Modelling and control of an interface power converter for the operation of small diesel gen-sets in grid-connected and stand-alone modes

This paper presents the modelling and control design steps of a two-stage static conversion structure used as interface to integrate a diesel generator set into a secondary distribution network. In order to guarantee that the inverter works within the PWM linear range, a boost converter is used to increase the DC voltage level. The proposed structure allows two operation modes, connected to the AC mains or isolated. In the isolated mode the interface converter may be controlled as grid-forming or grid-conditioning (active power filter). The inverter current controllers are designed in the synchronous reference frame together with multiple integrators in order to effectively track non-sinusoidal currents. The stability analysis is performed through the Nyquist plot. Experimental results obtained with a 5.5 kW diesel generator set are presented to validate the proposed system operation and control strategies.