Polar control of current for PWM inverters

A new concept of output current control of a three phase PWM VSI feeding an AC motor drive is presented. Operation of the new regulator (controller) is based on the current and voltage vector description using polar coordinates. Six nonzero-voltage space vectors and two zero-voltage space vectors of the inverter output voltage have been applied. Taking the zero vectors into consideration enables the lowering of the switching frequencies of the inverter switches. The novel current control scheme ensures symmetry of the current and voltage waveforms, that cannot be achieved in schemes that apply the presentation of the rectangular coordinate systems, particularly referring to the range of work without modulation.