1. Customer needs
The customer has 4 sets of 37KW air compressors, three of which are installed in the same air compressor room, and the other is installed in a separate room 100 meters away, supplying gas to the same gas storage network. Now each air compressor operates independently. Hope to realize the following functions through the air compressor network control:
1. Start-stop control: 4 air compressors are started, loaded, unloaded and stopped in sequence to prevent the air compressors from starting at the same time and affecting the fluctuation of the power grid.
2. Pressure and flow control: The start and stop of the air compressor is based on the air demand. When the air pressure reaches the air pressure lower than the air demand, the air compressor will start another one. When the pressure is excessive and reaches the unloaded state, the air compressor automatically reduces by one. If the on-site pressure has reached the requirement, the current number of air compressors on is maintained.
3. Air compressor rotation: When the air compressors are started, the starting sequence can be changed to each other, which fully consumes the consumables use time of each air compressor and the average use of consumables.
Two, transformation plan
In response to customer requirements, we adopt the following networking control solutions:
In order to realize the networking of all air compressors so that the air compressors use the same communication protocol, during the implementation of the plan, all air compressor controllers must be replaced with controllers that support the same communication protocol, so that all air compressors can be implemented Synchronous communication. Set the address code of each machine separately. Use the 485 half-duplex communication method to connect each machine according to the following connection method. Realize network connection. Set one of the air compressors as the main engine (preferably one of the three installed together). The others are slaves, and the slaves are numbered and the addresses are set in sequence according to the arrangement sequence.
The connection diagram is as follows:
Slave------2#, 3#, 4#
We now assume that the starting sequence of the slaves is from 2# to 4# (the actual starting is determined by the operating time of each air compressor, and the air compressor with the least operating time starts first)
1. Operation of joint control
Start operation: set to the joint control state, in the standby state of all machines, the host starts and enters the air pumping state. After the set linkage delay time is reached, if the pressure does not meet the pressure requirement, then 2# starts to start and enters the air pumping state. At this time, the linkage delay time is reached, and the pressure still does not meet the gas demand. At this time, the 3# air compressor will start, and so on, until the 4# air compressor also starts. If after the 2# air compressor is turned on, the pressure value has met the gas demand, then the 3# and 4# air compressors will not start until the pressure is lower than the set joint control pressure requirement. During the startup process, if one of the air compressors is not powered on, the system will bypass this air compressor and continue the startup process. When other air compressors are already in operation, this air compressor is powered on. After the controller is initialized, if the air pressure is lower than the loading pressure of the joint control, the air compressor will automatically start and join the joint control state . Starting the number of air compressors according to the gas demand is conducive to the stability of the air pressure, meeting the demand for changes in the air pressure, and saving electricity. The loading process of the air compressor does not change in the loading state. After the air compressor is started, it is loaded according to the pressure requirements of the joint control. During the loading process, all machines will use the host pressure as the testing standard. When the pressure is lower than the joint control pressure, it is the loading state. When the pressure is higher than the joint control pressure, it is unloaded.
Unloading state: When the pressure is higher than the combined control pressure, the system will find out the air compressor with the longest running time according to the operating time of each air compressor to give priority to unloading, and so on until all the air compressors enter the unloading state. If one of the air compressors is unloaded and the pressure is lower than the unloading pressure of the joint control, and higher than the loading pressure of the joint control, the other air compressors will no longer enter the unloading state, while maintaining the air compressor combination to continue running.
Stop state: In the joint control state, if the host is manually turned off, the joint control system will be shut down. Sleeping state: The air compressor enters the unloading state and exceeds the time required by the empty vehicle for too long. The air compressor enters the dormant state, and the machine stops running. The air compressor will automatically start until the pressure is lower than the loading pressure requirement of the joint control.
Air compressor rotation status: Assuming that the current 1#, 2#, 3# air compressors are in operation and the pressure meets the requirements, the 4# air compressor is in standby or empty for too long, assuming that the 3# air compressor is continuous The running time meets the rotation time requirement. At the next start, the 4# air compressor will start, and the 3# air compressor will enter the shutdown state, and so on, the other air compressors will be rotated respectively. If 4#, 2# air compressors are in standby or empty for too long, then 2#, 4# air compressors will replace other air compressors up to the rotation time. If there are more air compressors in the 4# air compressor is in standby or empty for too long. The rotation method is as above. This mode of operation is beneficial and makes full use of the running time of the consumables, and avoids uneven usage of the consumables.
2. Stand-alone operation
When the main engine is not started, the air compressor slave machine is started separately. At this time, the running state is a stand-alone operation, and its loading and unloading pressures act according to the loading and unloading pressure values set by the air compressor.
Four, control characteristics:
When starting the network, the user only needs to turn on the host, and the slaves will start up according to pressure requirements.
Air compressors with less running time are started first, and air compressors are used in a balanced way, saving maintenance costs. Avoid the impact of the air compressors on the power grid when the air compressors are started at the same time.
Start the air compressor according to the gas demand to avoid waste of electricity.
The joint control and single machine control are easy to switch, and the main engine is stopped. Other air compressors will run with the single machine without changing any wiring and settings, and the operation is convenient.
The system comes with a rotation function, and then runs automatically to switch, so that the air compressor consumable time is averaged.
Joint control structure helps to control the pressure smoothly
The workshop stopped using air, and the air compressor system controlled all the machines to shut down by itself. When air was used again, the air compressor unit started again.
The system adopts the standard MODBUS II communication protocol, and the network structure is stable.
5. Transformation effect:
Take the data of an air compressor observed on site as an example:
From installation to use of this controller:
The machine's no-load running time is = total running time-load running time = 18308-10944 = 7364 hours
Generally, the no-load current is about 40A.
Therefore, it can save power = 40A*380V*7364H/1000 = 111932.8 degrees
The industrial electricity price is about 0.6 yuan/kWh, calculated based on the 90% reduction in energy consumption after unloading after the transformation:
Savings amount = 111932.8*0.6*90%=60443.28 yuan