Abstract: When the microgrid is operating in island mode，the cascaded H-bridge（CHB）converter as an

interface device may need to be configured with a non-sinusoidal reference wave of pulse width modulation（PWM）when implementing auxiliary functions such as negative sequence compensation. In order to avoid overmodulation，the positive sequence component in the PWM reference wave will be reduced，thereby reducing the maximum positive sequence of the converter output voltage. In this regard，a novel commonmode component injection technique was proposed to maximize the PWM linear modulation region.The new scheme can be implemented in real time without setting up a look-up table in the controller，that is，independent of the controller and compatible with any carrier-based PWM.At the same time，the new technology can be used for symmetrical or asymmetrical cascaded H-bridges，and when used with fault-tolerant PWM，it can realize fault-tolerant operation of the converter. The common mode injection PWMtests were carried out using the CHB converter prototype. The experimental results verify the effect of the new PMWlinearmodulation area amplification commonmode voltage injection technology.

      Key words: microgrid；cascaded H-bridge（CHB）converter；pulse width modulation（PWM）；common mode injection；linear modulation region