Primary cabin voltage and reactive power control by distributed generators

The paper deals with control structures and functionalities contributing to the distribution grid smartness in the presence of distributed generators (DG). The Primary Cabin (PC) hosting DG is analyzed assuming a voltage control scheme that includes the Transformer (TR) with On-Load Tap Changer (OLTC), but also generators and FACTS allowing their reactive power remote control. Therefore more and contemporary closed loops controls operate on the same voltage variable or on the strictly linked reactive power. These combined efforts require a proper coordination among the operating control loops having different dynamic performances. Promising proposals of alternative coordinated PC controls, including the reactive power flow between the HV and MV bus-bars, are presented. They are substantially aimed to achieve effective automatic regulations by simple and practical solutions. The considered control schemes take into account different PC operating conditions including the islanded network covered by proper functional variant. The considered PC regulator is also provided with automation functionalities operating a timely and proper switching of capacitor banks and shunt reactors when remotely controllable.