Control for Grid-Connected and Intentional Islanding Operations of Distributed Power Generation

TLDR

Intentional islanding isolates a microgrid with load and distributed generation, requiring the system to continue supplying power, which is normally achieved by DG inverters operating in constant‑current mode. The study proposes a control strategy that enables both grid‑connected and intentional‑islanding operations, including an intelligent load‑shedding algorithm for islanding and a synchronization algorithm for grid reconnection. When isolated, DG inverters detect islanding and switch to voltage‑control mode to maintain constant voltage to the local load, implementing the proposed control strategy.

Abstract

Intentional islanding describes the condition in which a microgrid or a portion of the power grid, which consists of a load and a distributed generation (DG) system, is isolated from the remainder of the utility system. In this situation, it is important for the microgrid to continue to provide adequate power to the load. Under normal operation, each DG inverter system in the microgrid usually works in constant current control mode in order to provide a preset power to the main grid. When the microgrid is cut off from the main grid, each DG inverter system must detect this islanding situation and must switch to a voltage control mode. In this mode, the microgrid will provide a constant voltage to the local load. This paper describes a control strategy that is used to implement grid-connected and intentional-islanding operations of distributed power generation. This paper proposes an intelligent load-shedding algorithm for intentional islanding and an algorithm of synchronization for grid reconnection.