Ramp-rate control strategy for distributed PV-ESS AC-stacked inverter architecture

Ramp-rate control smooths out sudden photovoltaic (PV) output variations by charging and discharging electricity through an energy storage system (ESS). This paper describes the ramp-rate control strategy adapted to the new modular panel-level grid-connected single-phase PV inverter architecture, distributed PV-ESS AC-stacked inverter, and its control capability. The modular inverter members including PV inverters and ESS are connected in series and regulating each member's output in decentralized manner. To minimize the communication requirements between the PV inverters and the ESS, the ESS utilizes the local AC string current measurement to detect PV output variations for the ramp-rate control. Feasibility and effectiveness of proposed control scheme have been demonstrated and verified through a controller hardware-in-the-loop (CHIL) test.