Output Waveform Distortion Suppression Method of Asymmetric Sine Wave Inverter Based on Online Identification and Linearization of System Transmission Characteristics

Limited by the switching frequency of an insulated gate bipolar transistor (IGBT), the system bandwidth of high-power inverters is low. If the amplitude and phase changes of each harmonic from the reference signal to the output waveform are defined as transmission characteristics, it can be concluded that the limited bandwidth will result in nonlinear system transmission characteristics. This results in the amplitude and phase distortion of each harmonic of the asymmetric sine wave, which in turn leads to severe distortion of the output waveform. Therefore, this article proposes a method to linearize transmission characteristics. This method effectively offsets the nonlinear effect of transmission characteristics, which is caused by the limited bandwidth, by causing distortions with respect to each harmonic in the reference signal, thereby suppressing the distortion of the output waveform. In addition, an online identification method of transmission characteristics based on a state observer is proposed to achieve the online linearization of system transmission characteristics. This method does not rely on closed-loop system control, has no stability problems, and can be used for a variety of control methods. Simulation and experiments verify the effectiveness of this method.