Tools for field testing

Transcription

1 Tools for field testing Gianluca Corbellini - SUPSI October 6 th

2 Agenda 1. Introducing SUPSI 2. Context of PV testing 3. State of the art field testing 4. Procedure for inverter testing 5. Procedure for strings testing 6. New tools developed inside Performance Plus 7. What s next? 2

3 Located in Lugano (Ticino) 4500 students 30y+ experience in PV Outdoor test stand Swiss PV Module Test Center Swiss BIPV Competence Centre 3

4 Context of PV testing 180+ GWp of PV worldwide - 90 in EU Several plants suffer under performance Grid parity requires high quality (1GWp) Need for accurate PV testing: Improve bankability Guarantee energy yield, promised performance and economic return Prevent failures on components 4

5 Root causes of under performance Flaws in design Potential Induced Degradation Insulation Microcracks in cells Hot spots Module delamination TCO corrosion Soiling losses Inverter issues 5

6 System testing Sequential component testing to detect root cause of the low performance MODULE STRING INVERTER SYSTEM

7 Devices for field testing Monitoring Visual Inspection Thermal camera I-V tracer DC and AC PR tester Insulation tester 7

8 New tools developed inside Performance Plus Procedure for system/inverter testing Procedure for string testing Tool for inverter analysis Tool for modules/strings analysis 8

9 Inverter check procedure 1/2 Optical inspection of inverter Check inverter error log files Under performance from monitoring Deviation found Error found? Y Y Mechanical failure Follow failure indication Degradation failure VDC, IDC measurements Unstable MPPT? Y DC controller Cin effect (switching ripple) Multiple Maxima Algorithm runaway PV modules String level V/I measurements Incorrect MPPT? Y 9

10 Inverter check procedure 2/2 VAC, IAC, cos(phi) measurement Grid disturbancies? Y AC controller Output filter Grid quality PAC, PDC comparison Low conversion Efficiency? Y Stable energy losses Variable energy losses Communication check Inverter provides wrong status? Y Physical connection Change of set points Possible if applicable Inverter doesn t follow changes? Y Interfaces Laboratory test 10

11 Array check procedure Low PR Check G POA sensor Check T BOM sensor Low I SC? Low V OC? UNIFORM SOILING BYPASSED CELLS OR MODULES UNIFORM SHADING PID MODULE DEGRADATION Glass corrosion Deg. Of AR coating Discoloration of encapsulant Low FF? Low R SH? High R S? CELL DEGRADATION Cell crack Contact corrosion Weaker solder bonds Broken/interconnects Steps in curve SHADING MISMATCH SOILING MISMATCH CRACKED CELLS BURN MARKS 11

12 Tool for inverter/system analysis Comparison of conversion efficiency Actual vs expected power Inverter efficiency at different power and voltages 12

13 Tool for strings analysis Main features Simulate cabling effects and degradation effects Estimates reference curve where not available from datasheet values Estimates statistical variation of parameter in strings and consequent mismatch Specify degradation modes affecting the string Optionally use of dark I-V measurement to have further information Reference Datasheet Tolerance/mismatch Degradation Cables voltage drop Measured I-V curves Measured I-V curve Correction to STC Vs. 13

14 Interface for string analysis Datasheet values Cables Degradation One diode model parameters Reference vs calculated 14

15 Light and dark I-V curve comparison From the analysis of the deviations we can easily estimate the degradation modes causing under performance Deg. modes FF FF low light I SC V OC ΔR S OPTICAL?? - -? ELECTRICAL CELL PID Deg. modes V D_MAX V P J 0 OPTICAL ELECTRICAL CELL PID

16 What s next? Need for improvement in simulation of degradation >8 years Standardization of on site measurement approaches Improvement on modelling of temperature dynamics Integration of fault detection algorithms into monitoring devices 16

17 Thank you for your kind attention 17