Power electronics

Power electronics is a very important and integral part of the powertrain unit of every electric vehicle. The power electronics of an electric drive system control the transfer of energy between the main components of electric vehicles, such as the battery, the electric motor, and the charger. The efficiency of a given electric drive is significantly influenced by the architecture of the power electronics.

Power electronics are the essential control unit of any electrified powertrain. They are therefore a crucial component not only in fully electric vehicles like BEVs but also in hybrid vehicles such as PHEVs and HEVs. Thanks to power electronics, electric cars can use the energy from the battery efficiently or, conversely, store kinetic energy stored during braking using regenerative braking. Power electronics also manage the battery charging process. Another important function is converting DC voltage to various voltage levels (12V/48V/400V/800V). The proper and efficient operation of power electronics in these functions depends primarily on advanced semiconductor circuits. These circuits must ensure efficient energy conversion according to current demands, minimize losses, and withstand high temperatures and challenging operating conditions.

A car that uses an electric or electric-hybrid drive system must be able to run on both DC and AC power. The traction battery provides energy in DC, whereas electric motors require three-phase AC for their operation. The power electronics module performs this conversion, adapting the energy type and optimizing its flow.

For fast chargers that provide direct DC power, the vehicle’s power electronics monitor and manage the energy flow to ensure safe and efficient battery charging, protecting it from overvoltage or overheating, and optimizing charging speed. This process contributes to a safe, reliable, and quick energy replenishment for the electric vehicle.


Cross-section of Power Electronics

The power electronics module has a compact design and is often directly attached to the electric motor. The entire module weighs approximately eight kilograms. It includes its cooling system, as it is exposed to significant thermal stress.

Power Electronics


How Power Electronics Work in an EV:

The power electronics module comprises several components, each fulfilling a specific function. When the vehicle is charged from a home power outlet (e.g., 220V), the rectifier [1] converts AC to DC, which is then stored in the high-voltage battery.

Another component, the DC converter [2], reduces the high voltage from the traction battery (e.g., 400V or 800V) to the low-voltage level of the onboard system (12V). In EVs, as in conventional vehicles, the onboard network operates at 12V, making direct connection of standard electronics to the traction battery impossible.

The inverter [4] regulates the speed and torque of the electric motor, modulating its performance characteristics. It converts DC from the battery to three-phase AC required by the electric motor.

Renault Zoe Power Unit and Power Electronics Cross-Section


Did You Know:

Number of Power Electronics Units

If an EV has multiple electric motors, it is typically equipped with a corresponding number of power electronics units, where each unit is responsible for managing one specific motor.

Dividing power management across multiple units offers several advantages. Each motor and its electronics can be optimized for their specific tasks. For example, in all-wheel-drive EVs, the front and rear motors may have different characteristics, such as power, speed, or the ability to handle specific driving modes like acceleration, slippery surfaces, or off-road driving.


Power Electronics Impact on Charging Time

Charging speed can be affected by the power electronics, as their maximum performance depends on the design and capacity of individual components, such as semiconductor converters or cooling systems. If power electronics are designed for lower performance, they may limit charging speed, even if the battery can accept higher power and the charging station can deliver it.

Additionally, power electronics regulate the entire charging process to protect the system from overheating, overloading, or other damage. For example, at high temperatures or when a higher charge level is reached, they may reduce charging speed to protect the battery and ensure safety. To enable fast and efficient charging, both the vehicle and charging infrastructure require adequately powerful electronics.