On-line measurement on stability margin of DC distributed power system

In a DC distributed power system, the system level small-signal stability is determined by the minor loop gain, which is an impedance ratio Z/sub o//Z/sub i/ between source and load power modules. This paper proposes a practical approach to measure the stability margin of the minor loop gain Z/sub o//Z/sub i/ online. By injecting small-signal external perturbation current i/spl circ//sub p/ into the DC bus and measuring the magnitude of the load side response current i/spl circ//sub L/, the system stability margin can be figured out. Due to its simplicity in principle and implementation, this proposed measurement is useful for both stability analysis in system design and stability monitor in system operation.