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HiPE-LAB: Testing Power Electronics to their Limits
17 Sep 2025
The High-Power Electronics Laboratory (HiPE-LAB) at the University of Bremen tests power electronics of up to 10.8 MVA under combined climatic loads of –40 to +120 °C and 10 to 95% relative humidity, as well as electrical loads. Realistic reliability analysis is enabled by multimodal, automated long-term tests including data monitoring.
The HiPE-LAB is operated by the Institute for Electrical Drives, Power Electronics and Devices (IALB) at the University of Bremen, in collaboration with the Fraunhofer Institute for Wind Energy Systems IWES. Currently, a long-term reliability test involving a device under test (DUT) from SMA Solar Technology in Kassel, Germany, is underway.
»Our HiPE-LAB test laboratory enables multimodal lifetime tests of power electronics up to 10.8 MVA power-in-the-loop. This allows us to better evaluate the effects of environmental conditions on power converters, for example«, explains Dr.-Ing. Wilfried Holzke, Scientific Head of the HiPE-LAB. He adds that it is precisely these multimodal tests — the combination of climatic tests with electrical loads — and the institute’s research focus on the reliability of power semiconductors under the direction of Prof. Dr.-Ing. Nando Kaminski at the IALB, that constitute the laboratory’s unique selling point. »At the heart of the laboratory is a 170 m³ climate chamber with a temperature range of -40 to +120 °C and relative humidity between 10 and 95% within a temperature range of +10 to +95 °C. This allows almost all climate zones to be simulated realistically«, Holzke continues. At the same time, dynamic, reproducible electrical load profiles can be created to generate combined environmental and operational conditions. In advance, these load profiles are agreed with the customer and then implemented and finally executed fully automatically. The DUT is integrated into the test bench control system, for which a wide range of data interfaces and bus protocols are available.
Images: HiPE-Lab
In addition to confirming that the DUT can be operated successfully under the specified conditions, extensive measurement equipment is available to gain further insights. »Of course, customer-specific sensors can be integrated«, says Holzke. Data acquisition is an integral part of the automation system. This means that new measurement data can be made available to customers on a daily basis. Ongoing measurement data acquisition is visualised in real time for each customer individually.
Besides connecting the DUT to the electric grid, voltages with different frequencies and amplitudes can be provided via the electrical load system in the HiPE-LAB. Flexible control of the individual load units allows different generator types and grid conditions to be simulated. In the future, it will be possible to even simulate grid faults.
»It’s not just entire systems, such as the power converters mentioned above, that can be tested. We also test individual power stacks and single components, mainly power semiconductors,« says Prof. Kaminski. All assemblies and components related to power electronics are also examined for reliability and interaction. Climate chambers are used for “High Voltage-High Humidity High Temperature Reverse Bias”-Tests (HV-H3TRB) as well. Additional test stands are available for power cycling tests (PCT).
Research areas and typical test scenarios
The test stands described above enable researchers at the HiPE-LAB to examine customers’ systems with regard to the following questions: How does the power converter behave when it is started up after a long period of inactivity, in which it has absorbed moisture? Does condensation occur? How quickly does the system heat up due to its own losses? Which components or areas of the converter cabinet are particularly critical? The focus of the research at the HiPE-LAB is answering these and other questions, based on field experience and individual tests, already during the development phase of a power electronic system.
According to Prof. Kaminski, both semiconductor and power converter manufacturers use the IALB and HiPE-LAB facilities. While semiconductor manufacturers have their own test facilities for their products, they still use HiPE-LAB »for testing beyond the standard conditions, long-term investigation beyond the usual 1000 h or combined testing beyond a single stress«, Kaminski explains. There are also customers who simply do not have their own testing infrastructure in this performance class, or whose existing capacities are fully utilised. The spectrum ranges from short tests to continuous stress applied over several months. For instance, a customer was involved in a project carrying out so-called »damp-heat tests«, in which a power converter was stored for several days at 50 °C and 95% relative humidity (RH). The aim of this investigation was to identify differences based on measurements before and after the test that would indicate any necessary improvements. Holzke continues, »In another test, we successfully reproduced a fault, which happened in the field, by applying the same harsh conditions to a DUT. In parallel, an improved version of the product was tested at the same conditions and helped the customer to verify that the improvements were successful.«
Holzke reports that »the industry currently uses a temperature range of -40 to +70 °C and tests as part of research projects have already been carried out at temperatures of up to 80 °C«. In addition, many other services are available, including purely electrical stress tests, purely climatic tests (humidity and temperature), system analysis, modelling & simulation, and component characterisation. These are also offered in cooperation with Fraunhofer IWES.
"This laboratory never fails to impress me with its capabilities. We can carry out realistic validations and analyses of efficiency and reliability, as well as accelerated life tests, on individual components and entire power converters of up to 10.8 MVA."
Cooperation and Research partner: Fraunhofer Institute for Wind Energy Systems IWES
Established under the HiPE-WiND project as a joint initiative of IALB and Fraunhofer IWES, the HiPE-LAB has since been integral to the follow-up projects ReCoWind and ReCoWind2, contributing critical research to boost the reliability of wind power converters.
Field evidence underscores the need: analysis spanning more than 20,000 wind-turbine operating years show failure rates of up to 0.5 damage-related incidents per turbine per year, with early-life failures and sensitivity to environmental factors dominating. These failures are not limited to power semiconductor modules but occur across the entire converter system. Dr.-Ing Katharina Fischer, Senior Scientist at Fraunhofer IWES emphasises: »The implication is clear. Enhanced, application-driven test methodologies are essential. Conventional standards, such as IEC 60068 and IEC 60749, approximate environments only in simplified form, while real conditions vary significantly depending on the application (wind, PV, traction, power transmission). Using our comprehensive database of climatic field measurements and operational data from wind turbines across multiple regions and climate zones, we develop tailored test profiles.«
To deepen the understanding of moisture ingress into the system, extended tests have been carried out as part of the above-mentioned research projects. In one campaign to characterise the hygrothermal behaviour of a wind energy converter, forty humidity and temperature sensors, ranging from ambient air measurements down to specially instrumented IGBT modules, recorded the climatic conditions along the entire path during multi-week tests. The recorded data are used to calibrate hygrothermal models that help to assess the moisture uptake of the DUT at the intended deployment site.
»Photovoltaic inverters face similar climatic and operational challenges as converters in wind turbines; consequently, joint research has been ongoing in this field. This is also how the collaboration with industry partner SMA was established «, adds Martin Hippenstiel, Senior Researcher at Fraunhofer IWES and project manager of the current collaboration with SMA.
Industry partner: SMA Solar Technology
SMA Solar Technology and its subsidiaries develop, manufacture and sell systems and solutions for efficiently and sustainably generating, storing and using solar energy. These include solar and battery inverters, monitoring systems for solar power plants and charging solutions for electric vehicles. The company also offers intelligent energy management systems and digital services for the future energy supply. The offering is rounded out by comprehensive services, medium-voltage technology and power supplies for hydrogen production.
Accelerated ageing tests on power electronics are a valuable way of ensuring the reliable and cost-effective provision of renewable energy supplies. Besides conducting such tests on critical components of its inverters, SMA Solar Technology also carries out ageing tests on entire inverter systems, some of which go well beyond the tests required by the established reliability standard IEC 62093. Due to the complexity and effort involved in conducting these tests, SMA Solar Technology relies on extensive internal testing capacities, as well as testing by external service providers. »We are delighted to have found partners in Fraunhofer IWES and HiPE-LAB at the University of Bremen, who can subject a multi-MW-class inverter to long-term reliability testing under challenging climatic conditions«, says Daniel Clemens, Reliability Technical Manager at SMA. »We particularly appreciate the close coordination and flexibility in the test design. This enables even the most complex test scenarios to be carried out efficiently within the dynamic development phase of a new product.«
Customer’s voltage source in the HiPE-LAB. Images: HiPE-Lab.
Summary
HiPE-LAB enables customised tests on power electronic systems during their development phase, as well as for the optimisation of products already in use. Fully automated testing and the collection of measurement data over several weeks or even months allow industrial customers and research partners to continuously evaluate and improve products and testing procedures. st
Technical data of the HiPE-LAB
Climate chamber:
Size: 7.5 m x 5.3 m x 4.3 m (length x width x height)
Temperature range: -40 to +120 °C
Humidity: 10–95% at a temperature of +10 to +95 °C
