Reduced harmonics PWM controlled line-side converter for electric drives

A reduced-harmonics pulse-width modulator and its application to the control of a three-level line-side power converter for a speed-variable AC drive are described. The pulse-width modulation scheme for the voltage source inverter determines each individual switching instant on the basis of a continuously updated volt-second balance between the reference vector and the actual switching state vector. The generated pulse sequence is shown to be asynchronous. The Fourier spectra are characterized by the absence of high-amplitude discrete carrier components. The emission of acoustic noise radiated from magnetic components is reduced. Experimental results have been obtained from a transistor converter operated from the 660 V industrial power supply. The DC-link voltage is 1200 V. With appropriate simplifications, the method is suitable for the control of two-level inverters as well.<>