Event-Triggering Power Reserve Control for Grid-Connected PV Systems

The still increasing penetration of renewable energy demands more from the distributed generations (DGs), e.g., grid-friendly PV systems, to maintain the entire system stability. One of the requirements is the power reserve, where PV systems should regulate the output power flexibly instead of solely being a generating unit. To achieve the power reserve, this paper proposes an event-triggering power reserve control (PRC) for three-phase two-stage PV systems. It works periodically with two operating modes - the maximum power mode (MPM) and the power reserve mode (PRM). The MPM is at the beginning of every PRC cycle, where the maximum power point tracking (MPPT) is performed to track the maximum power point (MPP). Once the MPP is tracked, the system subsequently switches to the PRM, which directly regulates the PV output power to the given reference (after the power reserve). A modified monotonic Power-Voltage (P-V) curve is used in the PRM to make the system operates at the left steady-state point with respect to the MPP for higher robustness. Moreover, considering the power impulses during the switching between the MPM and the PRM, power impulse damping control (PIDC) is designed to damp the transient energy by the DC-link capacitors. Simulation results validate the proposed PRC method.