AC motors(Alternating Current motors) have a simple structure and has higher efficiency than the DC
motors(Direct Current motors) when operated at high speed. AC motors also provide more durable
service with a lower cost compared to DC motors. Besides, AC motors can easily be supplied directly
from the grid and therefore they are widely used in industry. However, when it is directly connected to the
grid, traditional AC motor gets the better performance only at the speed near the synchronous speed due
to its working principle . In some low cost applications where only DC is available, e.g. in electrical
vehicles, the usages of AC motors are limited.
For a variable-speed application or if the power source is DC, a variable-speed driver is needed, which is
usually realized with a three-phase inverter(DC-to-AC converter).With feedback or estimation of the field
orientation, AC motors can be modeled as a separately magnetized DC motor through a series of coordinate
transformations based on the orientation. For the transformed AC motor model, DC motor control methods
can be applied, which can obtain good transient performance and eliminate oscillation in the produced
torque . This method of controlling the transformed AC motor is called vector control.
Mostly, an embedded microcontroller governs the overall operation of AC motor controller. Among
various microcontrollers, Digital Signal Processor(DSP) can perform complicated computation, such as
coordinate transformations, field estimation algorithms and controller algorithms. Before implementing the
vector control system on the microcontroller, the control algorithm could be verified with the help of the
simulation softwares, such as Matlab/Simulink.