Calculation Steady State Speed of Electric Vechicle

AIM:

1. To study the power converters used in vehicle.

2. To calculate the steady state speed of Electric Vehicle.

3. To Study the Induction motor and brushless motor.

KEYWORDS: Power converter, Inverter, Duty cycle, Electric vehicle, Induction motor, Brushless motor.

SOFTWARE: Matlab

OBJECTIVE:

1. Study about power converters used in EV and HEV.

2. Calculating the steady state speed of Electric Vehicle for 70% duty cycle by using Vehicle characteristics and Motor characteristics.

3. Conclude Induction motor and brushless motor by author's perspective.

INTRODUCTION:

Study 1:-

Figure-1: Block diagram of Electric vehicle powertrain

The above figure powertrain block consists of DC-DC converter and inverter (DC-AC ). The DC-DC converter is a fixed DC input voltage into variable DC voltage or vice versa. The DC output voltage is controlled by varying of duty cycle.

This electrical device actually changes the voltage (either AC or DC) of an electrical power source. There are two types of voltage converters: step up converters (boost converter) and step down converters (buck converter). The most common use of a converter is to a take relatively low voltage source and step-it-up to high voltage for heavy-duty work in a high power consumption load, but they can also be used in reverse to reduce voltage for a light load source.

In EV, the main source of electric energy from battery to drive the motor. To circulate these energy continously to auxilaries, boost converter are used to increase the voltage with low current. The main features of Boost converter are,

• Continuous input current, eliminates input filter.
• Pulsed output current increases output voltage ripple.
• Output voltage is always greater than input voltage.

Figure-2: Block diagram of Hybrid Electric vehicle powertrain

The above figure powertrain block consists of DC-DC converter, AC-DC converter (Rectifier) and inverter (DC-AC ). The DC-DC converter is a fixed DC input voltage into variable DC voltage or vice versa. In HEV, the main source of electric energy from engine generator to drive the motor, with assistance from battery. To circulate these energy continously to auxilaries, buck converter and boost converter are used to vary the voltage wrt current.

Boost converter

• Continuous input current, eliminates input filter.
• Pulsed output current increases output voltage ripple.
• Output voltage is always greater than input voltage.

Buck converter

• Pulsed input current, requires input filter.
• Continuous output current results in lower output voltage ripple.
• Output voltage is always less than input voltage.

A Rectifier is an electrical device that converts alternating current, which periodically reverses direction, to direct current, which flows in only one direction. The process is known as rectification, since it "straightens" the direction of current. A rectifier converts the whole of the input waveform of alternate current to one of constant polarity or only positive polarity at its output which forms continous current or direct current. This DC obtained from generator which helps to charge the battery.

#Calculating Steady state speed of Electric Vehicle.

clear all;clc
close all

%Motor constant and flux per pole
Km_Phi = 0.7;
%Armature Resistance
Ra = 0.5;
%Supply Voltage
Es = 72;
%Duty Cycle in Percentage
d = 0.7;
%Calculating Supply voltage for 70% of duty cycle 
Es1 = 50.4;
%Angular Velocity in rad/s
w = [0:0.01:50];
%Calculated Vehicle Characteristics
Tv = 24.7+(0.0051.*w.^2);
%Calculated Motor Characteristics
Tm = ((Km_Phi * Es1) / Ra) - (((Km_Phi)^2 / Ra ) * w);
%Tm = 70.56 - (0.98*w);
%Plotting Velocity against Vehicle Characteristics
plot(w,Tv);
xlabel('w (rad/s)')
ylabel('T (N-m)')
title('Steady State Speed of EV')
axis([0 50 0 80])
hold on
%Plotting Velocity against Motor Characteristics
plot(w,Tm);

CONCLUSION: