Abstract

To resolve the protection issues caused by high penetration of distributed energy resources, this paper proposes an efficient protection scheme for microgrids based on the autocorrelation of three-phase current envelopes. The proposed strategy uses a squaring and low-pass filtering approach for evaluating the envelope of the current signal. Then, the variance of the autocorrelation function is used to extract the hidden information of the distorted envelope to detect the fault signatures in the microgrid. Furthermore, the reactive power is used for determining the fault direction. The performance of the proposed protection scheme was verified on a standard medium-voltage microgrid by performing simulations in the MATLAB/Simulink environment (Version: R2017b). The proposed scheme was shown to be easy to implement and have good performance under looped and radial configuration for both grid-connected and islanded operation modes. The simulation results showed that the scheme could not only detect, locate, classify, and isolate various types of short-circuit faults effectively but also provide backup protection in case of primary protection failure.

Highlights

  • The utilization of distributed energy resources (DERs) to generate electric power around the world is increasing owing to the increasing cost and gradual depletion of fossil fuels, and the considerably rising demands for clean power and greenhouse gas emission reduction [1,2]

  • We propose a microgrid protection scheme based on the autocorrelation function (ACF) of a three-phase current envelope

  • This paper presents a microgrid protection strategy that uses the ACF of the three-phase current envelope

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Summary

Introduction

The utilization of distributed energy resources (DERs) to generate electric power around the world is increasing owing to the increasing cost and gradual depletion of fossil fuels, and the considerably rising demands for clean power and greenhouse gas emission reduction [1,2]. Energies 2020, 13, 2350 with the high penetration of distributed generators (DGs) in the microgrid and the ability of the microgrid to switch across grid-connected and islanded modes, the amplitude and direction of fault currents vary according to the system’s irregularities [7] In both low and medium-voltage generation systems, the bidirectional power arising from the generators and loads flows through the protective devices in a microgrid. Reference [20] proposed an online adaptive multistage definite time overcurrent scheme for ungrounded distribution systems with DGs. The authors in [21] proposed a comprehensive protection strategy employing MBRs for the dependable and safe operation of an islanded microgrid.

Proposed
Fault Detection Unit
Squaring and Low-Pass Filtering and Envelope Detection
Autocorrelation Function
Threshold Setting
Fault Direction Unit
Reactive Power
Fault Zone Identification Unit
Main and Backup Protection
Study Cases
Study Case 1
StudyRelay
Study Case 2
3: Primary
10. Backup
Conclusions

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