Abstract: The variable frequency reformation scheme for primary air fan and induced draft fan of CFB boiler in Yunnan Huadian Xunjiansi Power Generation Corporation Limited using highvoltage frequency converter with automatic bypass function was introduced. The modification of the control logic and the picture of DCS and the automatic control function optimization were expounded emphatically. After the variable frequency reformation of the primary air fan and the induced draft fan, the thermal control logic is perfect, the automatic control function can put into operation normally, the fan operation state can be switched over from variable frequency to power frequency or otherwise automatically. When the frequency converter is failure, the fan operation state will be switched over automatically to power frequency without turbulence and the unit load will not be impacted. The energy saving effect of the reformation is obvious.

Key words: induced draft fan, primary air fan, high voltage variable frequency reformation, thermal control logic, automatic control function