Inverter

Photovoltaic inverters convert the DC voltage of solar modules into grid-compatible AC voltage and are increasingly taking on additional tasks such as grid support and energy management. Such inverters are used everywhere, from private household appliances to power plants. Their importance has increased once again as a result of the energy transition, as they are essential not only for photovoltaic (PV) systems, but also for battery storage systems such as those used in electromobility or energy grid management. However, they have to cope with considerable loads for these applications: they are exposed to the effects of high electrical voltages, dirt, wind and weather in almost uninterrupted operation.

Despite these loads, high-quality inverters typically achieve a service life of up to 25 years. Manufacturers rely on manufacturing processes and materials that can be expected to provide the necessary robustness, usually based on experience. However, there is usually no in-depth understanding of ageing processes, failure mechanisms or defect risks for the individual components within an inverter. This also means that the opportunity to leverage efficiency potential is lost, which entails corresponding additional costs.

Power capacitors, in particular MKP technology (metallized polypropylene film capacitors), play an important role in inverters. The most important ageing mechanisms of these capacitors are known and are influenced by voltage, temperature and humidity. The interactions between these factors play a particularly important role in terms of reliability and service life. At the Fraunhofer IMWS, they can be evaluated and integrated into a quantitative ageing model. With their expertise in materials science and their extensive experience in the development of test methods, the Fraunhofer experts can develop suitable models and parameters that allow reliable predictions to be made for the service life of electromechanical switches under changing environmental influences, even for contacts that are rarely or never switched.

By using empirical data and representative load collectives, realistic reliability and service life forecasts can be created. Efficient statistical planning of the tests allows maximum information content to be generated with minimum effort.

Why are reliability predictions crucial?

Reliability predictions provide a scientifically sound basis for assessing the service life and performance of PV and battery inverters. Precise forecasts allow potential weak points to be identified at an early stage and preventive measures to be taken to minimize failures and reduce operating costs.

The advantages of reliable inverters

• Minimization of downtimes: A reliable inverter reduces unforeseen downtime and ensures continuous energy production.
• Cost efficiency: By reducing repair and replacement costs, reliable inverters help to lower the total cost of ownership.
• Longer service life: High-quality inverters, whose reliability is regularly predicted and monitored, have a longer service life and thus maximize the return on investment.