Monitoring the stability of DC distributed power systems

Abstract

In a DC distributed power system, the system level small-signal stability is determined by the minor loop gain, which is an impedance ratio of Z/sub o//Z/sub i/ between the source and load power modules. This paper proposes a practical method to monitor the stability margin of DC distributed power systems. By injecting a small-signal external perturbation current i/spl circ//sub p/ into the DC bus and measuring the response current i/spl circ//sub s/ of the source module/subsystem, the distance between the minor loop gain Z/sub o//Z/sub i/ and the (-1,0) point in the S-plane can be figured out as S(/spl omega/)=|i/spl circ//sub p/(j/spl omega/)/i/spl circ//sub s/(j/spl omega/)|. Consequently, the system stability margin can be monitored by checking whether the inequality S(j/spl omega/)> 1/2 is valid or not. Both simulation and experimental results demonstrate the effectiveness of the proposed method.