Solar Photovoltaic Electric System Protection. Prof. Brian Norton Dr. Sarah McCormack Mr. Kevin O Farrell. Ayda Esfandyari 28/02/2014

Transcription

1 Solar Photovoltaic Electric System Protection Prof. Brian Norton Dr. Sarah McCormack Mr. Kevin O Farrell Ayda Esfandyari 28/02/2014

2 Outline of the work Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Timelines Conclusion References Questions

3 Overview of Project Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Time-Lines Conclusion References Questions

4 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)

5 PV System High-Level Components PV System PV Module Balance of System Mounting Structure Power Conditioning unit Protection /Cables Storage Focus Protection

6 Introduction to Fault in PV Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Time-Lines Conclusion References Questions

7 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 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

8 Standards and limitations Different Standards, for Protection Requirements of PV Systems [1] I. IEC : Electrical Installations of Buildings II. III. IEC TS : Recommendations for Small Renewable Energy and Hybrid Systems for Rural Electrification IEC &2 Safety of Power Converters for Use in Photovoltaic Power Systems Different Voltage Levels according to IEC [1] IEC Voltage Range AC DC Defining Risk High Voltage >1000 Vrms >1500 V Electrical Arcing Low Voltage Vrms V Electrical Shock Extra-Low_voltage <50 Vrms <120 V Low Risk 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 )

9 Limitations ( continued) According to standard IEC NFPA 70 article 69(2014):[1] [2] Current protection practice 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

10 Specific Objective Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Time-Lines Conclusion Questions References

11 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. 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

12 State of the Art Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Time-Lines Conclusion References Questions

13 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, [4]Zhao, Ye, et al. "Line Line Fault Analysis and Protection Challenges in Solar Photovoltaic Arrays." Industrial Electronics, IEEE Transactions on 60.9 (2013): [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): [8]Luebke, Charles, et al. "Field test results of DC arc fault detection on residential and utility scale PV arrays." Photovoltaic Specialists Conference (PVSC), th IEEE. IEEE, 2011.

14 Methodology Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Time-Lines Conclusion References Questions

15 Flowchart Plan Comparing monitored data from experimental phase with simulation predicated results, to identify differences Experiment Prediction Isolation System Recovery Simulation Analyses of Problem Innovation/ Main contribution

16 Experimental Stage Experimental stage included number of rig experiments: I. Standard Steady-State Module Level ( Non Standard Test Condition ) II. III. Short_Circuit Fault Module Level ( Non_STC) Open_Circuit Fault Module Level ( Non_STC) IV. Standard Steady-State Cell Level (Standard Test Condition ) 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.

17 Flowchart Plan Experiment Prediction Isolation System Recovery Simulation Proof of Analysis Innovation/ Main contribution

18 Flowchart Plan Experiment Prediction Isolation System Recovery Simulation Proof of Anlysis Innovation/ Main contribution

19 Analyses Extra Small scale system Yes No Small scale system Fault prediction Examination/ fault occurrence validation Examination/ fault occurrence validation Fault prediction Optimal System Recovery Optimal System Recovery

20 Analyses Extra Small scale system Small scale system Fault prediction Examination/ fault occurrence validation Examination/ fault occurrence validation Fault prediction Optimal System Recovery Optimal System Recovery

21 Analyses Extra Small scale system Yes No Small scale system Fault prediction Examination/ fault occurrence validation Examination/ fault occurrence validation Fault prediction Optimal System Recovery Optimal System Recovery

22 Timelines Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Timelines Conclusion References Questions

23 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 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

24 Conclusion Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Time-Lines Conclusion References Questions

25 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

26 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)

27 Conclusion Overview of Project Introduction to Fault/Reliability Problems in PV Systems Specific Objective State of the Art Methodology Time-Lines Conclusion References Questions

28 References [1] 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, [4]Zhao, Ye, et al. "Line Line Fault Analysis and Protection Challenges in Solar Photovoltaic Arrays." Industrial Electronics, IEEE Transactions on 60.9 (2013): [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): [8]Luebke, Charles, et al. "Field test results of DC arc fault detection on residential and utility scale PV arrays." Photovoltaic Specialists Conference (PVSC), th IEEE. IEEE, 2011.

29 Thank you