Recent research has proved that, the local reactive power control laws considered to solve voltage stability issue might lead to voltage instability. For this reason, the current paper proposes an approach to study voltage stability of multiple distributed generators in distribution feeders. The methodology relies on the construction of an equivalent state space model of the continuous system. A simulation based on MATLAB of the proposed approach to a real medium-voltage 26 buses network with 3 distributed generators reveals unstable operating situations of the network and helps to design a set of measurement filters to ensure system stability.