An instability phenomenon may occur in DC electrical systems due to undesirable source load interaction and the behavior of power electronic loads that act as a constant power load. The present study focuses on DC electrical systems associated with constant power behavior. The phenomenon occurs such that each converter has its own internal control function for its output voltage regulation. The converter tends to draw a constant power which therefore produces negative incremental input impedance within its bandwidth. An active damping technique is proposed to improve the stability of a DC electrical system consisted of photovoltaic arrays, an LC filter and a constant power load. The active damping network was controlled to behave as a small-signal effective damping resistor over a DC network so that any instability in the DC bus will be reduced and eliminated. This technique eliminates the oscillations produced by the constant power load. MATLAB/SIMULINK modeling and simulation are used to confirm the validity of the proposed technique. (C) 2012 Elsevier Ltd. All rights reserved.