10 AUTOMOTIVE POWER www.vicorpower.com Issue 1 2024 Power Electronics Europe www.power-mag.com BEV advancements are driving sales, but vehicle safety and reliability will ensure long-term viability Innovative power architectures using power modules provide power redundancy and improve overall safety and system performance By Patrick Kowalyk, Automotive FAE, Vicor Sales of electric vehicles continue to grow globally. March 2023 saw combined (BEV and PHEV) sales of over 322,000 plug-in electric vehicles registered across Europe, a 29% year-on-year increase. Furthermore, battery electric vehicles show a 44% year-on-year increase and account for a 16% share of all cars sold in Europe.1 These figures are good news for all vehicle manufacturers after the dismal car sales during the 2020-2021 COVID-19 period. The rebound in overall sales and the significant rise in EV sales bodes well for the future. Still there remains consumer reticence around charging infrastructure and battery range. In response, manufacturers already have secondgeneration EV models in production addressing consumer concerns. Trends shaping the second generation of electric vehicles There are several trends worth noting. 1. Improving charging time and reducing vehicle weight. Weight directly influences an EV’s range. Therefore, anything that reduces vehicle weight increases the payload and its maximum range. 2. Removing the traditional 12V DC primary battery offers significant weight advantages. Today reducing its size or removing it altogether are options. 3. Migrating to a 48V zonal networking architecture reduces the need for bulky, heavy and costly 4 gauge wire harnesses. Similarly, the move to a 48V architecture for secondary equipment (heated seats, seat movers, etc.) also benefits from reducing cable size and weight. 4. Upgrading from 400V to 800V battery voltage is being quickly adopted. This trend enables reduced cable weight and charging time but requires upgrading the charging post infrastructure to support both voltages. Still, there are other important safety and reliability enhancements needed. There is no escaping the fact that since a BEV derives all its power from a single source— the high-voltage traction battery— any interruption to it is more than inconvenient, it can pose serious safety hazards. So while creature comforts may be captivating consumers and stimulating new sales today, long term viability of the EV platform is dependent on sound safety protocols being designed into the vehicle. In an all-electric automobile power redundancy is essential. Designing-in power redundancy is essential to safety and reliability The addition of a redundant source of energy in an EV ensures safety and reliability for its driver, passengers and other road users. Redundant power is required for three load types: Steering, braking and safety sensor systems Always-on vehicle network (CAN bus, Ethernet, etc.) communication Non-essential loads that can be turned off during critical power situations For example, EV power architects could achieve an 800V traction battery source by connecting two 400V battery packs in series, with each battery configuration having a separate DC-DC (400V to 800V) converter. This configuration (Figure 1) is called a Dual-400V series-stacked system. Some manufacturers are presently using the Dual-400V series-stacked system for several reasons. The primary reason is that charging with a 400V charger is easier because many installed public chargers are not 800V compatible. Today, as new chargers are installed, they can support both 400V and 800V batteries. The second reason is that if a manufacturer has already designed and qualified a 400V battery pack, it is faster and easier to add two packs in series. Another approach is the Dual 800V parallel battery configuration (Figure 2) that involves using two 800V batteries in parallel. Again, two separate DC-DC converters provide redundancy. There are trade-offs with both configurations. When using a Dual-400V series-stacked system these are the drawbacks to consider: The 400V DC-DC converters need more clearance to chassis ground as the topmost DC-DC converter is at 800V. The center tap between the two 400V Figure 1 — Dual-400V series-stacked system Connecting two 400V battery packs in series with separate DC-DC converters in a stacked architecture allows lower-voltage operation and splitting the load to two or more strings (Source: Vicor)
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