Impedance-Based VSC Unit Commitment with STATCOM Support under High IBG Penetration

TL;DR

This paper presents a mixed-integer second-order cone programming framework for unit commitment that incorporates frequency and voltage stability constraints, including STATCOM support, to improve grid security and reduce costs under high inverter-based generation.

Contribution

It extends existing models by integrating STATCOM reactive power support into the UC optimization for enhanced voltage and frequency stability in high IBG scenarios.

Findings

Incorporating STATCOM improves voltage security and dispatch feasibility.

The joint UC with STATCOM reduces operating costs.

The framework maintains frequency-nadir constraints under high IBG penetration.

Abstract

The large-scale replacement of synchronous machines with inverter-based generation (IBG) introduces critical challenges to both voltage and frequency stability. This work builds on a mixed-integer second-order cone programming (MISOCP) framework that co-optimizes unit commitment (UC) model which embeds frequency-nadir constraints through synthetic inertia (SI) dispatch and an SOC voltage stability boundary for IBG buses. The formulation extends by modeling a STATCOM as a reactive-power decision variable in the same MISOCP model. A modified IEEE 30-bus system is used to assess three scheduling strategies: (i) baseline UC with SI only, (ii) voltage-stability-constrained (VSC) UC with SI, and (iii) the joint UC with SI and reactive power support from IBGs. The impact of incorporating a 30~MVAr STATCOM at a weak grid location near the IBG buses is investigated. Simulation results show that the proposed framework enhances voltage security, maintains frequency-nadir compliance, and reduces operating cost, while STATCOM integration further improves dispatch feasibility under high IBG.