Application introduction: Water supply application is very popular in Europe. In this case, constant pressure control is very important, the target of a pressure control system is to provide a variable flow with a constant pressure for the water system of an apartment building, machine refrigeration systems, mixing liquids in chemical industry, etc. PID control is needed in the constant pressure water supply applications. INVT can provide advanced software features to support different VFD series to be suitable for those water supply applications.
Keywords: PID control, GD20-EU, GD200A, GD300-16, Constant pressure control, Water supply, etc.
1.GD20-EU water supply application in Barcelona, Spain
1.1 Project introduction:
In Barcelona, the customer require to use only one drive to control three pumps, one variable frequency pump, two standby grid-frequency pumps. In order to keep enough pressure to sustain water supply, also to save the main pump’s life time, sometimes, need to make only one of those three pumps to work.
1.2 System configuration:
1#. GD20-7R5G-4-EU drive 1 pcs
2#. HMI 1 pcs
3#. One main pump, two auxiliary pumps
1.3 Application pictures
1.4 Logical sequence diagram:
1.5 Introduction of GD20-EU features
In this application, based on standard general purpose GD20-EU, use water-supply special firmware to meet customers’ requirements, the advanced software features is as follows:
1.Support auxiliary motor starting selection function for relay output. Add one more fan running mode selection: When the inverter is bigger than 0Hz, the fan runs. If it is equal to 0Hz or not run, the fan will stop running in 30 seconds.
2.Add P24 group special parameters for water supply application. Dormancy checking way support frequency and pressure. Add time-delay function while goes into dormancy. Dormancy wake-up method support frequency and pressure two ways.
3.Add the minimum dormancy time setting function: after the dormancy time, wake up again according to the dormancy wake-up mode.
4.Add the water supply function of “one inverter drag three motors” function: a variable frequency pump, two grid frequency pumps (auxiliary pumps), to complete the system of constant pressure water supply.
5.Support two sets of auxiliary motor startup time-delay and stop time-delay setting function.
6.Add the pressure hysteresis value of dormancy wake-up. Support the decimal point display number selection. Add the selection of two dormancy pressure units: BAR and %.
7.Add dormancy time-delay while goes into sleep for P01.19. Support PID given maximum value selection.
8.Add keypad display "SLP" function while in dormancy. Support keypad display "L" function while the set frequency is lower than low limit frequency.
2.GD200A water supply application in Athens, Greece
2.1 Project introduction:
In Athens, the end customer is a big food factory, it has its own water supply workshop, required pumps’ power range from 1.5kW to maximum 150kW, consider that most of those pumps not in constant torque control, V/F control and P type is enough. So we recommend the customer to use our GD200A drive, it can support G/P dual rating, and power maximum 500kW. For GD200A, it standard built-in simple water supply application, can be also used in fan application, in this case, in this food factory, if in winter not using water frequently, for several pumps, they can move the variable frequency drives to use them on fan applications. It can help customer to save a lot cost.
2.2 System configuration:
1#. GD200A-015G-4 drive 1 pcs
2#. HMI 1 pcs
3#. Enclosure with low voltage electrical equipments
M2 and M3 are auxiliary motors which are controlled by RO1 and RO2.
PID constant-pressure automatic control system is formed by the inverter through pressure feedback.
The pressure reference can apply analog or keypad input， Modbus communication protocol is also supported.
2.3 Application pictures
2.4 Short introduction of GD200A solution
For the customer, they can choose how much the water need whenever, for different water demands, the drive will work in different modes, PID control function is working all the time, and to avoid water hammer even no much water required, then deceleration stop, PID response quickly and stably.
Here below is one of the user defined software logics of setting parameters for reader reference:
*0% water demand: System stopped
*100% water demand: System starts - Pressure starts rising - Main pump reaches the maximum frequency - Pressure has not arrived to the set-point - AUX PUMP 1 activation elapsed time = P24.11 - AUX PUMP 1 is activated
*75% water demand: If the demand is reduced, the pressure increases, so the frequency will be reduced to maintain the pressure at the set-point - MAIN PUMP keeps regulating the frequency
*50% water demand: The demand is reduced again, so the frequency is also reduced to maintain the pressure at the desired set point - MAIN PUMP keeps regulating the frequency - AUX PUMP 1 stop time elapsed - AUX PUMP 1 is stopped
*25% water demand: The demand is reduced again, so the frequency is also reduced to maintain the pressure at the desired set-point - MAIN PUMP keeps regulating the frequency - AUX PUMP 2 stop time elapsed - AUX PUMP 2 is stopped
*0% water demand: The demand is reduced again, so the frequency is also reduced to maintain the pressure at the desired set-point - MAIN PUMP keeps regulating the frequency - MAIN PUMP frequency has decreased down to the Sleep Frequency. = P24.03 - MAIN PUMP sleep time delay = P24.05. As both AUX PUMPs are stopped, the MAIN PUMP can go to sleep now - SLEEP message must appear on the display until the inverter wakes up.
3.GD300-16 water supply application in Rotterdam, Netherlands
3.1 Project introduction:
In Rotterdam, the customer require to use double PID for temperature and pressure control, and need to control several pumps, maximum up to 6 pumps, so we suggest that they to use GD300-16 series HVAC VFDs, it have 2 PID controllers to get the desired pressure and real time clock which allows setting up to 5 working patterns. With GD300-16, a full control system for irrigation can be done without adding an external controller.
3.2 System configuration:
1#. GD300-16-030G/037P-4 drive 2 pcs
2#. Pumps up to 12 pcs PID control basic logic:
3.3 Application pictures
3.4 Short introduction of GD300-16 HVAC solution
1.Equipped with intelligent logic control, manual and soft start-up function
2.Support dual PID regulator, integrated with fan, water pump and conpressor control functions
3.Various HVAC-specific control function including fire override, timed cyclic control, dry run detection, constant torque, combination control of multiple sets of industry frequency conversion motors, sleep and wake-up function
4.Support BACnet, Profibus-DP, CANopen, DeviceNet communications
5.Support Real-time clock function and several pump control to extend the service life of pump
6.Standard C3 filters, CE or UL/cUL