Revisiting stability criteria for DC power distribution systems based on power balance

Single-input-multiple-load converter systems sharing a common input DC voltage bus is becoming popular in DC power distribution. Due to the convenience of using conventional voltage-source systems for connecting a common bus voltage with multiple downstream loads, the same configuration is often adopted for current-source systems, where design optimization can be achieved without an intermediate (bus) voltage regulator. However, the stability of such cascaded current-source systems is still relatively unexplored or incomplete, though the associated basic circuit theory has been well established. In this paper, steady-state operating points are obtained by applying power balance between the current-source output converter and the downstream converters. The incremental change of the input power versus the input impedance of the downstream converters is derived. The stability of such current-source converter systems is re-visited using an impedance-based approach. A general set of impedance-based stability criteria is developed and experimentally verified by a DC bus system consisting of a current source output converter and two PWM power converters.