Aiming at the case of large frequency fluctuation in natural gas unit black start project

combining with the gas black start system and the waveform diagram during static frequency convertor(SFC) startup

the failure phenomenon is described in detail and the specific cause of the failure is analyzed. On the basis of considering the slow response speed of diesel generator unit

a super capacitor-assisted black start frequency modulation(FM)strategy is proposed. The SFC power is divided into base power and frequency fluctuation power

among which the base power is borne by the diesel generator unit to ensure stable operation of the system

and the frequency fluctuation power is quickly responded by the supercapacitor to suppress the frequency fluctuation effectively.Through the black start experiment of a 4F gas unit

the strategy not only effectively reduces the frequency fluctuation during the black start process

but also avoids the overcurrent fault during ramp-up and load-change phase

thus the reliability and safety of black start of the gas unit is improved.