Single-switch constant-power equalization charger based on multi-stacked buck-boost converters for series-connected supercapacitors in satellite power systems

Supercapacitors (SCs) have potential to be good alternatives to batteries in satellite power systems because they not only have a longer life but also reduce the mass of photovoltaic arrays when they are charged using a constant-power (CP) charging scheme. In this paper, we propose singles-switch CP equalization chargers using multi-stacked buck-boost converters. In addition to the single-switch operations, the equalization chargers operating in the discontinuous conduction mode (DCM) do not require feedback control, and hence, the feedback loop can be eliminated. Operations under voltage-balanced and voltage-imbalanced conditions were mathematically generalized. An experimental charge test was performed for four SCs connected in series. The SC(s) with the lowest voltage was (were) preferentially charged by the equalization charger. The voltage imbalance was gradually eliminated, and finally, all SCs were charged to a uniform voltage level.