Week-6 Challenge: EV Drivetrain

1. Which types of power converter circuits are employed in electric and hybrid electric vehicle?

Power converter:

Power converter is a device used to convert electric energy to other form of energy. It is also used in control of the energy supply.

It is a electro mechanical device which can change AC supply inro DC and vice versa

There are three types of power converter circuits:

• AC to DC
• DC to AC
• DC to DC

AC to DC - rectifier

Electrical power supply became as a basic need in our day-to-day life, the power we are availing is 230V 50Hz AC supply. But, by using power electronics converter circuits this power can be converted into the required form and range. These converters are power electronics circuits which are further classified as step-down & step-up converters, voltage stabilizer circuit, AC to DC, DC to DC, DC to AC converter circuits and so on. Most of the microcontrollers which we frequently use in designing electronics projects require a 5V DC supply, this 5V DC can be obtained from available 230V AC supply by using AC to DC converter in the power supply circuit.

DC to AC - inverter

DC to AC converters is mainly designed for changing a DC power supply to an AC power supply. Here, DC power supply is comparatively stable as well as positive voltage source whereas AC oscillates approximately a 0V base stage, typically in a sinusoidal or square or mode.

DC to AC Converter

The common inverter technology used in electronics is to convert a voltage source from a battery into an AC signal. Generally, they operate with 12 volts and commonly used in applications like automotive, lead-acid technology, photovoltaic cells, etc.

A transformer coil system & a switch is the simple circuit used for an inverter. A typical transformer can be connected toward the DC signal’s input through a switch to oscillate back quickly. Due to the current flow in bi-directional in the primary coil of the transformer, an alternating current signal is an output throughout the secondary coils.

2) An Electric Vehicle's powertrain with 72V battery pack in shown in the diagram below. The duty ratio for acceleration operation is 'd1' and for the braking operation the duty ratio is 'd2'.

Given,

Motor and controller parameters:

Rated Armature voltage= 72V

Rated armature current= 400A

Armature Resistance Ra= 0.50hm

kg= 0.7 Volt Second

Chopper Switching frequency= 400Hz

The vehicle speed-torque characteristics are given by the equation= Tv24.7+(0.0051)() ^2

We need to find thee steady state speed of EV at 70% of duty cycle.

We know, the torque equation,

T= ((Vo*kg)- ((kp) ^2*w))/R-

where,

T= torque

V= Armature voltage

R= Armature Resistance

w= Angular speed

From the question, we have to calculate the motor speed at 70% of duty cycle. So, the output voltage , here, Vo= D *Vin

here, Duty cycle D= 0.7 (70%)

therefore, Vo=(0.7)*(72)

(since V=72V given)

= 50.4V

T=(50.4*0.7)-((0.7)^2)*w)/0.5

T=70.56-0.98w

70.56-0.98w= 24.7+ (0.0051* (w)^2)

0.0051(w^2) +0.98 (w)-45.86=0

W=(-0.98+sqrt(0.98^2-(4*0.0051*-45.86)))/(2*0.0051) and

(-0.98-sqrt(0.98^2-(4*0.0051*-45.86)))/(2*0.0051)

W=38.915 rad/sec

3. Develop a mathematical model of a DC Motor for the below equation using Simulink.