Waveform flat-topping unit

A waveform flat-topping unit comprising:

• means for producing first, second and third reference signals of a stationary frame;
• means for producing fourth and fifth reference signals of a rotating frame, where both the fourth and fifth reference signals correspond to a difference between the first and third reference signals;
• a normalizing unit for normalizing the first reference signal;
• means for generating a third harmonic waveform of the normalized first reference signal;
• means for producing a vector value according to the fourth and fifth reference signals;
• means for comparing the vector value to a predetermined threshold value;
• means, responsive to the comparing means, for adding zero to each of the first, second and third reference signals when the vector value is less than or equal to the predetermined threshold value;
• and
• means, responsive to the comparing means, for adding the third harmonic waveform to each of the first, second and third reference signals when the vector value is greater than the predetermined threshold value.