A Practical Protection Coordination Strategy Applied to Secondary and Facility Microgrids

Dae-Geun Jin,Jung-Sung Park,Jong-Chan Choi,Dong-Jun Won,Woo-Kyu Chae,Hak-Ju Lee

doi:10.3390/en5093248

Abstract

In a conventional distribution system, protection algorithms are designed to operate on a unidirectional high fault-current level. In a microgrid, a fault current from distributed generation (DG) may bring about a relay malfunction because of the bidirectional and relatively small fault current. Therefore, the conventional protection scheme is not applicable to microgrids and a new protection method must be developed. In this paper, two protection coordination algorithms which can be applied for facility and secondary microgrids are proposed, respectively. The proposed protection algorithms eliminate faults not by the EMS signal but by directional relays. Moreover, this makes the algorithms flexible regardless of the types and numbers of DG. The proposed protection algorithms were simulated at the KEPCO RI Microgrid Demonstration Site.

Highlights

With high oil prices and climate change causing serious environmental concerns, distributed generation (DG) using renewable energy is becoming necessary
A protection coordination algorithm applied to a facility microgrid (i.e., Zone B) and a protection coordination algorithm applied to secondary microgrids (i.e., Zones A and B) were proposed and verified
In the case of Zone A with the protection algorithm, the microgrid is shut down when a fault occurs at the feeder with a controllable DG

Summary

Introduction

With high oil prices and climate change causing serious environmental concerns, distributed generation (DG) using renewable energy is becoming necessary. Many countries have implemented regional energy businesses and pilot projects on diffusion of renewable energy as a national energy policy. Such conditions have led to the spread of microgrids. A microgrid is a small-scale power grid which includes various DGs and loads. It is usually connected to the utility grid at a point which is called a point of common coupling (PCC). A microgrid behaves as a fully controllable load. A microgrid is usually operated in the grid connected mode, and it can be operated in island mode [1,2,3,4]

Methods

Results

Conclusion