Industrial Power Electronics

Electrical power is usually transmitted through alternating current (AC), but the alternative way of using High-Voltage Direct-Current (HV DC) transmission becomes more and more popular. It shows advantages in the use of submarine cables with no reactive power loss compared to AC transmission, that cannot be used at lengths larger than 30 km. Compared with other three-phase electric power lines, it has less transmission losses and is, at distances above 600 km, even more economic. HV DC transmission can also serve as a buffer between power grids during a power outage or as a connection between two asynchronous grids. Since now an HV DC transmission can only connect two points in a grid with a straight connection.

The most important parts in HV DC transmission are the converter stations at the endpoints of those connections. Fraunhofer works together with industrial partners on HV DC components. Different protection concepts against the failure of the components result in these collaborations, but also specific subcomponents like driver circuits for the power modules used in the converter stations. With that we have a steady view on high reliability, since all these parts have operating times larger than 30 years.

R&D Topics

The requirements in power electronics are driven with the renewable energies and the arising of multiple subgrids. Connected to this development new challenges come up throughout all levels in the energy supply. Generation (inverters for photovoltaic modules, wind turbines, etc.) and transportation (HV DC, SVC, FACTS, OLTC) [1] of electrical power are to mention here.

Trends in power electronics are:

a) New functual approaches. Current solutions cannot satisfy the approaches. For example the ability to restart a power grid after a break down - called black-start-ability – or the requirements towards the operational reliability like handling shortage or flashover in a voltage range from several hundred kilovolts to 1.2 megavolts across large distances.

b) New requirements towards availablility and lifecycles. The lifecycle of systems in the infrastructure of energy generation and transportation are up to 40 years with a 24-hour duty-cycle. There are no long time experiences with with the usage of power electronics over such a period of time[2] . Reliability is another important topic because of the vast consequences of a power failure. New solutions in component and system level are demanded that enable an uninterruptable operation during a failure.

c) Compatibility and stability of power grids. With the growing shares of decentralized generators the frequency and phase of the power grid is not controlled by large synchronous generators that keep the grid stable at large load variations. These are new  demands on converters and their control and filter structures. Stationary and mobile energy storages gain in importance to keep the grids stable. For example battery stations or bidirectional charger systems for electrical cars (V2G) and the power electronics involved with them.

Our topics with that

  • Topology (double modules, reverse-blocking cells)
  • Multi-Terminal Grids
  • Operational reliable Single-Power-Storages
  • DC-Breaker
  • Paralleling highest current power semiconductors

  • Design of higher voltage class semiconductors
  • Solutions against flashovers
  • Longterm-failure mechanisms
  • Diagnosis, modeling and monitoring of system condition (health-monitoring)
  • Solutions for avoidance and minimization of damage during a failure

  • Upwards blocking DC-Breaker (failure shutdown)
  • Control of spread conductors and DC grids
  • New filter and converter structures (multi-level converter)
  • Defined overload ability of converter (for grid stability when adding large loads)
  • Large coupled AC/DC grids
  • Hot-plug-ability and black-start-ablility of micro-grid-systems after a black-out

Focus areas:

  • High-power, high-voltage solutions for HVDC links, static VAR compensators, and active filters
  • Active frontends for grid-compatible power electro­nic systems
  • Safety, monitoring, and protection elements for high-voltage grids (e.g., DC breakers, crow-bars, current sensors)
  • System designs for very high lifetime and availability require­ments

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[1] HGÜ: Hochspannungsgleichstromübertragung; SVC Static VAR Compensator; FACTS: Flexible AC Transmission System; OLTC: Onload Tapchangers for Transformers.

[2] Halbleiterbasierte Leis­tungs­elektronik an sich gibt es erst seit rund 40 Jahren!

Products & Services

System Design and Prototype Development

To meet the high and often contradictory require­ments regarding reliability, avail­ability, effi­ciency, power density, and system-costs an integrated system design, in­corporating mecha­nical, electrical, and thermal design aspects, is essential. Prototypes are mandatory for a qualified engi­ne­ering assessment of the performance in an early phase of the design process, too.

We offer a complete proto­typing process chain from 3D construction to assembly of first small batch series. This includes designs close to series production based on available industrial com­ponents as well as proof-of-concept studies involving experimental parts and assembly technologies. In cooperation with our in-house technology experts, we can offer proto­typing services starting at bare-die level.

Development of Gate Drivers and Monitoring Electronics

The control of power semiconductors requires detailed knowledge of the power circuit. Highly dynamic signals must be measured and evaluated. Different kind of current sensors are used, also the measurement of high voltage poses a challenge. The controlling of high power devices must be carefully adapted to the selected component in order to ensure an optimum regarding robustness, losses, and EMI. We provide the development of control and monitoring electronics.

Failure Analyses and Design Reviews

We perform design reviews in all stages of development. This includes a general view, e.g., assessment of potential sources of failure at system, circuit, and pro­duction level. We offer analysis of field rejections and review of possible break­down scenarios based on de­cades of experience in power electronics system design.

Component and System Characterization

We can provide many years of experience in reliable characteri­za­tion measurements for industrial custo­mers. Our test capabilities comprise, among others:

  • Analysis of high-energy failure scenarios (with high-speed camera system and current sensors up to 800 kA)
  • Thermal characterization (Zth, lock-in thermography, thermostats and climate chambers from ‑60°C up to 300°C)
  • Lifetime and reliability tests (active and passive tem­pe­rature cycling, HALT, electrical stress, vibration)
  • Partial discharge measurements (IEC 60270)
  • Static and dynamic characterization of power semi­con­ductors (semi-automatic test benches for fine-meshed and reproducible characterization of the switching be­havior throughout the entire operating range (up to 6500 V and 6 kA))
© Fraunhofer IISB
© Fraunhofer IISB

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