Controlled Operation of the Islanded Portion of the International Council on Large Electric Systems (CIGRE) Low Voltage Distribution Network

Ghullam Mustafa Bhutto,Ehsan Ali,Claus Leth Bak

doi:10.3390/en10071021

Abstract

In islanding, a portion of the power network, comprised of the loads and distributed generation (DG) units, is isolated from the rest of the power grid and forms a micro grid (MG). In this condition, it becomes essential for the islanded MG to operate in a stable and controlled manner by providing ancillary services. When the MG is cut off from the main grid, the islanding must be detected by the DG units. In this condition it is essential that one of the controllers should be switched to the voltage-frequency (VF) control mode. In islanding, the network loses it slack reference and this reference is established by a VF controller. The voltage and the frequency of the islanded MG deviate when disconnected from the transmission grid and these deviations are caused by the load-generation imbalance. The voltage and the frequency of the islanded MG can be restored to the permissible limits if the desired/exceeded amount of active and reactive power is injected/absorbed by the locally available sources in islanded MG. This paper proposes a control strategy which can compensate the voltage and the frequency deviations in the islanded portion of the International Council on Large Electric Systems (CIGRE) low voltage distribution network by using advanced power electronics devices such as STATCOMs) for Photovoltaic (PV) Units and Battery Energy Storage Systems (BESS) STATCOMs (for battery units). The selection of the VF controller for the most suitable DG unit of this test network is also presented in this paper, and the effectiveness of the controllers is verified by presenting simulation results using DIgSILENT (DIgSILENT GmbH, Gomaringen, Germany) power factory software version 15.0.

Highlights

Research in the field of intentional islanding operation of distribution systems has been increased day by day due to economic and technical reasons [1,2]
Islanding is a generic term which describes the condition where a section of a power network supplied by Distributed Generation (DG) units is separated from the main grid
The controllability of Micro Grid (MG) may be obtained if the desired amount of active and reactive power support reactive power in the islanding, the MG voltage increases and vice versa

Summary

Introduction

Research in the field of intentional islanding operation of distribution systems has been increased day by day due to economic and technical reasons [1,2]. The controllability of MG may be obtained if the desired amount of active and reactive power support reactive power in the islanding, the MG voltage increases and vice versa This can be networks achievedisiftoan appropriate control system is developed. The development of the control system for DG units in the islanded mode is different fromisthat of controllability of MG may be obtained if the desired amount of active and reactive power support the grid connected mode. The novelty of this paper is that it describes the clear concepts of establishing a VF controller in the islanded portion of the CIGRE low voltage distribution network and presents a clear idea how to assign VF controller and to which of the existing DG units in the network. The establishment of VF controller in the islanded portion of CIGRE low voltage distribution network in case DG units are integrated into the islanded MG.

Control Strategy for the Islanding

The system from

Simulation Results

Conclusions