A Method to Compensate for the Distortion of the Output Voltage of an H-Bridge Inverter Under Sinusoidal Unipolar PWM

The output voltage of an inverter (output of the LC filter) significantly deviates from the ideal sinusoidal waveshape under sinusoidal unipolar pulse width modulation with a sinusoidal modulating signal. Due to the error between desirable and practical waveshape of the output voltage, the total harmonic distortion deteriorates. To compensate for the distortion, the existing approach requires a lot of computational efforts to correct the pulse width of each gate pulse over an entire fundamental AC period. This paper proposes a simple method to reshape the modulating signal based on the predicted error signal in the rotating frame of reference. The proposed technique is validated experimentally on a DQ-controlled IGBT-based inverter module operating at 500 W, 110 V. The experimental results show an improvement in THD of the output voltage by approximately 5%.