Decentralised Master-slave Control for Series-cascaded AC Microgrid Integrating Solar Photovoltaic Generation

Microgrids formed by series-connected units provide an attractive way to integrate non-dispatchable low-voltage distributed generation (DG) such as solar photovoltaic (PV) panels to utility grid or microgrid, using DC-DC conversion stages with reduced boost voltage ratios. However, adequate power sharing and voltage regulation of a microgrid containing mixed dispatchable and non-dispatchable cascaded DGs demand new control approaches to achieve operational performance and reliability comparable to the conventional parallel-topology microgrid. This paper presents a series-cascaded microgrid architecture formed by a dispatchable master DG unit followed by a set of non-dispatchable slave PV units. A fully decentralised control scheme is proposed, which achieves autonomous power balancing and voltage regulation, ensures full utilisation of non-dispatchable generation units, and allows surplus power curtailment under light load conditions. The performance of the control approach is investigated by extensive switched simulations for various operating control modes and under different load scenarios.