Constant power loads and negative impedance instability in sea and undersea vehicles: statement of the problem and comprehensive large-signal solution

Power electronic converters are usually loaded by passive loads or combinations of passive elements and voltage and current sources. However, there is an emerging vehicular system configuration where converters are loaded by power converters and a better model for the load is a constant power model. This converter operation appears in multi-converter applications such as advanced sea and undersea vehicles where a main converter has as loads a set of converters operating in closed-loop with tight output voltage regulation. This set of converters present at the input terminals a dynamic behavior similar to a constant power load (CPL) for a range of input voltages and a frequency span that ranges from DC up to the bandwidth of the converters. The primary goal of this paper is the development and extension of a technique for large-signal analysis of power electronic converters operating with constant power loads in sea and undersea vehicles using a phase plane analysis. This proposed approach could be used to present advantages and limitations of different controllers and, based on that analysis, define the selection and synthesis of controllers to achieve the required performance and robustness of the system.