Control system applied to inlet water temperature of low-temperature economizer

The invention discloses a control system applied to the water temperature of an inlet of a low-temperature economizer. Comprising a third switching value DI input module, a fifth analog quantity AI input module, a sixth analog quantity AI input module, a seventh analog quantity AI input module, an eighth analog quantity AI input module, a first small value judging device, a sixth analog quantity AI input module, a seventh analog quantity AI input module, a subtracter, a third analog quantity AO output module and a third small value judging device. When the logic value output by the first logic AND module is 1, the logic value input by the first switching value DO output module is 1; the first switching value DO output module sends the logic value to a B adjusting valve control loop to realize control of a B adjusting valve; and when the logic value output by the second logic AND module is 1, the second switching value DO output module sends the logic value to an A adjusting valve control loop, so that the A a