ANALYSIS & CONTROL FOR PV SOLAR INTEGRATED WITH GRID FORMING POWER RESERVES

Abstract

It presents a grid-forming control (GFC) scheme for two-stage photovoltaic (PV) systems that maintains
power reserves by operating below the maximum power point (MPP). The PV plant in GFC mode behaves like a
voltage source that supports the grid during disturbances in full or limited grid-forming mode as per the reserve
availability. This is a model-free method that avoids the estimation of MPP power in real-time commonly done in the
literature, which makes it simpler and more reliable. The proposed control also features an enhanced current limitation
scheme that guarantees containment of the current overshoots during faults, which is not trivial in voltage-sourced
GFC inverters. A thorough investigation is done, exploring various generation mixtures of synchronous machines
(SM), GFC, and grid-following (GFL) inverters, and all common disturbances, e.g., load change, faults, and irradiance
transients. The results show very favorable dynamic performance by the GFC inverters, far superior to GFL inverters
and directly comparable to SMs. It is found that replacing SMs with GFC inverters may improve the frequency profile
and terminal voltage during disturbances, despite losing out in the mechanical inertia and the strict inverter overcurrent
limits. Index Terms— Ancillary services, current limitation, grid forming control, grid support, inverter, maximum
power point, power reserves, renewable integration, solar photovoltaic (PV).