Distributed energy resources (DER), such as photovoltaic systems and storage have noticeably increased during the last decade in many countries. Residential DERs could be aggregated and dispatched to offer different system-level services, such as frequency/voltage control. However, as DER penetration increases, distribution network constraints cannot be ignored as their aggregated dispatch can result in voltage violations and/or congestions. Therefore, in the future, the distribution system operator (DSO) will need to check DER aggregator proposals when aiming to participate in a systemlevel service provision. If issues are anticipated by the DSO, smaller volumes of services will have to be implemented by aggregators, communicating, and acting over DER setpoints. This work, describes a realistic lab implementation of an aggregator acting over remote hybrid inverters (PV+storage), using internet and the modbus protocol. This will be later integrated with a real-time network simulator (hardware in the loop) representing the network run by the DSO.