Development of variable voltage variable frequency drive system for induction motor speed control

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Problem statement 
Nowadays, more than 50% of electrical power is converted into mechanical energy by 
electric Motor. Because of certain benefits such as low cost, low maintenance, and its 
reliability, IM motors are commonly used in the industry for variable speed drive [5-
7]. Other than that IM motor, it has limited ability controlling its dynamic performance 
all but the crudest fashion. Besides, IM motor characteristics are non-linear, time 
varying and its complex system [8] which is requires a complex control circuit. 
Previously there are various techniques to control the motor speed such as changing 
the number of poles, voltage source control, or adding rheostat in the stator circuit. 
Changing the number of poles technique requires two separate windings in the stator 
that are electrically isolated from each other which makes the process controlling 
motor speed not smooth.
Besides that, voltage source control technique is also not efficient because it 
requires a large reduction in voltage when small change in speed is needed, which 
caused the motor overheating, and the speed is inefficient. Adding rheostat in the stator 

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circuit technique is almost not possible because torque must remain the same when 
power supply is decreased that caused slip increase and motor speed decreased [9]. 
Controlling the IM motor speed is necessary in the industry because the problem 
occurs at different speed changes and it is required for operating the machine. 
Conveyor is one of the AC motor applications. In the industry, conveyors often need 
the changing in the setting. In this situation, a monitoring system of the motor speed 
output is needed by controlling the motor speed [10].
Scalar control is known as the simplest and most robust way by controlling the 
IM motor [11]. The robust build of VVVF controller is a great benefit in industry that 
it has been attempted in [12]. Nevertheless, the real time controller requires particular 
attention for high performance IM motor [13]
.
By using appropriate real time 
microcontroller, the desired speed output of performance can be control precisely. 
Another problem is, eliminating the error induced by human error and inaccuracy in 
the interference. This issue often occurs at the hardware part, which is problem on the 
equipment. This caused several variables that will disrupt the component precision, 
like the conceptual structure in the supply part. The Texas Instrument TMS320F28335 
microcontroller is the device which is used to control the motor speed feedback 
behavior.
The benefits of this microcontroller are to enhance the efficiency of the closed 
loop designed for processing, sensing, and actuation. This speed control can be 
simulated based on MATLAB/Simulink software because it has graphical 
programming or instruction and easy to use. The speed of motor is be controlled by 
variable voltage variable frequency (VVVF) topologies using power electronic circuit 
and microcontroller. The target value of variable voltage variable frequency was be 
implemented inside LOOKUP table which generates the signal into the sinusoidal 
pulse width modulation (SPWM). Thus, this output from the inverter generates the 
suitable voltage and speed as at the desired speed reference value motor for the entire 
system of VVVF.
TMS320F28335 microcontroller has the ability in controlling SPWM signal 
and control the inverter output. The microcontroller sends the SPWM signal that 
operate the inverter through gate driver. At the meantime, this project the Proportional 
Integral (PI) controller received the output of closed loop feedback system from the 
motor speed and the error signal will be reduced to achieve the value of desired speed 
reference. 

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