Cooperative Grid Forming Control Strategy for PV and BESS in an Isolated Microgrid

In the latest installment of our technical webinar series, Mo'ath Farraj presents on a novel strategy for managing DERs and battery storage in a microgrid.

Mo'ath Farraj received the B.Sc (Eng.) degree in Electrical Engineering from Philadelphia University, Jordan, in 2019. He recently completed his M.Sc degree at the University of Manitoba, Winnipeg, Canada and is currently working as an HVDC and power system studies engineer at Hatch Ltd. In his M.sc, he worked on developing a power management system for an isolated microgrid with the help of hardware in the loop simulation.

Summary:
Locally available solar PV energy alongside energy storage has emerged as a feasible renewable retrofit to the solely diesel-based remote off-grid power systems. In such areas, the grid-forming task is usually assigned to a dispatchable source such as a battery energy storage system (BESS), while the PV inverter operates as a grid-feeding unit due to the intermittent nature of PV power. The BESS unit, however, has a limited amount of energy and might sometimes fail to attain the preassigned voltage and frequency of the microgrid. Therefore, the capability of PV inverter to support the BESS unit in the grid-forming task in the absence of a diesel-based synchronous generator is critical when trying to reduce, optimize or replace the carbon-dependent generation capacity.
The intermittent nature of PV power imposes many constraints on operating the PV inverter as a gird supporting inverter while extracting the maximum available PV power. The operation of PV along BESS as grid-supporting inverter is governed under droop strategy to achieve load-sharing. However, this leads to inefficient sharing of energy between the BESS and the PV system, as the PV would operate at a lower level than its maximum power level.
This presentation outlines the control and operation of PV and BESS under grid-feeding and grid-forming modes applicable for isolated systems. It also presents an adaptive droop strategy for low voltage microgrids to achieve efficient parallel operation of PV and battery as grid forming inverters. The presented strategy facilitates maximum power point tracking (MPPT) operation and active power curtailment of PV to manage different operational scenarios by charging and discharging the battery. The simulation model of the considered isolated power system was built in the RTDS real-time simulation platform.