Hybrid Reactive Power Compensation Sizing for Grid-Code Compliance of a 120 MW Wind Farm: A Load-Flow Comparison of Passive and STATCOM-Based Configurations

Utility-scale wind farms must provide at the point of connection (PoC) a reactive power range that is often wider than the aggregated capability of their turbines. A previous assessment of a 120 MW doubly fed induction generator wind farm connected to the Moroccan 225 kV network identified an absorption deficit at low active power. The present paper does not revisit that diagnosis; it contributes a reproducible and cross-validated procedure for sizing and verifying the remedial compensation. Seven passive and hybrid (STATCOM-based) configurations are evaluated against a +48/−36 Mvar requirement for PoC voltages of 0.9–1.087 pu, first on 616 PowerFactory load-flow scenarios and then with an independent Newton–Raphson model built from the complete collector data, which reproduces the PowerFactory results with a mean absolute error of 0.07 Mvar when the on-load tap changers (OLTCs) are active. The independent model extends the verification to 23,331 operating points (1% active-power and 0.01 pu voltage steps), non-uniform turbine dispatch, equipment tolerances, transformer loading limits, the continuity of the reactive power range across switching states and harmonic resonance screening. Covering the 39.0 Mvar deficit at zero output requires at least 37.8 Mvar of 33 kV reactors with OLTC action and 40.0 Mvar without it, because the reactor output falls with the square of the collector voltage. An 8 Mvar STATCOM with 3 × 10 Mvar reactors falls 0.7 Mvar short, whereas a 10 Mvar STATCOM with 3 × 10.5 Mvar reactors, or 3 × 11 Mvar reactors, satisfies the requirement at all evaluated steady-state operating points, with worst-case margins of 2.2–2.5 Mvar that shrink to 0.6–0.9 Mvar for a −5% reactor tolerance. At the voltage extremes the OLTCs reach their end positions, but all 33 kV and turbine voltages remain within their continuous operating ranges, and limiting the turbine transformers to their rating still leaves an absorption margin of at least 45 Mvar at high output. Relative to the existing capacitor-bank states, the added reactors and STATCOM introduce no new low-order resonance in the screening model. The procedure is transferable to other plants subject to wide-range reactive power requirements.