Prof. Brian Norton
Dr. Sarah McCormack
Mr. Kevin OFarrell
Solar Photovoltaic Electric System Protection
Ayda Esfandyari
28/02/2014
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
Outline of the work
Methodology
Timelines
Conclusion
References
Questions
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
Overview of Project
Methodology
Time-Lines
Conclusion
References
Questions
Overview of Project
Global Photovoltaic (PV) capacity has been growing exponentially
( Stand alone as well as grid connected applications )
Important efforts remain in terms of efficiency/performance, cost
and reliability
This project is part of SEAR (Solar Energy Application and
Research)
PV System High-Level Components
Balance of SystemPV Module
PV System
Mounting
Structure
Power
Conditioning
unit
Protection
/Cables
Storage
Protection
Focus
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
Introduction to Fault in PV
Methodology
Time-Lines
Conclusion
References
Questions
Relevant Definitions
Fault is a contingency/transient state, where system deviates from
its nominal state. ( Fault Start Time, Fault Duration, Fault Clearing Time)
Classical Electrical/Thermal Faults
Short Circuit, Open Circuit, Electrical Shocks, Insulation Fault, Reverse Current,
Overloading
Non Classical Faults Non Classical Faults
Arcing, Over Voltage/Surge, Shading
Fault in PV system can be split into A.C or D.C faults
The Protection device provides a form of insurance for electrical
components, by blocking and reducing the duration of disturbance
Standards and limitations
Different Standards, for Protection Requirements of PV Systems [1]
I. IEC 60364-7-712:2002-05 Electrical Installations of Buildings
II. IEC TS 62257-7-1:2006-12 Recommendations for Small Renewable Energy and Hybrid Systems for Rural Electrification
III. IEC 62109-1&2 Safety of Power Converters for Use in Photovoltaic Power Systems
Different Voltage Levels according to IEC [1]
Limitations
Considerations for electrical hazards in PV dominated by higher D.C voltage level i.e., Voltage
levels 120v D.C
Extra Low Voltage (ELV) level is assumed to pose low risk of threat , hence, it is generally
exempt from protection requirements ( Loose assumption which can lead to performance
degradation )
IEC Voltage Range AC DC Defining Risk
High Voltage >1000 Vrms >1500 V Electrical Arcing
Low Voltage 50-1000 Vrms 120-1500 V Electrical Shock
Extra-Low_voltage
Limitations ( continued)
According to standard IEC NFPA 70 article 69(2014):[1]
Hence, level of safety and careful measurements on the Low Voltage (LV) and
Medium Voltage (MV) level for PV protection does not seem to be sophisticated
[2] Current protection practice
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
Specific Objective
Methodology
Time-Lines
Conclusion
Questions
References
Objective
The objective of this research is :
To explore and evaluate the Necessary and Sufficient
protection strategies that currently exist or potentially
may prevail on Extra Low Voltage and Low Voltage
levels.levels.
The two conventional terms Necessary and Sufficient are used to
distinguish between basic and satisfactory level of protections
Note :
Protection scheme in ELV is quite underestimated.
Protection scheme in LV /MV is rather fragile
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
State of the Art
Methodology
Time-Lines
Conclusion
References
Questions
Current State of Research (Protection)
Monitoring and fault detection for hidden faults scenarios
[3]Zhao, Ye, et al. "Challenges to overcurrent protection devices under line-line faults in solar
photovoltaic arrays." Energy Conversion Congress and Exposition (ECCE), 2011 IEEE. IEEE, 2011.
[4]Zhao, Ye, et al. "LineLine Fault Analysis and Protection Challenges in Solar Photovoltaic
Arrays." Industrial Electronics, IEEE Transactions on 60.9 (2013): 3784-3795.
[5] Zhao, Ye, et al. "Outlier detection rules for fault detection in solar photovoltaic arrays." Applied
Power
[6]Xing Wu, 2011, Fault detection and diagnosis of Photovoltaic M.S. Thesis, University of Southern
California
[7]Silvestre, Santiago, Aissa Chouder, and Engin Karatepe. "Automatic fault detection in grid
connected PV systems." Solar Energy 94 (2013): 119-127.
[8]Luebke, Charles, et al. "Field test results of DC arc fault detection on residential and utility scale
PV arrays." Photovoltaic Specialists Conference (PVSC), 2011 37th IEEE. IEEE, 2011.
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
Methodology
Methodology
Time-Lines
Conclusion
References
Questions
Flowchart Plan
Comparing monitored data from experimental phase with simulation predicated results, to identify differences
Experiment
Prediction Isolation
System
Recovery
Simulation
Innovation/ Main
contribution
Analyses of
Problem
Experimental Stage
Experimental stage included number of rig experiments:
I. Standard Steady-State Module Level ( Non Standard Test Condition )
II. Short_Circuit Fault Module Level ( Non_STC)
III. Open_Circuit Fault Module Level ( Non_STC)
IV. Standard Steady-State Cell Level (Standard Test Condition )IV.
V. Short_Circuit Fault Cell Level (STC)
VI. Open_Circuit Fault Cell Level (STC)
Hence, module standard conditions will be presented from cell test results
At this phase of study, no protection element/device/agent is installed
Choosing the fine/the most appropriate sampling time to capture Electrical
Characteristics / measurement variables.
Flowchart Plan
Experiment
Prediction Isolation
System
Recovery
Simulation
Innovation/ Main
contribution
Proof of
Analysis
Flowchart Plan
Experiment
Prediction Isolation
System
Recovery
Simulation
Innovation/ Main
contribution
Proof of
Anlysis
Analyses
YesNo
Fault prediction
Extra Small scale
systemSmall scale system
Examination/ fault
occurrence validation
Fault prediction
Fault prediction
Examination/ fault
occurrence validation
Optimal
System
Recovery
Optimal
System
Recovery
Analyses
Fault prediction
Extra Small scale
systemSmall scale system
Examination/ fault
occurrence validation
Fault prediction
Fault prediction
Examination/ fault
occurrence validation
Optimal
System
Recovery
Optimal
System
Recovery
Analyses
YesNo
Fault prediction
Extra Small scale
systemSmall scale system
Examination/ fault
occurrence validation
Fault prediction
Fault prediction
Examination/ fault
occurrence validation
Optimal
System
Recovery
Optimal
System
Recovery
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
Timelines
Methodology
Timelines
Conclusion
References
Questions
Timelines and Workprograms
WP1: Literature Review/Thesis
WP2: Estimation of Electrical Characteristics using Experimental Rigs
WP3: Assessment of Measurement Variables by Means of Simulation
WP4: Evaluation of System Responses, Protection Mechanism and
Reactions
WP5: PV System Recovery/Restoration WP5: PV System Recovery/Restoration
Workpackages Mar(14)
Aug(14)
Sep(14)-
Feb(15
Mar(15)
Aug(15)
Sep(15)-
Feb(16)
Mar(16)
Aug(16)
Sep(16)-
Feb(17)
Mar(17)
Aug(17)
Sep(17)-
Feb(18)
Wp1 Wp1 Wp1 Wp1 Wp1 Wp1 Wp1 Wp1 Wp1
Wp2 Wp2 Wp2
Wp3 Wp3 Wp3
Wp4 Wp4 Wp4
Wp5 Wp5 Wp5 Wp5
D D/P1 D/P2 D/P3 D/P4/P5
M Transfer Confirmation Thesis
Years 1 1 2 2 3 3 4 4
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
Conclusion
Methodology
Time-Lines
Conclusion
References
Questions
Conclusion
ELV voltage level is treated to be inherently safe, hence, Module power is too
low to cause serious damage ???
There is still potential for fault /power loss and efficiency degradation in ELV (Ohmic losses ,Maximum Power Point Tracking ( MPPT),DC/AC conversion efficiencies, Operating above reference
temperature at module level, Mismatch and non-uniform temperature and irradiance in PV generator, Fault induced lower
irradiance )
Scope for diagnostic analyses, to identify the accountable cause of problem
(ELV)
Level of safety and careful measurements on the Low Voltage (LV) level for PV
protection does not seem to be as sophisticated
These issues all point to room for a novel approach, to provide a
holistic supply security and safety study on the DC side of PV systems
Conclusion
Fault predication and isolation is the current focus of academic
research and industry
PV system restoration has the potential to be explored
PV System Recovery Challenges
System restoration is mostly performed on the standard High and Medium Voltage
level systems(classical power system restoration) !!!!
Formulation of optimal decision based problem ,which is subject
to sets of constraint variables ( time, cost, etc)
Overview of Project
Introduction to Fault/Reliability Problems in PV Systems
Specific Objective
State of the Art
Conclusion
Methodology
Time-Lines
Conclusion
References
Questions
References
[1]www.iec.ch , Accessed Feb 2014
[2] Sizing fuses for Photovoltaic Systems per the National Electrical Code, 2012, Mersen
[3]Zhao, Ye, et al. "Challenges to overcurrent protection devices under line-line faults in solar photovoltaic arrays." Energy
Conversion Congress and Exposition (ECCE), 2011 IEEE. IEEE, 2011.
[4]Zhao, Ye, et al. "LineLine Fault Analysis and Protection Challenges in Solar Photovoltaic Arrays." Industrial Electronics, IEEE
Transactions on 60.9 (2013): 3784-3795.
[5] Zhao, Ye, et al. "Outlier detection rules for fault detection in solar photovoltaic arrays." Applied Power
[6]Xing Wu, 2011, Fault detection and diagnosis of Photovoltaic M.S. Thesis, University of Southern California
[7]Silvestre, Santiago, Aissa Chouder, and Engin Karatepe. "Automatic fault detection in grid connected PV systems." Solar Energy
94 (2013): 119-127.
[8]Luebke, Charles, et al. "Field test results of DC arc fault detection on residential and utility scale PV arrays." Photovoltaic
Specialists Conference (PVSC), 2011 37th IEEE. IEEE, 2011.
Thank you