Power electronics for EV chargers

As electric vehicles become widespread, so must the infrastructure to charge them. One of the main requirements for the widespread use of electric vehicles is an accessible EV charging infrastructure. Governments and industries worldwide are investing in charging infrastructures, with a growing trend toward bidirectional charging.

Charging an electric vehicle, just like “filling up” a traditional vehicle, is a central aim for the acceptance of all-electric long-distance travel. On the road, the charging process must therefore take just a few minutes, which requires a fast charging infrastructure that is as similar as possible to the present-day network of filling stations for fossil fuels. Charging stations with fast charging points are therefore the market segment of the charging infrastructure that comparatively requires the most powerful semiconductor modules.

Due to the limitation of the charging current in present battery technology, fast charging points are primarily for fast intermediate charging (extension of the vehicle’s range) and not for the purpose of fully charging the battery. With the battery technology of today, charging currents of over 150 A are only possible at the expense of battery life. In addition, as a battery fill level (State of Charge, SoC) increases the charging current strength must be reduced. With the present-day battery technology, this limits fast intermediate charging to a range of between 30% and about 80% of the battery capacity. Fast charging therefore must supplement the full charging performed when the electric vehicle makes long stops.

For short charging times of less than 30 minutes, a charging power of 40 kW is required for a battery capacity of about 20 kWh. The ‘on-board’ charging technique with AC/DC converters used for lower wattages and usually fed from the 230 V network is no longer economical on account of the power necessary for fast charging. Above a charging power of about 22 kW, DC fast charging points where the required DC voltage is generated ‘off-board’ from the AC energy supply network are therefore favoured. Modern power semiconductor modules are imperative for such fast charging points.

Power electronics are a key technology for the mobility of the future based on hybrid and all electric powered vehicles. If possible, unsupervised outdoor fast-charging stations must operate reliably and safely for 20 years. Requirements are therefore made of the power semiconductor modules not only in terms of low losses and module topologies that enable the charging points to have small dimensions, but also in terms of a high degree of reliability over a wide temperature range and at the lowest possible cost.

SEMIKRON has many years of experience in the field of power modules for a wide variety of energy converters ranging from just a few kW up to several MW, for example, for solar and wind energy utilization, power quality and in electric vehicles.

In its power modules, SEMIKRON uses mounting and connection technologies with solder, sinter, pressure and spring contacts. When used in charging stations, these technologies meet the requirements of reliability and robustness. Conventional IGBT modules, SKiiP-IPMs, power modules with diodes and thyristors, discrete semiconductors, as well as tested and ready-to-use power assemblies are available. To be able to provide assemblies with high switching frequencies, SEMIKRON manufactures both modules with fast switching chips with silicon and silicon carbide technology as well as modules with 3-level NPC and TNPC topology.

For more information: https://www.semikron-danfoss.com/applications/industry/ev-chargers.html.