1 Digital PFC and Motor Control
The majority of motor control systems often use PFC as the first stage of the system. Without an input PFC stage, the current drawn will have significant harmonic content due to the presence of switching elements of the inverter. In addition, since motor loads are highly inductive, the input currents will induce significant reactive power into the input system, thereby reducing overall efficiency of the system. A PFC stage which is a front-end converter of a motor control application, provides better output voltage regulation and reduces harmonic content of the input current drawn. The standard boost converter topology with average current mode control is the preferred method for implementing digital PFC in these applications.
The PMSM is driven in Speed Control mode using the Dual Shunt Sensorless FOC method. The Sensorless FOC technique overcomes restrictions placed on some applications that cannot deploy position or speed sensors. The speed and position of the PMSM are estimated by measuring phase currents. With a constant rotor magnetic field produced by a permanent magnet on the rotor, the PMSM is very efficient when used in appliances. When compared with induction motors, PMSMs are more powerful for the same given size. They are also less noisy than DC motors, since brushes are not involved. Therefore, the PMSM is chosen for this application.