Week 4 Session 5
Applications of Power converters in an Electric vehicle
Power converters are widely used in EV applications. Some of them are given below
- AC to DC converter(Rectifiers) - They are used in onboard charger. Here for charging the battery using external supply, Since battery accept only DC, using a AC to DC converter, external AC supply is converter into DC (for example 230V AC to 230V DC). They are used mainly used in Plug-in Hybrid electric vehicle(PHEV) and Plug-in electric vehicle(PEV)
- DC to DC converter (choppers)-This converters can either step-up or step-down of DC voltage. As we know after use of rectifiers in on board charger, that rectified DC must again step up or step down based on level of charging(example Level 1, Level- 2 charging). For DC fast charging we can directly use a step up DC-DC converter. There is an auxilliary battery in EV used for powering the head light, Side mirror and other infotainment system. So here come the use of DC DC converter, it step down the voltage of auxilliary battery and fed it into the systems.This DC DC converter act a inferface element between battery and DC motor. Which control the speed of motor by varying the voltage applied to it from battery.
- DC to AC Converter( Inverter) -
The power output from battery pack (DC) is converted using inverter to be used in electric motor(ACmotor).For induction motor drive Inverter are used.
In the electric vehicle (EV) powertrain, all the electric input sources are connected to a HV–DC bus by an individual DC–DC converter, and the output three-phase electric motor (EM), i.e., the main load of the EV, is powered from this HV–DC bus through a three-phase inverter which drives the EM. Here, the voltage level of this HV–DC bus of the EV is around 400–750 V. Moreover, moving the EV via an EM from electric batteries, a DC–DC voltage is required because the batteries’ output voltage is much lower than the required voltage of EM. A traction inverter is needed to drive the EM by converting the DC batteries into variable-frequency AC.