Electric vehicles are offering ever greater operating ranges

The market for electric road vehicles will continue to grow and in the course of this battery-only passenger cars will offer ever-greater operating ranges.

The essential prerequisites for this development are not only high-efficiency motor drives and lightweight, high-capacity vehicle batteries, but also a nationwide charging infrastructure with charging facilities at private and public parking spaces and car parks, such as inner-city or suburban shopping and commercial centres, or at ‘power filling stations’, i.e. charging stations with several fast charging points on major highways such as motorways and trunk roads.

Charging station with multiple fast charging points

Charging station with multiple fast charging points

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 has to supplement the full charging performed when the electric vehicle makes long stops.

Short charging times by means of power electronics

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. 

Many years of experience with power converters

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. 

Power semiconductors are the core element of fast charging points

With modern power semiconductors, power can be used in a network-friendly way and the charging current can be controlled in line with demand. The optimal balance between the charging time and battery-saving charging strategies can be achieved by this means. High switching frequencies are possible with the latest semiconductor chips made of silicon or silicon carbide and special module topologies enable the use of space-saving passive components.
The characteristics of the power modules of today allow all charging points at a location to be supplied from one central mains converter. 

Key components of future electric mobility

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. Outages of large-scale systems at a ‘power filling station’ on the motorway could cause vehicles to be abandoned. Compared to petrol and diesel filling stations, the effects of this would be more dramatic, because the energy reserves in an electric vehicle are smaller and the charging station network is less dense.

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.

SEMIKRON Products for DC Fast Charging Points