Key Research Areas

Condition monitoring and lifetime prediction of IGBTs for photovoltaic ­inverters

Insulated gate bipolar transistors (IGBTs) are key to the state-of-art inverters used in photovoltaic equipment. Their main function is converting the variable direct current (DC) produced by solar panels into alternating current (AC). Thermomechanical stress induced by cyclic loading is a main cause of semiconductor degradation. IGBT lifetime is primarily dependent on the frequency and amplitude of this cyclic loading.

Against this background, the main goal of CoMoLeFo, a joint project between industry and the Fraunhofer IZM, was to develop a reliable means of assessing system condition and an intelligent technique for predicting the remaining lifetime of power electronics. Condition monitoring and the lifetime prediction that this makes possible can warn of impending age-related failure. This increases the reliability of the entire photovoltaic system and reduces the need for maintenance routines.

CoMoLeFo takes two mutually complementary approaches: IGBT chip temperature is determined by indirectly measuring relevant electrical parameters during operation. To assess the associated stress on the system, the results are evaluated using a mathematical lifetime model. At the same time, diverse parameters and how they change due to aging are monitored in real time. Using these techniques, CoMoLeFo developed software specifically for predicting IGBT remaining lifetime, which is transmitted to customers and service providers by remote access.

Availability, efficiency and reliability are key strategic concerns in the provision and ­operation of power plants. Increasing power plant efficiency and reliability improves competitiveness. For example, planning servicing is easier and downtimes decrease. 

Beyond the primary goals of the CoMoLeFo project, power electronic systems equipped with condition monitoring systems can be applied in a wide range of other areas.

The project was carried out in cooperation with imc Meßsysteme GmbH, First Sensor AG, General Electric Company and the TU Berlin. It was co-sponsored by the TSB Technologiestiftung Berlin (Eng.: TSB Technology Foundation Berlin) using funding from the Land Berlin’s Zukunftsfond (Eng.: Funding for the Future) program and by the EU European Fund for Regional Development (EFRE) program.