Active Power Support and Coordination Control Strategy for Grid-Forming STATCOM Based on Model Predictive Control

With the increasing penetration of renewable energy, modern distribution networks exhibit pronounced "weak grid" characteristics, rendering them highly susceptible to transient voltage sags and active power imbalances. Traditional Static Synchronous Compensators (STATCOMs) are fundamentally restricted to purely reactive power compensation due to the lack of an active power buffer, while conventional proportional-integral (PI) controllers exhibit inherent dynamic delays during grid faults. To address these challenges, this paper proposes an active-power-supported multi-mode coordination control strategy for a grid-forming Energy Storage STATCOM (ES-STATCOM). Integrating a high-power-density supercapacitor (SC) into the DC link breaks the physical limitations of traditional devices, enabling simultaneous, decoupled four-quadrant power regulation. At the system level, a robust multi-mode power allocation logic navigates the boundaries between the inverter's maximum continuous overcurrent limits and the SC's state-of-charge (SOC) safety constraints. This ensures maximum emergency reactive power injection during faults while safely facilitating active power collaborative smoothing normally. At the algorithmic level, a discrete-time finite-control-set model predictive control (FCS-MPC) is implemented. By directly evaluating a cost function without a modulation stage, it effectively overcomes the dynamic delays of PI architectures. Extensive Hardware-in-the-Loop (HIL) real-time experiments validate that the proposed strategy achieves rapid, steady-state-error-free tracking of transient commands within a 10 ms window, maximizing transient support efficacy while rigorously guaranteeing equipment safety for power systems.