Week 4 Session 5
Challenge 5:
Explain the various applications of Power converters in an Electric vehicle. For Example what type of converter will you use for Horn which requires DC and less than 10V. Likewise come up with different applications
The power from battery/ultra-capacitor, fuel cell or ICE is utilized to drive the vehicle and functions of onboard electrical/electronic load. In fuel mode, the voltage from the fuel cell is not sufficient to drive the vehicle. Therefore, it is boosted by the unidirectional boost converter. Various electrical/electronic loads are present on the vehicle, which increase the luxurious features and comfort of the vehicle.
Some electrical loads require high AC voltage, such as air conditioner and power windows, which receive power from a DC-AC converter. Mirror adjustment and drive seat adjustment work on a DC motor feed from a battery or fuel cell through a DC-DC converter. All these electrical loads operate at different voltage ratings. The projector lamp requires 42 V for projecting the light, and the interior lamp requires 12 V for its operation. Electronic loads such as sensors, communication systems and tacho-metre require low voltage for their operation. The need of different rated voltage supplies increases as the electrical/electronic load increases on the vehicle, which is not possible from a single battery supply. The number of DC-DC converters increases with increasing different rated loads, which results in a lower efficiency of a single battery structure vehicular system. Two types of architecture are adopted in the hybrid automobile system. One is a vehicular system that works on ICE or a fuel cell with a single battery (36 V). Another is the ICE, or fuel cell, which works with a double battery (14 V and 42 V).
The typical structure of the dual battery system is shown in Figure. In the dual battery system, dual voltage is generated from a generator in HEV or from the grid in a PEV. The 36 V battery is utilized for mid voltage applications and the 12 V battery for low voltage applications. However, 36 V from the battery is boosted to 42 V for the drive and high voltage applications. The typical electrical system of EVs is shown in Figure. The voltage generated from the generator optimizes to charge the battery with the help of the rectifier and unidirectional DC-DC converter in SHEV and SPHEV, to drive the vehicle in PHEV and FCEV. The voltage from the fuel cell and the battery is boosted by the unidirectional and bidirectional DC-DC converters, respectively. The boosted voltage supplies to high voltage DC applications and is converted into the variable frequency and voltage with the help of a three-phase inverter. Advanced EVs can utilize the wasted energy during deceleration and braking to charge the battery. In regenerative braking mode, the three-phase converter works as a three-phase rectifier. The rectified output is converted to the battery voltage with the help of a bidirectional DC-DC converter.
Figure: Dual battery scheme for EVs.
Figure: General electrical structure of EVs