Diodes, Shading, and Reverse Bias: Task Group 4

Task Group 4’s initial goal was to identify and address the key factors responsible for premature catastrophic failures of bypass diodes in manufacturing lines, as well as in field. An ongoing activity has been to collect field-failed samples and perform failure analysis to establish the likely cause of failure.

Planned Activities

  1. Assessing the reliability of bypass diodes under long-term application of the following stressors: high-temperature operating life in forward bias; high-temperature operating life in reverse bias; and thermal cycling with current through the bypass diodes
  2. Studying the effect of continuous submergence on junction boxes attached to the modules
  3. Addressing the system level considerations (e.g., blocking diodes in string combiner boxes) that can lead to diode failures
  4. Studying the time evolution of hotspots generated in photovoltaic (PV) modules due to continues partial shading.

Progress Update

Task Group 4 efforts have led to the development of an International Electrotechnical Commission (IEC)  standard on electrostatic discharge susceptibility assessment of bypass diodes (IEC TS 62916:2017). Moreover, IEC 62979:2017 has been developed  to address the vulnerability of bypass diodes against thermal runaway while transitioning from forward to reverse bias. Recently,  the task group’s work has led to revision of bypass diode thermal test which is included in the IEC TS 63126 ED1, published in 2020.

Standards Activities

IEC TS 62916:2017: PV modules – Bypass diode electrostatic discharge susceptibility testing

IEC 62979:2017: PV modules – Photovoltaic modules - Bypass diode - Thermal runaway test

IEC TS 63126:2020: Guidelines for qualifying PV modules, components and materials for operation at high temperatures

Related Resources

Revising the Bypass Diode Test to Incorporate the Effects of Photovoltaic Module Mounting Configuration and Climate of Deployment
Authors: Shiradkar, N. S., Gade, V. S., Schneller, E. J., & Sundaram, K. B.
Conference: 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC)

Predicting service life of bypass diodes in photovoltaic modules
Authors: Shiradkar, N., Gade, V., & Sundaram, K.
Conference: 2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC)

Thermal Resistance Measurement of Bypass Diode / Junction Boxes.
Authors: Shiradkar, N., Gade, V., & Sundaram, K
Workshop: 2015 PV Module Reliability Workshop

Task Leaders

Narendra Shiradkar – National Centre for Photovoltaic Research and Education, IIT Bombay
Xian Dong — Zhongshan University, representing China
Chandler Zhang — Hohai University, representing China