A Decentralized Approach for Voltage Control by Multiple Distributed Energy Resources

The design of a decentralized control scheme is presented which is capable of counteracting voltage variations and offering the ancillary service of voltage regulation to the Distribution Network (DN) by acting on reactive and active power injections of Distributed Energy Resources (DERs). The design is based on a complete dynamic Multi-Input Multi-Output (MIMO) model of the distribution system with different types of DERs interfaced to the DN by inverters. Each DER is equipped with a state-feedback controller and two standard regulators of type PI and I, which realize the dynamic voltage adjustment, ensure null regulation error of voltage and active power at the Point of Common Coupling (PCC) and guarantee robust stability. This control objective is achieved without communication links among the local controllers and in presence of parameters uncertainty affecting the MIMO model. Finally, the proposed approach is validated by dynamic simulations on the IEEE 123 node test feeder with 15 additional DERs of three different types in presence of different scenarios of the distribution system, inaccuracy of the DN line parameters and voltage sags.