Minimum circulating water flow control method based on minimum frostproof allowable back pressure for indirect air-cooling system

The invention discloses a minimum circulating water flow control method based on a minimum frost-proof allowable back pressure for an indirect air-cooling system. The method comprises the following steps of primarily determining host circulating water flow and the frequency adjustment lower limit of a frequency variable host circulating pump according to a minimum host circulating flow influence factor; checking illogical limitation of host circulating pump frequency down-regulation, and recording the ambient temperature, condenser heat load, main steam flow, heat supply steam extraction flow,vacuum, and condenser outlet/inlet temperature before a test; gradually down-regulating the frequency of the host circulating pump according to the amplitude of 2 percent of a single pump when a unitoperates stably; in the gradual down-regulating process, continuously recording electrical and heat load, the power consumption of the host circulating pump, unit vacuum, the main steam flow and coalquantity, and checking whe