Modeling of Grid-Connected PV–Storage System with Frequency Support Capability Under Multi-Mode Control Strategy

This study examines coordinated active-power allocation in a DC-coupled photovoltaic (PV) and energy storage system (ESS) with a virtual synchronous generator (VSG) inverter. A rule-based supervisor selects PV maximum power point tracking (MPPT) or the voltage control mode (VCM) and ESS charging, discharging or standby using the available PV power, state of charge (SOC) and categorical scheduling inputs. The implementation combines bounded sampled adaptive inertia, a frequency deadband, measured-current guards and a supercapacitor DC link regulator. Simulations record all five modes and SOC-dependent discharge inhibition under a prescribed source-frequency disturbance. Matched comparisons quantify the scheduling role of PV curtailment, the transient trade-offs of adaptive inertia and the DC link response with the supercapacitor branch retained or removed. Recorded mode states and transient metrics characterize switching behavior. A conditional bound is derived for the reduced frequency state, with parameter and discretization checks defining its evaluation scope. The results characterize five-mode coordination and its response limits in the specified simulation benchmark.