Variable frequency air source heat pump cold water unit and parallel control method thereof

Abstract

A control method includes: setting a set water temperature for each subunit, acquiring a total outlet water temperature; according to an operating mode of the unit, judging whether the total outlet water temperature meets a first unloading condition, and if so, controlling the subunit with the lowest operating frequency to perform an unloading action; acquiring the total outlet water temperature in real time, and judging whether the total outlet water temperature meets a second unloading condition, and if so, controlling the subunit with the lowest operating frequency to perform the unloading action; judging whether the total outlet water temperature meets a start-up loading condition in real time, and if so, controlling the first subunit with the shortest accumulative operating time of the subunits performing the unloading action to perform a start-up loading action; and judging whether the total outlet water temperature meets the start-up loading condition every a specified time.

1 . A parallel control method of a variable frequency air source heat pump cold water unit, wherein the variable frequency air source heat pump cold water unit comprises a plurality of subunits disposed in parallel, the parallel control method comprising the steps of:
 setting a set water temperature of each of the subunits, and acquiring a total outlet water temperature of the variable frequency air source heat pump cold water unit;   according to an operating mode of the variable frequency air source heat pump cold water unit, judging whether the total outlet water temperature meets a first unloading condition, and if so, controlling the subunit with the lowest operating frequency to perform an unloading action; the first unloading condition being: in a heating/domestic hot water mode, the total outlet water temperature≥the set water temperature−(a number of subunits turned on−a first preset value); and in a cooling mode, the total outlet water temperature≤the set water temperature+(a number of subunits turned on−a second preset value);   acquiring the total outlet water temperature in real time, and judging whether the total outlet water temperature meets a second unloading condition, and if so, controlling the subunit with the lowest operating frequency to perform the unloading action;   judging whether the total outlet water temperature meets a start-up loading condition in real time, and if so, controlling the first subunit with the shortest accumulative operating time of the subunits performing the unloading action to perform a start-up loading action; and   judging whether the total outlet water temperature meets the start-up loading condition every a specified time, and if so, controlling the subunit to perform the start-up loading action, the subunit performing the start-up loading action being shut down according to conditions in a non-parallel mode.   
     
     
         2 . The parallel control method of the variable frequency air source heat pump cold water unit according to  claim 1 , wherein the start-up loading condition is: in the heating/domestic hot water mode, whether the total outlet water temperature is not higher than the set water temperature, and whether the total outlet water temperature has risen within a first preset time period, and if the total outlet water temperature is not higher than the set water temperature, and the total outlet water temperature has not risen within the first preset time period, the first subunit with the shortest accumulative operating time of the subunits performing the unloading action is controlled to perform the start-up loading action; and
 in the cooling mode, whether the total outlet water temperature is not lower than the set water temperature, and whether the total outlet water temperature has fallen within a second preset time period, and if the total outlet water temperature is not lower than the set water temperature, and the total outlet water temperature has not fallen within the second preset time period, the first subunit with the shortest accumulative operating time of the subunits performing the unloading action is controlled to perform the start-up loading action.   
     
     
         3 . The parallel control method of the variable frequency air source heat pump cold water unit according to  claim 1 , wherein the second unloading condition is: in the heating/domestic hot water mode, the total outlet water temperature rises by a first specified temperature; and in the cooling mode, the total outlet water temperature falls by a second specified temperature. 
     
     
         4 . The parallel control method of the variable frequency air source heat pump cold water unit according to  claim 1 , further comprising: judging whether the total outlet water temperature meets the maximum water temperature/minimum water temperature limiting conditions, and if not, performing a “shut-down for temperature-reaching” process. 
     
     
         5 . The parallel control method of the variable frequency air source heat pump cold water unit according to  claim 1 , further comprising: judging whether the subunit meets “shut-down for power-off”/“shut-down for temperature-reaching” conditions, and if so, sequentially unloading one subunit every a specified time according to the accumulative operating time of the subunit. 
     
     
         6 . The parallel control method of the variable frequency air source heat pump cold water unit according to  claim 1 , further comprising a start-up control logic:
 according to the operating mode of the variable frequency air source heat pump cold water unit, judging whether the total outlet water temperature meets a first start-up condition, and if so, turning on the subunit in a shut-down state with the shortest accumulative operating time; and   acquiring the total outlet water temperature every a first specified time, and judging whether the difference between the total outlet water temperatures of adjacent time intervals meets a second start-up condition every a second specified time, and if so, turning on the subunit in the shut-down state with the shortest accumulative operating time; and if not, not turning on the subunit.   
     
     
         7 . The parallel control method of the variable frequency air source heat pump cold water unit according to  claim 6 , wherein the first start-up condition is: in the heating/domestic hot water mode, the total outlet water temperature≤the difference between the set water temperature and a third preset value; and in the cooling mode, the total outlet water temperature≥the sum of the set water temperature and a fourth preset value; and
 the second start-up condition is: in the heating/domestic hot water mode, the total outlet water temperature≤the difference between the set water temperature and the third preset value, and the difference between the total outlet water temperatures≤a first temperature threshold; and in the cooling mode, the total outlet water temperature≥the sum of the set water temperature and the fourth preset value, and the difference between the total outlet water temperatures≥a second temperature threshold. 
 
     
     
         8 . The parallel control method of the variable frequency air source heat pump cold water unit according to  claim 6 , further comprising: acquiring the total outlet water temperature every 5 min, and judging whether the difference between the total outlet water temperatures meets the second start-up condition every 30 min, and if so, turning on the subunit in the shut-down state with the shortest accumulative operating time; and if not, not turning on the subunit. 
     
     
         9 . The parallel control method of the variable frequency air source heat pump cold water unit according to  claim 6 , wherein if the difference between the total outlet water temperatures or the total outlet water temperature does not meet any of the start-up conditions for a specified time, and no unloading action of the subunit is detected during the specified time, one subunit with the shortest accumulative operating time is forcibly turned on. 
     
     
         10 . A variable frequency air source heat pump cold water unit, which performs the parallel control method of the variable frequency air source heat pump cold water unit according to  claim 1 .