�Lifetime Analysis of�Photovoltaic Inverter Based on�Geographical Site of Installation

Abhishek A. Chanekar, Abhinav Arya, Nachiketa Deshmukh, Sandeep Anand

IEEE International Conference on

Power Electronics Drives and Energy Systems

16-19 December 2020 Jaipur, Rajasthan, India

Malaviya National Institute of Technology, Jaipur

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IEEE PEDES 2020

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Presentation Outline

• Reliability of Solar Inverters

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• Failure of power semiconductor devices (PSDs)

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• Literature Review

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• Lifetime Estimation of PSDs

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• Reliability Analysis

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• Conclusions

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Reliability of Solar Inverters

• Survey in Florida: 176 inverters tied to 103 grid PV systems [1]

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• Most of the failures were because of inverters

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• Maintenance / replacement of inverter would highly increase the expenses [2]

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• Reliability study of inverters: Power semiconductor devices (PSDs) as one of the vulnerable components [3]

Fig. 1: Cash flow over a lifetime of solar PV system

1. G. Petrone, G. Spagnuolo, R. Teodorescu, M. Veerachary and M. Vitelli, "Reliability Issues in Photovoltaic Power Processing Systems," in IEEE Transactions on Industrial Electronics, vol. 55, no. 7, pp. 2569-2580, July 2008
2. “A review of PV inverter technology cost and performance projections,” Navigant Consulting, Inc., Burlington, MA, NREL Subcontract Rep. NREL/SR-620-38771, Jan. 2006.
3. T. J. Formica, H. A. Khan and M. G. Pecht, "The Effect of Inverter Failures on the Return on Investment of Solar Photovoltaic Systems," in IEEE Access, vol. 5, pp. 21336-21343, 2017.

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Failure of PSDs: Temperature Cycling

• Temperature varies due to change in ambient condition and load variation
• Thermomechanical stresses between two layers (different CTE) in the device package
• Degradation of device: Bond wire fatigue and Solder fatigue

N. Baker et al., “Improved reliability of power modules: A review of online junction temperature measurement methods,” IEEE Ind. Electron. Mag., vol. 8, no. 3, pp. 17-27, 2014.

Fig. 3: Junction temperature variation over a day

Fig. 2: IGBT module structure

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Literature Review

• Lifetime estimation methods
• Military handbook – simpler but not accurate, no wear out mechanisms
• PoF based models – physical phenomenon, information not available and complex
• Empirical models – simpler, statistical analysis of failure data

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• Yearly mission profile based lifetime analysis of single phase PV inverter topologies

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• Location based lifetime analysis is missing

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Lifetime Estimation of PSDs

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

• Solar energy data is obtained in terms of irradiance(G) and ambient temperature(T_amb)

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• The solar inverter is operated at MPP and I_mpp and V_mpp are calculated

• Losses occurring in the PSDs
• Conduction losses
• Switching losses
• Reverse recovery losses

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

• Lifetime Empirical Models: Scheuermann Lifetime Model

• Miner’s Rule:

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Reliability Analysis

• IGBT based single phase grid connected PV inverter (5kW)
• 4 Transformerless PV inverter topologies considered: Full Bridge, H5, H6, HERIC
• These topologies would behave differently in different locations
• 6 different locations are considered

Fig. 6: Different geographical locations with their coordinates

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Lifetime comparison of PSDs

Fig. 7: Location based relative lifetime for IGBT and Diode in FB inverter

• Lifetime of PSDs are normalized to lifetime of diode located at Kenya

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• Diode having minimum lifetime irrespective of the location

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• Thermal stress occurring at the diode is greater than the IGBTs

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• Device packaging:
• Chip size of diode is smaller
• Heat sink provided is same

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• Poor heat dissipation resulting to increased degradation of the diode

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Effect of Location on Lifetime

Fig. 8: Location based relative lifetime for different inverter topologies

• Lifetime of inverter are normalized to lifetime of FB inverter located at Kenya

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• Kenya and Amazon face highest damage followed by Kolkata

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• High thermal stress on PSDs at these locations which are nearer to equator

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• Higher temperature swing and higher mean temperature

Table 1: Average mean temperature over the year

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Effect of Location on Lifetime

Table 2: ΔTj variation

Fig. 9: Thermal stress cycles at New York

Fig. 10: Thermal stress cycles at Kenya

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Lifetime Analysis of Photovoltaic Inverter Based on Geographical Site of Installation

Conclusions

• The lifetime of solar inverters in the hotter and near the equator regions is reduced due to increased thermal stresses

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• The reliability of anti-parallel diodes is less as compared to the IGBTs

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• The reliability of FB inverter topology is poorest

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• The lifetime of H6 and HERIC inverter topologies are nearly the same

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Thank You

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