Current-Ripple Prediction for Three-Phase PWM Converters

The three-phase pulsewidth-modulation (PWM) converter is one of the most widely used topologies for power conversion. In order to design PWM methods, the influence of PWM methods on the current ripple is needed. This paper studies the current ripple of a three-phase PWM converter with general PWM methods for the design and control of this kind of converter. The current ripple is analyzed with eight different Thevenin equivalent circuits for the eight different voltage vectors. Then, the current-ripple slope and effective time could be achieved for every period. The current ripple could be predicted with both peak and rms values. Analytical predicted results show that discontinuous PWM could generate obviously bigger current ripples than space vector PMW for both peak and rms values with the same conditions. Simulation and experiments are built to verify the analytical results, proving that the theoretical prediction is valid. This analysis provides the basis for the design and control of the PWM method for converters.