Bi-Directional DC/DC Converter Reduces Costs

A consortium led by Prodrive has developed an approach to the configuration of DC/DC converters that will reduce the cost, weight and package space associated with electric vehicle battery packs. The system is said to address the spiralling costs of energy storage by increasing the voltage available at the traction motors.

To improve efficiency, electric motors require ever wider speed ranges; as speed is proportional to voltage, electric vehicles and hybrids are progressing from 300V to 600V systems. This creates a challenge because battery chemistry dictates the voltage per cell, so doubling the voltage with the same battery chemistry means doubling the number of cells, incurring cost, weight, and packaging penalties.

More cells, or a switch to an alternative chemistry, may also exacerbate challenges such as thermal management, availability, environmental protection and end-of-life recycling. To address this challenge, the consortium (which also includes the University of Manchester, HILTech Developments, Sloan Electronics , International Transformers and Newcastle University) has developed a bi-directional DC/DC converter that gives a 600V output from a 380V source and maintains its output even when the source voltage drops to as little as 200V.

The key is a new topology that delivers up to 97 per cent efficiency and is also low cost and compact. The power-handling capability is scalable, with development units rated at 50kW for full hybrid applications. The voltage of batteries (and fuel cells and supercapacitors) can fluctuate with changing load, but the Prodrive converter always presents the full voltage required by the motor. Vehicle architecture benefits from a reduced battery pack envelope and weight, and there is an overall cost saving.

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