Introduction

The topics covered in this chapter are as follows:

• •  Need for PWM

•  Single Pulse Width Modulation

•  Sinusoidal Pulse Width Modulation

•  Three Phase Sinusoidal Pulse Width Modulation

Need for PWM in Voltage Source Inverters

The electric motors used in EV applications are required to have large speed ranges as shown in Figure 1 . Large speed ranges can be achieved by feeding the motor with voltages of different frequencies and also different voltage magnitudes. One of the most convenient voltage control technique to generate variable frequency and magnitude voltages is Pulse Width Modulation (PWM).

Figure 1: Ideal performance characteristics for a traction motor

The voltage control techniques for single phase inverters are:

• • Single Pulse Width Modulation

• Multiple Pulse Width Modulation

• Sinusoidal Pulse Width Modulation

• Modified Sinusoidal Pulse Width Modulation

• Phase Displacement Control

Some of the important voltage control techniques for three phase inverters are:

• • Sinusoidal PWM

• Space vector modulation

In this lecture, the techniques marked bold are discussed.