Penetration and control of grid-forming (GFM) inverter in LFC of an enhanced IEEE 9-Bus interconnected power system

Abstract

Load-frequency-control (LFC) is employed for frequency stability and balanced power flow among control-areas. Inverters are becoming critical assets in modern power networks with increasing renewable energy. As these inverter-based resources prevail, the system inertia decreases, leading to potential frequency instability problems. Grid-forming (GFM) inverter development and applications are gaining significant attraction because of their ability to maintain quality power-grid operations. GFM inverter, acting as a voltage-source-converter, adjusts its output frequency by contributing a portion of the load change to reduce the frequency deviations. The virtual synchronous generator (VSG) control mechanism for GFM is implemented in this work. A two-area interconnected power system model emulating an enhanced IEEE 9-Bus system is developed and simulated in MATLAB-Simulink® for analysis. Secondary controllers are applied in each LFC and GFM-loop of the proposed LFC-GFM system with a magnetotactic-bacteria-optimization (MBO) algorithm for simultaneously tuning these parameters. The proposed control strategy’s effectiveness is verified by comparing simulation results with the basic LFC system under varying inverter penetration levels. The simulated dynamic responses verify the efficacy of the controlled penetration of the GFM inverter in the proposed LFC-GFM system with enhanced damping characteristics, improving small-signal stability and reducing settling time by 43.46% and frequency deviation by 55.5%.