Abstract: Circuits and methods for use with an integrated circuit chip having internal back EMF estimation to control a permanent magnet synchronous motor includes an AC current feedback circuit, a scaling circuit, and a current regulator. Additionally, a speed regulator may be employed. In one embodiment, during operation at very low speed, the speed regulator is in an open loop control mode due to a back EMF detection limitation of the IC chip, and only the current regulator is active. A feedback current signal, together with a user-defined command current signal, serves the input of the current regulator, which controls the AC motor current and drives the motor speed from standstill. Once the motor speed reaches a certain level, the measured back EMF from the IC chip is sufficient to estimate the motor speed, which is compared with a user-defined command speed, and an error of the these two signals provides the input of a speed regulator.

Abstract: In one embodiment, a harmonic feedback system is characterized by: a three-phase to two-phase transformer configured to convert an output fundamental frequency current from a distributed power system and to convert the output fundamental frequency current from a three-phase current to a two-phase stationary reference current; a harmonic frequency transformer configured to convert the two-phase stationary reference current to a synchronous reference current, said harmonic frequency transformer having a target synchronous reference frame frequency based upon a reference harmonic current of the output fundamental frequency current; at least one filter device configured to remove predetermined components from the synchronous reference current to output a harmonic feedback current; a summation component to compare the harmonic feedback current with the reference harmonic current and to output a harmonic error current for driving the distributed power system to produce the output current.