, four channel resonant Buck-Boost converter topology. It consists of four output channels providing equivalent or different voltage levels which can be both higher or lower than the voltages of the two input channels. The symmetrical operation of the converter is examined under steady state conditions, in discontinuous current conduction mode. One goal of the paper is to analyse the effect of independent control variables on each output during symmetrical operation. These variables are the switching angle alpha[degrees], capacitor peak voltage V*(c) [pu] (being dependent parameters) and switching frequency f*(s) [pu] (being independent of the previous two). Control parameter f*(s) is usually kept constant (f*(s) = 1), as lowering of this variable degrades the dynamical performance, while increasing the output voltage ripple. Both alpha and V*(c) are proper control parameters, as they are monotonically increasing with the controlled parameter, which in our case is the output voltage V*(o) [pu].