Two-control multi-constant-pressure water supply equipment control system and control method thereof

[0061] Examples:

[0062] See figure 2 (FR1, FR2, and FR3 in the figure are thermal relay protection devices), take the start and stop process of three water pumps as an example:

[0063] When the system just starts to run, turn on the No. 5b inverter 5 and turn off the No. 5c inverter 5. At the same time, turn on the No. 2b water pump 2 in variable frequency mode (the first contactor 7 on the No. 2b water pump 2 is sucked in, and the second contact is Device 8 is disconnected) connected to the system, and the rest of the water pump 2 is not connected; within the pressure range that a water pump 2 can provide, the No. 5b frequency converter 5 drives the No. 2b water pump 2 for frequency conversion operation, and the control unit 6 directs according to the water pressure data. No. 5b inverter 5 dynamically outputs control signals;

[0064] As the water consumption increases, the control unit 6 according to the preset threshold (the threshold will be delayed for a certain time), before the 2b water pump 2 reaches full load operation (at this time, the speed of the 2b water pump 2 still has a certain increase. Connect No. 2c water pump 2 to the system in variable frequency mode (the first contactor 7 on No. 2c water pump 2 is closed, and the second contactor 8 is disconnected), and at the same time, start No. 5c frequency converter 5 and No. 2c water pumps 2Complete the soft start; among them, before the two pumps 2 reach the same speed, the speed of No. 2c pump 2 will increase from 0 in one direction. When the speed of No. 2c pump 2 is rising, the speed of No. 2b pump 2 will be increased. It is used to continue to compensate for the demand for water pressure at the water end, effectively reducing the water pressure fluctuations when the number of pumps 2 is increased; the control unit 6 always dynamically outputs control signals to the No. 5b inverter 5 according to the water pressure data, and at the same time, the control unit 6 Output the same control signal to No. 5c inverter 5 as No. 5b inverter 5; when the speed of the two pumps 2 reach the same, No. 2c pump 2 and No. 2b pump 2 are under the control signals of the two inverters 5. Frequency conversion operation, two water pumps 2 have the same speed;

[0065] If the water consumption continues to rise, the control unit 6 according to the preset threshold (the threshold will be delayed for a certain time), before the two pumps 2 reach full load operation (at this time, the speed of the two pumps 2 is still a certain amount) Increase margin), turn off the No. 5b inverter 5, and at the same time switch the No. 2c water pump 2 to the industrial frequency mode (the first contactor 7 on the No. 2c water pump 2 is disconnected, and the second contactor 8 is closed). Unit 6 outputs the power frequency control signal to No. 2c water pump 2, and No. 2c water pump 2 operates at power frequency; Turns No. 2d water pump 2 in variable frequency mode (the first contactor 7 on No. 2d water pump 2 is sucked in, and the second contactor 8 Disconnect) Connect to the system, and then start No. 5b inverter 5, No. 2d pump 2 completes soft start, No. 2d pump 2 and No. 2b pump 2 are operated under the control signals of two inverters 5, No. 2c pump 2 Power frequency operation under the action of the power frequency signal of the control unit 6; the speed increase process of No. 2d water pump 2 is the same as before; during the speed increase process of No. 2d water pump 2, No. 2b water pump 2 is continuously operating at variable frequency, at this time, 2b The speed increase margin of the No. water pump 2 plays a role, so that when the water pump 2 is added, the fluctuation of the water pressure at the outlet end of the water pump 2 is reduced, and the water supply pressure is more stable. If it is a one-control-multi-control system, when the number of water pumps 2 is increased, when the speed of the newly started water pump 2 rises, because there is no continuous frequency conversion operation of the water pump 2, the water pressure fluctuates greatly, and sometimes even water heaters, boilers, etc. The equipment causes damage.

[0066] When the water consumption drops, the speed of the water pump 2 in the variable frequency mode is reduced under the PID adjustment, and the control unit 6 detects that the water pump 2 in the variable frequency mode reaches the reduced pump frequency (after reaching the reduced pump frequency, there is a certain delay), then proceed Pump reduction operation: first increase the speed of No. 2b pump 2 and No. 2d pump 2, and then turn off the power of No. 2c pump 2. The increase in speed of No. 2b pump 2 and No. 2d pump 2 is due to sudden shutdown of No. 2c The impact of water pressure drop caused by water pump 2 is compensated;

[0067] When the water consumption continues to drop and the number of pumps 2 needs to be reduced from 2 to 1 (that is, the operating frequency of pump 2 in variable frequency mode reaches the reduced pump frequency), turn off one of the pumps 2 and one of the inverters 5 , The closed water pump 2 stops in the frequency conversion mode to avoid the occurrence of water hammer effect.