Soft starting method improved based on H-bridge cascade STATCOM (Static Synchronous Compensator)

The invention relates to a soft starting method improved based on an H-bridge cascade STATCOM (Static Synchronous Compensator). The method is characterized by comprising the main steps of: accessing a current-limiting resistor in series during starting of the STATCOM, controlling pulse signals of all unit switch devices so as to absorb active power provided by a power grid to the greatest extent, and pre-charging a device; removing the current-limiting resistor after pre-charging is completed, and forwarding the device into an idle running period; providing a voltage given value of a DC side by a voltage gradually-increasing method during idle running period; and stably increasing the voltage of the DC side into the given value; forwarding into a load running period and completing the starting process. According to the soft starting method of the device, provided by the invention, the pulse signal of all unit switch devices are controlled from a pre-charging period, harmonic distortion rate of the output curr