三相H桥三电平逆变器谐波抑制方法

Harmonic suppression of three-phase three-level inverter with H bridges

为改善传统三相H桥三电平逆变器输出线电压质量,对存在的直流母线电压波动和线电压相邻"电平层"交叠现象进行理论分析。提出基于直流母线电压实时采样的载波前馈校正方法,根据直流母线电压的波动实时校正载波形状,调整不同PWM脉冲幅值时的脉宽;提出锯齿载波相移PWM(PS-SPWM)调制方法,控制任意两相电压相对应的脉冲对始终位于对应锯齿载波的起始(末尾)处,消除了线电压相邻"电平层"交叠现象。与传统方法相比,进一步抑制了线电压的高、低次谐波。实验结果验证了提出方法的可行性与有效性。

In order to improve the line-to-line voltage quality of three- phase three- level inverter with H bridges,the phenomenon of DC- link ripples and the neighboring layer overlapping of line- to- line voltage are analyzed theoretically. The carrier feedforward emendation based on Sampling DC voltage in real time is proposed. The PWM pulse width with different amplitudes is modified according to the modified carrier. The modulation of PS-SPWM with sawtooth carrier is presented,which makes the pulse pair of arbitrary two phase voltages stand at the beginning or ending of the respective sawtooth carrier to eliminate the line- to -line voltage overlapping. The lower and higher order harmonics are further suppressed compared with traditional methods. The experimental results verify the validation of proposed method.