A self-balancing space vector switching modulator for three-level motor drives

This paper describes how to formulate a self-balancing space vector modulator for the three-level neutral point clamp topology typically used for high power induction motor drives. Besides space vector modulation principle is used to calculate pattern times within one control update cycle, several other techniques are proposed in order to obtain a production quality modulator. These include a pivot point concept to be used for pattern selections in order to achieve minimum switching losses, techniques for neutral point voltage balancing, power device minimum on/off time guarantee, adjacent state switching, and sine triangular equivalent etc. Lab test results are given for effectiveness of the modulator.