Thermal auxiliary system suitable for quick start and stop of pulverized coal once-through boiler and control method

The invention belongs to the technical field of boilers, and particularly relates to a heat auxiliary system suitable for quick start and stop of a pulverized coal once-through boiler and a control method. The system comprises a first pipeline, a second pipeline, a third pipeline and a fourth pipeline, a section of pipeline is led out from a pipe section from an adjacent high-temperature superheater to a steam turbine and is connected to a pipe section from the high-temperature superheater to the steam turbine of the unit; a section of pipeline is led out from the outlet header of the low-temperature superheater of the adjacent boiler to be connected to the inlet header of the low-temperature superheater of the unit; the third pipeline is connected to a bypass of a water supply pipeline of the unit after one section is led out from an outlet header of an adjacent boiler economizer and a steam pipeline of a separator outlet; and one section of the fourth pipeline is led out from the inlet header of the low-tem