Add to ORKGA model of an integrated modelocked ring laser is presented. This model is used to analyse the behaviour of a 26GHz mode-locked ring laser fabricated with activepassive integration. The semiconductor amplifier and the saturable absorber are described using rate equations. The bandwidth limitation is simulated by a digital filter. The laser is modelled by segmenting the ring in parts. This allows the inclusion of intracavity reflections in the model. Self-starting, self-pulsating and modelocking operation have been simulated in a bi-directional mode. Our experimental and theoretical results are compared and discussed