Primary-frequency-modulation automatic switching control system based on power grid frequency

The invention discloses a primary-frequency-modulation automatic switching control system based on power grid frequency. The system comprises an analog quantity collector, a digital quantity collector, a first high-low-limit alarm module, a second high-low-limit alarm module, a first analog quantity generator, a second analog quantity generator, a first multiplier, a second multiplier, a divider,a logic or function module, a first function generator, a second function generator and an analog quantity selector. When the power grid frequency is greatly changed to cause that the slip signal of aunit exceeds a specified primary frequency modulation dead zone range, the unit automatically realizes switching of unequal rotating speed rates according to a power grid frequency abnormity emergency control instruction issued by a power grid or the slip signal locally acquired by the unit; and therefore, large primary frequency modulation overpower compensation for a power gap of the power gridis realized. According to