Week 4 Session 5

Solution:

Application of Power Converters in an Electric Vehicle:

Power converter is an electrical circuit that converts the electrical input signal from one form and level to other using high frequeny switching action. Types of power converters used in Electric vehicles are:

1. AC - DC Converter (Rectifier)
2. DC - DC Converter (Chopper)
3. DC - AC Converter (Inverter)

AC - DC Converter (Rectifier)

• AC - DC converter converts unregulated AC input to DC output.
• These converters are also called rectifiers.
• In EVs/HEVs rectifiers are mainly used in onboard chargers.
• The AC supply from the charging pont is converted into DC power to charge the battery, where the DC power is stored in EVs and HEVs.

DC - DC Converter (Chopper)

• DC - Dc converter converts unregulated DC input to a regulated DC output, it converts DC voltage from one voltage level to another. It can be step up or step down of voltage.
• This type of converter is also known as chopper.
• Types of DC - DC converters
  • Non Isolated Converters : Buck, Boost, Buck Boost Converters
  • Isolated Converters : Flyback, Forward, Half Bridge, Full Bridge
  • Resonant Converters : It is used for high power conversion
• The electric components inside the vehicle vary in their voltage requirements, with most running on much lower voltage. This includes radio, dashboard readouts, air conditioning, and in-built computers and displays, horns, etc.
• The voltage level required for these components are much less in the range of 10 - 12 V, hence DC-DC converter converts the DC voltage from the main battery (High voltage) to low voltage which will be stored in axuillary battery and is used to power these components.

DC - AC Converter (Inverter)

• DC-AC converter change a dc input voltage to a symmetric ac output voltage of desired magnitude and frequency.
• This type of converter is also known as inverter.
• In EVs/HEVs inverters are mainly used in motor drive where AC motors (Induction motors) are used as traction motor.
• The inverter circuit is used for speed control of motor, it can change the speed of the motor by adjusting the frequency of the alternating current.
• When the vehicle has to be accelerated, the accelerator pedal sends a signal to the controller which adjusts the vehicle's speed by changing the frequency of the AC power from the inverter to the motor.