Battery Enhanced PV Microinverter with Ancillary Service Capabilities

Worldwide agreements towards mitigating the climate change effects have driven a growing penetration of renewable energy sources (RES) into electricity grids and the increasing decommission of large-scale fossil-fuel based generating units. Nevertheless, these RES additions are usually characterized by presenting low-inertia and high variability and intermittency, while the receding fossil-fuel plants were capable of providing inertia and grid support in terms of ancillary services. Ancillary service markets are usually dominated by large- and medium-scale systems, including renewable power plants, however excluding small-scale PV systems, typically installed at the distribution-grid level. This work presents a two-stage PV microinverter, where the dc-link has been replaced by a battery, allowing the microinverter to offer ancillary services. The proposal also takes advantage of the lower power rating requirements of partial power converters (PPCs), replacing the conventional full-power step-up dc-dc converter by a step-up PPC. Simulation results of the system under nominal operation (performing maximum power point tracking) and providing ancillary services are presented. The results show the capability of PV microinverters to participate in the ancillary-service market, due to the potential of residential power generation systems.