Motor condition in braking energy recovery

1.300 to 350s interval

When the engine needs to be accelerated at low speed, the engine is also used. During this process, the generator is not working, and all the recovered energy of the motor is converted to the battery. It should be noted that the recovery power at this time is very low.

2.450 to 600s interval

At high speed, it can be found that as long as the speed changes slightly, the motor recovery power will be very large at this time, but the battery is not used as the main unit for absorbing energy. At this time, the generator's power is changed from power generation to power consumption, dragging the engine. The output power drops.

The above picture, there may be too much data, not too clear (mainly the deceleration process is not very obvious), from the power point of view, the following picture may be more clear, the results are from Model Year 2010 (Gen 3) Extracted from the Toyota Prius Level-1 Testing Report.

Under three different operating conditions, the charging power of the battery is still relatively high. Compared with the previous conclusions, the speed is reduced under high-speed conditions, and the charging power of the battery is not high, which should be the same as before.

Next consider the reverse voltage, which is the voltage of the motor at different speeds.

Therefore, Boost becomes a buck at this time, and the voltage must be lowered to supply voltage. It should be noted that when the battery is low, the battery will also take part of the energy from the generator for charging. The whole charging process is not limited to deceleration.

So the voltage across the bus is always fluctuating

The entire bus voltage is always maintained near 500V for a certain period of time at high speed:

The basics given here are relatively stable voltages, so the filter smoothing capacitor of the entire inverter is very important. If this is not selected, it will have a great impact. In the research direction of EERE, we are always trying to reduce the design requirements and cost of capacitors.