Revised stability criteria for cascaded DC-DC converters in space applications

The Middlebrook's criteria is used in the ECSS-E-ST -20C (European Cooperation for Space Standardization - Electrical and Electronic) to guarantee the stability of cascaded power systems. It is worth noticing that the non-compliance to Middlebrook's criterion does not represent a necessary condition for stability, therefore when not satisfied, additional analysis might be necessary to check the stability margins. It is however a very conservative approach. Other less conservative methods have been proposed for the interconnection of feedback controlled DC/DC converters. Among others, a revised criterion is considered in this paper and different study-cases are analyzed to demonstrate the typical situations that a power engineer is facing with cascaded DC-DC power supplies.