Stability Problems in Designing Aggregated and Distributed Systems of Secondary Power Supplies

In this paper, we show that, when operating in the stand-alone mode, self-oscillating modes, due to the interaction of subsystems, are possible in aggregated (composite, complex) power supplies and distributed power supply systems (DPSs) that use the “bus” approach and consist of stable modules with large margins of stability in amplitude and phase of loopback gain of negative feedback. The self-excitation of the system is shown to be due to the complex nature of the input and output impedances and the negative active (real) component of the input impedance of the output DPS subsystem. The negative nature of the active component of the input impedance of the output (load) subsystem with stabilized output voltage, i.e., with negative feedback, is due to the falling nature of its input current–voltage characteristic. The design of aggregated devices and DPSs is shown to require a systematic approach, provided that the properties and interactions of subsystems are taken into account.