Industrial Power Electronics

Electrical energy is usually transmitted via the central power grid through alternating current (AC) over high-voltage overhead lines. The growing demand for transport capacity for electrical energy over long distances worldwide poses new challenges for industrial power electronics. In addition, renewable energy sources are increasingly being integrated into the power grid, often delivering electrical energy in direct current (DC). Conventional high-voltage overhead lines can therefore only meet the new requirements to a limited extent.

High-voltage direct current (HVDC) transmission is used to support the AC grid. HVDC has significantly reduced losses in long-distance transmission and is therefore more economical than AC transmission in this area of application. The focus at Fraunhofer IISB is on the standardization of components in modular multilevel converters (MMC). These semiconductor-based MMC stations are the most important components at the end points of high-voltage DC transmission. Here, conventional AC transmission incurs transfer losses, which are avoided by MMC solutions. This is made possible by using cascaded semiconductors in the highest current power ranges so that DC current can be generated and regulated flexibly.

With our industry partners, we develop all components of the MMC submodules, including driver switches, safety concepts, key components, and valve-tower design for the MMC stations. In addition, individual failure protection mechanisms are evaluated, tested and assessed.

Cooperating with us, you can expect:

• High availability and reliability at component and system level
• State-of-the-art functional approaches, especially with regard to operational safety
• Many years of experience gained through projects with several international cooperation partners

An optimized system design includes mechanical, electrical and thermal considerations. This is essential to meet the high and often conflicting requirements for reliability, availability, efficiency, power density and system costs. Prototypes are mandatory for qualified engineering evaluation of efficiency in the course of the design process. Our know-how includes near-series designs based on available industrial components. Furthermore, proof-of-concept studies with experimental assemblies and assembly technologies, such as the experimental testing of explosion-proof housing variants, are carried out. Cooperating with the technology experts at Fraunhofer IISB ensures prototyping services from bare-die level.

The operation of power semiconductors requires detailed knowledge of the power circuit, especially when modern high-power semiconductors are switched in parallel. High-dynamic signals have to be measured and evaluated as well as the high voltage. We offer the design and setup of control and monitoring electronics, which are carefully matched to the intended function for the control of high power key components. Based on health monitoring, we develop safety and protection elements for high-voltage networks as well as strategies for handling special load cases, flashovers and redundancies in case of failures.

We conduct design reviews in all phases of development. This includes an overall view as well as the analysis of individual subcomponents. The analysis of field failures and the review of possible failure scenarios is based on decades of experience in the design of power electronics systems at Fraunhofer IISB. For this purpose, we perform on-site measurements in your target applications. As part of the system context analysis, we also consider associated peripherals and application-specific characteristics.

Characterization measurements are relevant in all sub-areas of industrial power electronics to secure proper application in the field. For the operational optimization of industrial customers, the following steps have proven to be particularly effective:

• Analysis of fault scenarios with high-speed camera system and current sensors up to >1 MA.
• Thermal characterization using lock-in thermography, thermostats and climate chambers from -60°C to 300°C
• Lifetime and reliability tests based on active and passive thermal cycling, HALT, electrical stress and vibration
• Partial discharge measurements according to IEC 60270
• Static and dynamic characterization of power semiconductors on semi-automatic test benches for fine-mesh and reproducible characterization of switching behavior over the entire operating range (up to 6500 V and >10 kA)