A reliable islanding identification mechanism for DC microgrid using PCC transient signal

Abstract The islanding detection is a major problem for both AC and DC Microgrids. Failure to do so may result in problems such as system instability, increased non-detection zone, out-of-phase reclosing, personnel safety, and power quality deterioration. To address this issue, this paper presents a reliable island identification method for DC Microgrids that employs a Cumulative Sum of Rate of change of Voltage (CSROCOV) to reduce the non-recognition region. The proposed islanding protection scheme employs point of common coupling (PCC) transient signal to detect islands events. The voltage, power, and current sampling are accumulated from the PCC of the distributed generation terminals. The proposed scheme detects islanding in three test cases with varying power mismatching conditions, while non-islanding events are classified as capacitor switching and faults. The system is modelled and simulated in the MATLAB/Simulink environment, then islanding conditions are applied by turning off the main circuit breaker. Simulation results are presented to verify the methodology under different test cases. The robustness of the proposed scheme is also validated against measurement noise.

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Differential Evolution-Based Overcurrent Protection for DC Microgrids

Energies ◽

10.3390/en14165026 ◽

2021 ◽

Vol 14 (16) ◽

pp. 5026

Author(s):

Miao Li ◽

Daming Zhang ◽

Shibo Lu ◽

Xiuhui Tang ◽

Toan Phung

Keyword(s):

Differential Evolution ◽

Case Studies ◽

Load Condition ◽

System Size ◽

Performance Criterion ◽

Dc Microgrid ◽

Dc Microgrids ◽

Protection Scheme ◽

De Algorithm ◽

Overcurrent Protection

DC microgrids have advantages over AC microgrids in terms of system efficiency, cost, and system size. However, a well-designed overcurrent protection approach for DC microgrids remains a challenge. Recognizing this, this paper presents a novel differential evolution (DE) based protection framework for DC microgrids. First, a simplified DC microgrid model is adopted to provide the analytical basis of the DE algorithm. The simplified model does not sacrifice performance criterion in steady-state simulation, which is verified through extensive simulation studies. A DE-based novel overcurrent protection scheme is then proposed to protect the DC microgrid. This DE method provides an innovative way to calculate the maximum line current, which can be used for the overcurrent protection threshold setting and the relay coordination time setting. The detailed load condition and solar irradiance for each bus can be obtained by proposed DE-based method. Finally, extensive case studies involving faults at different locations are performed to validate the proposed strategy’s effectiveness. The expandability of the proposed DE-based overcurrent protection framework has been confirmed by further case studies in seven bus mesh systems.

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A Protection Scheme for Standard Equipment to Avoid Harmful Random Large Current

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.834-836.1642 ◽

2013 ◽

Vol 834-836 ◽

pp. 1642-1647

Author(s):

Shu Zhe Qi ◽

Wei Han ◽

Song Bin Zhou ◽

Chang Li ◽

Ke Jia Huang

Keyword(s):

Transient State ◽

Transient Signal ◽

Test Results ◽

Danger Signal ◽

Standard Equipment ◽

Protection Scheme ◽

Large Current ◽

Current Sampling ◽

Short Time

In the process of detecting and calibrating for power equipments, it appears a phenomenon that standard equipment is damaged by harmful random large current from tested equipment. This danger signal mainly occurs in the transient state of tested equipment, i.e., in a short time after starting to output new set current. This paper proposes a method for protecting standard equipment to eliminate damage caused by random large current. Its content mainly describes one of the key parts of this scheme including accurately sampling and transient signal removing intelligently in details. Design the related current sampling circuit, test results show that the resolution of circuit can reach to 10mA, which satisfies the work well.

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Integrated Control and Protection Architecture for Islanded PV-Battery DC Microgrids: Design, Analysis and Experimental Verification

Applied Sciences ◽

10.3390/app10248847 ◽

2020 ◽

Vol 10 (24) ◽

pp. 8847

Author(s):

Ali Abdali ◽

Kazem Mazlumi ◽

Josep M. Guerrero

Keyword(s):

Fault Detection ◽

Integrated Control ◽

Storage System ◽

Energy Storage System ◽

Detection Algorithm ◽

Dc Microgrid ◽

Dc Microgrids ◽

Protection Scheme ◽

Bus Voltage ◽

Battery Energy

Direct current (dc) microgrids have gained significant interest in research due to dc generation/storage technologies—such as photovoltaics (PV) and batteries—increasing performance and reducing in cost. However, proper protection and control systems are critical in order to make dc microgrids feasible. This paper aims to propose a novel integrated control and protection scheme by using the state-dependent Riccati equation (SDRE) method for PV-battery based islanded dc microgrids. The dc microgrid under study consists of photovoltaic (PV) generation, a battery energy storage system (BESS), a capacitor bank and a dc load. The aims of this study are fast fault detection and voltage control of the dc load bus. To do so, the SDRE observer-controller—a nonlinear mathematical model—is employed to model the operation of the dc microgrid. Simulation results show that the proposed SDRE method is effective for fault detection and robust against external disturbances, resulting in it being capable of controlling the dc load bus voltage during disturbances. Finally, the dc microgrid and its proposed protection scheme are implemented in an experimental testbed prototype to verify the fault detection algorithm feasibility. The experimental results indicate that the SDRE scheme can effectively detect faults in a few milliseconds.

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Development of New Protection Scheme in DC Microgrid Using Wavelet Transform

Energies ◽

10.3390/en15010283 ◽

2022 ◽

Vol 15 (1) ◽

pp. 283

Author(s):

Hun-Chul Seo

Keyword(s):

Wavelet Transform ◽

Low Voltage ◽

Rapid Development ◽

Circuit Breaker ◽

Stable Operation ◽

Fault Current ◽

Pv System ◽

Dc Microgrid ◽

Protection Scheme ◽

Protection Method

The demand for a low voltage direct current (LVDC) microgrid is increasing by the increase of DC-based digital loads and renewable resources and the rapid development of power electronics technology. For the stable operation of an LVDC microgrid, it is necessary to develop a protection method. In this paper, the new protection scheme considering the fault section is proposed using wavelet transform (WT) in an LVDC microgrid. The fault sections are classified into DC side of the alternating current (AC)/DC converter, DC/DC converter connected to photovoltaic (PV) system, DC line, and DC bus. The characteristics of fault current at each fault section are analyzed. Based on these analyses, the new protection scheme including the fault section estimation is proposed using WT. The proposed scheme estimates the fault section using the detail component after performing WT and sends the trip signal to each circuit breaker according to the fault section. The proposed protection scheme is verified through various simulations according to the fault region and fault current using electromagnetic transient program (EMTP)/ATPDraw and MATLAB. The simulation results show that the fault section is accurately determined, and the corresponding circuit breaker (CB) operations are performed.

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A Bus-Sectionalized Hybrid AC/DC Microgrid: Concept, Control Paradigm, and Implementation

Energies ◽

10.3390/en14123508 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3508

Author(s):

Jing Li ◽

Hongda Cai ◽

Pengcheng Yang ◽

Wei Wei

Keyword(s):

Hierarchical Control ◽

Mode Switching ◽

Stable Operation ◽

Service Reliability ◽

Test Results ◽

Dc Microgrid ◽

Dc Microgrids ◽

Operation Modes ◽

Control Paradigm ◽

Operational Data

In the last several years, the coordination control of hybrid AC/DC microgrids (HMGs) has been gaining increasingly more attention. However, most of these discussions are focused on single-bus HMGs whose AC or DC bus is not sectionalized by AC or DC breakers. Compared with these single-bus HMGs, the bus-sectionalized HMG has more flexible topologies, more diverse operation modes, and consequently higher service reliability. However, meanwhile, these benefits also bring challenges to the stable operation of bus-sectionalized HMGs, particularly for mode switching. Relying on the national HMG demonstrative project in Shaoxing, China, this paper makes efforts to present the hierarchical control paradigm of a typical bus-sectionalized HMG toward standardization. The test results demonstrate that the proposed system provides seamless switching and uninterrupted power supply without controller reconfiguration among different operation modes. The operational data are also brought forth and analyzed to provide significant and useful experiences for designing and developing similar HMGs in the future.

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A Cosine Similarity Based Centralized Protection Scheme for DC Microgrids

IEEE Journal of Emerging and Selected Topics in Power Electronics ◽

10.1109/jestpe.2021.3060587 ◽

2021 ◽

pp. 1-1

Author(s):

Rabindra Mohanty ◽

Subham Sahoo ◽

Ashok Kumar Pradhan ◽

Frede Blaabjerg

Keyword(s):

Cosine Similarity ◽

Dc Microgrids ◽

Protection Scheme

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Fault Detection in DC Microgrids Using Short-Time Fourier Transform

Energies ◽

10.3390/en14020277 ◽

2021 ◽

Vol 14 (2) ◽

pp. 277

Author(s):

Ivan Grcić ◽

Hrvoje Pandžić ◽

Damir Novosel

Keyword(s):

Fourier Transform ◽

Fault Detection ◽

Operating Conditions ◽

Time Signal ◽

Short Time Fourier Transform ◽

Dc Microgrid ◽

Protection Scheme ◽

Simulink Model ◽

Battery Energy ◽

Short Time

Fault detection in microgrids presents a strong technical challenge due to the dynamic operating conditions. Changing the power generation and load impacts the current magnitude and direction, which has an adverse effect on the microgrid protection scheme. To address this problem, this paper addresses a field-transform-based fault detection method immune to the microgrid conditions. The faults are simulated via a Matlab/Simulink model of the grid-connected photovoltaics-based DC microgrid with battery energy storage. Short-time Fourier transform is applied to the fault time signal to obtain a frequency spectrum. Selected spectrum features are then provided to a number of intelligent classifiers. The classifiers’ scores were evaluated using the F1-score metric. Most classifiers proved to be reliable as their performance score was above 90%.

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Protection Scheme for DC Microgrid Distribution System

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.614-615.1661 ◽

2012 ◽

Vol 614-615 ◽

pp. 1661-1665

Author(s):

Ling Hui Deng ◽

Zhi Xin Wang ◽

Jian Min Duan

Keyword(s):

Distribution System ◽

Cost Efficiency ◽

Power Flow ◽

Low Voltage ◽

Dc Microgrid ◽

Protection Scheme ◽

High Level ◽

Bidirectional Power Flow ◽

Efficiency And Reliability ◽

Laboratory Prototype

The low voltage DC (LVDC) distribution system is a new concept and a promising technology to be used in the future smart distribution system having high level cost-efficiency and reliability. In this paper, a low-voltage (LV) DC microgrid protection system design is proposed. Usually, an LVDC microgrid must be connected to an ac grid through converters with bidirectional power flow and, therefore, a different protection scheme is needed. This paper describes practical protection solutions for the LVDC network and an LVDC system laboratory prototype is being experimentally tested by MATLAB/SIMULINK. The results show that it is possible to use available devices to protect such a system. But other problems may arise which needs further study.

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