Control system and method for controlling a water supply from at least two separate input lines into a sector of a water supply network

Abstract

A control system (15) controls a water supply from at least two separate input lines (3i-k) into a sector (1) of a water supply network. The control system (15) is configured to receive input flow information indicative of the water input flow (q.sub.i-k) through each of the input lines (3i-k). The control system (15) is configured to receive input pressure information indicative of the input pressure (p.sub.i) in at least one (3i) of the input lines (3i-k). The control system (15) is configured to receive pressure information indicative of at least one pressure value (p.sub.cri,m,n) determined by a pressure sensor (7m,n) within the sector (1). The control system (15) is configured to control the input pressure (p.sub.i) by controlling at least a pressure regulating system (13i) at an input line (3i) based on the input flow information from all input lines (3i-k) and based on the sector pressure information.

Claims

1. A control system for controlling a water supply from at least two separate water input lines into a sector of a water supply network, wherein the control system is configured to: receive input flow information indicative of water input flow through each of the input lines; receive input pressure information indicative of input pressure in at least a first input line of the at least two separate water input lines; receive sector pressure information indicative of at least one pressure value determined by at least one pressure sensor within the sector of the water supply network; and generate at least one control output to control the input pressure by controlling at least a first pressure regulating system at the first input line based on the received input flow information from each of the input lines and based on the received sector pressure information.

2. The control system according to claim 1, wherein the control system is configured to decrease the input pressure until a lowest pressure value of the at least one pressure value determined by the at least one pressure sensor within the sector has dropped to a required minimum sector pressure.

3. The control system according to claim 1, wherein the control system is configured to generate at least one control output to control a contribution of the input flow through each of the input lines to the total input flow of all input lines according to an associated weight factor for each of the input lines to obtain a desired mix of input flows.

4. The control system according to claim 1, wherein the control system is configured to: receive input pressure information indicative of the input pressure at each of the input lines; generate at least one control output to control a pressure regulating system in each input line to control the input pressure in each of the input lines based on the input flow information from all input lines, the input pressure information from all input lines, and the sector pressure information.

5. The control system according to claim 1, wherein: the control system comprises a first input control module for controlling the first pressure regulating system, wherein the first input control module is configured to receive the input flow information from all input lines and to receive a parameter set [A, B] and to generate the at least one control output for setting the input pressure at the first input line to p.sub.set=Aw.sup.2Q.sup.2+B; Q is the total input flow of all input lines; and w is a weight factor for the flow contribution of the first input line to the total input flow of all input lines.

6. The control system according to claim 1, wherein: the control system comprises a plurality of input control modules, wherein each of the plurality of input control modules is for a corresponding one of the input lines for controlling an associated pressure regulating system at each of the input lines; each input control module is configured to receive the input flow information from all input lines and to receive a parameter set [A.sub.i, B.sub.i] for setting the input pressure at a corresponding one (i-th) of the input lines to p.sub.set,i=A.sub.iw.sub.i.sup.2Q.sup.2+B.sub.i; Q is the total input flow of all input lines; and w.sub.i is a weight factor for the flow contribution of the i-th of the input lines to the total input flow of all input lines.

7. The control system according to claim 1, wherein: the control system comprises a sector control module for receiving the input flow information from individual ones (i-th) of the input lines and the sector pressure information; the sector control module is further configured to update and provide a parameter set [A.sub.i, B.sub.i] for the input pressure at each of the input lines to be set to p.sub.set,i=A.sub.iw.sub.i.sup.2Q.sup.2+B.sub.i; Q is the total input flow of all input lines; and w.sub.i is a weight factor for the flow contribution of the i-th of the input lines to the total input flow of all input lines.

8. The control system according to claim 1, wherein the input flow information from each of the input lines comprises input flows through each of the input lines and an expected trend in the total flow of all input lines, in a form of a Kalman filter state vector.

9. The control system according to claim 1, wherein: the control system generates the at least one control output to control at least a first pressure regulating system at the first input line based selectively on a short-term prediction or a long-term prediction of the input flow information from all input lines; a criterion for selecting either the short-term prediction or the long-term prediction is a time period that has lapsed since a latest successful receiving of input flow information from all input lines.

10. The control system according to claim 9, wherein the short-term prediction is based on applying a recursive filter on the input flow information from all input lines.

11. The control system according to claim 9, wherein the long-term prediction is based on applying a Fourier transformation on the input flow information from all input lines and recursively updating a truncated Fourier Series for approximating an expected periodic long-term behavior.

12. A method for controlling a water supply, from at least two separate input lines, into a sector of a water supply network, the method comprising the steps of: receiving input flow information indicative of the water input flow through each of the input lines; receiving input pressure information indicative of the input pressure in at least a first one of the input lines; receiving sector pressure information, indicative of at least one pressure value determined by at least one pressure sensor within the sector of the water supply network; and controlling the input pressure by controlling at least a first pressure regulating system at the first input line, based on the input flow information from all input lines and based on the sector pressure information.

13. The method according to claim 12, further comprising the step of decreasing the input pressure until a lowest of the at least one pressure value determined by the at least one pressure sensor within the sector has dropped to a required minimum sector pressure.

14. The method according to claim 12, further comprising the step of controlling a contribution of the input flow through each of the input lines to the total input flow of all input lines according to an associated weight factor for each of the input lines to obtain a desired mix of input flows.

15. The method according to claim 12, further comprising the steps of: receiving input pressure information indicative of the input pressure in all other input lines; and controlling the input pressure in each of the input lines by controlling all other pressure regulating systems at all other input lines based on the input flow information from all input lines, the input pressure information from all input lines, and the sector pressure information.

16. The method according to claim 12, further comprising the step of locally controlling the first pressure regulating system, wherein: the input flow information from all input lines and a parameter set [A, B] is received and the input pressure at the first input line is set to p.sub.set=Aw.sup.2Q.sup.2+B; Q is the total input flow of all input lines; and w is a weight factor for the flow contribution of the first input line to the total input flow of all input lines.

17. The method according to claim 12, further comprising the step of locally controlling an associated pressure regulating system at each of the input lines, wherein: the input flow information from all input lines and a parameter set [A.sub.i, B.sub.i] is received and the input pressure at each (i-th) of the input lines is set to p.sub.set,i=A.sub.iw.sub.i.sup.2Q.sup.2+B.sub.i; Q is the total input flow of all input lines; and w.sub.i is a weight factor for the flow contribution of the i-th of the input lines to the total input flow of all input lines.

18. The method according to claim 12, further comprising the steps of: remotely updating and providing a parameter set [A.sub.i, B.sub.i]; and setting the input pressure at each (i-th) of the input lines to p.sub.set,i=A.sub.iw.sub.i.sup.2Q.sup.2+B.sub.i; Q is the total input flow of all input lines; and w.sub.i is a weight factor for the flow contribution of the i-th of the input lines to the total input flow of all input lines.

19. The method according to claim 12, wherein the input flow information from each of the input lines comprises input flows through each of the input lines and an expected trend in the total flow of all input lines in a form of a Kalman filter state vector.

20. The method according to claim 12, wherein: the step of controlling the input pressure by controlling at least a first pressure regulating system at the first input line comprises selecting either a short-term prediction or a long-term prediction of the input flow information from all input lines; and a criterion for selecting either the short-term prediction or the long-term prediction is a time period that has lapsed since a latest successful receiving of input flow information from all input lines.

21. The method according to claim 20, wherein the short-term prediction is based on applying a recursive filter on the input flow information from all input lines.

22. The method according to claim 20, wherein the long-term prediction is based on applying a Fourier transformation on the input flow information from all input lines and recursively updating a truncated Fourier Series for approximating an expected periodic long-term behavior.

23. A water supply system for supplying water from at least two separate input lines into a sector of a water supply network, the water supply system comprising: a pressure regulating system at each of the at least two separate input lines, wherein each pressure regulating system is configured to provide input flow information indicative of the input flow through an associated input line of the at least two separate input lines and at least one of the pressure regulating systems is configured to provide input pressure information indicative of the pressure at the associated input line; and a control system for controlling the supply of water from the at least two separate water input lines into the sector of the water supply network, wherein the control system is configured to: receive the input flow information; receive the input pressure information; receive sector pressure information indicative of at least one pressure value determined by at least one pressure sensor within the sector of the water supply network; and generate at least one control output to control the input pressure by controlling at least a first pressure regulating system at a first of the at least two input lines based on the received input flow information from all input lines and based on the received sector pressure information.

24. The water supply system according to claim 23, wherein at least one of the pressure regulating systems comprises a pump station and/or a pressure regulating valve.

25. The water supply system according to claim 23, wherein at least one of the pressure regulating systems comprises a pressure sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic view showing an example of a water supply system with a control system according to the present disclosure, wherein the pressure regulating systems at the input lines comprise one or more pumps;

(3) FIG. 2 is a schematic view showing an example of a water supply system with a control system according to the present disclosure, wherein the pressure regulating systems at the input lines comprise one or more pressure reduction valves (PRV);

(4) FIG. 3 is a schematic view showing an example of a water supply system with a first embodiment of the control system according to the present disclosure;

(5) FIG. 4 is a schematic view showing an example of a control logic of a first embodiment of the control system according to the present disclosure;

(6) FIG. 5 is a view showing diagrams of input flows, input pressures and sector pressures over time in a water supply system with a first embodiment of the control system according to the present disclosure;

(7) FIG. 6 is a schematic view showing an example of a water supply system with a second embodiment of the control system according to the present disclosure;

(8) FIG. 7 is a schematic view showing an example of a control logic of a second embodiment of the control system according to the present disclosure;

(9) FIG. 8 is a schematic view showing an example of an optimisation logic of a second embodiment of the control system according to the present disclosure;

(10) FIG. 9 is a schematic view showing an example of a simplified optimisation logic of a second embodiment of the control system according to the present disclosure; and

(11) FIG. 10 is a view showing diagrams of input flows, input pressures and sector pressures over time in a water supply system with a second embodiment of the control system according to the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(12) FIG. 1 shows a sector 1 of a water supply system with three input lines 3i-k. The sector 1 may be an agglomeration of consumers 5, e.g. a quarter of a town. There are sector pressure sensors 7m,n located within the sector 1 for providing sector pressure information. The sector pressure sensors 7m,n are positioned at critical points within the sector 1 where a local and/or global minimum of pressure is expected. Such critical points may be points of high elevation or large distance from the input lines 3i-k. The sector pressure sensors 7m,n may be referred to as “critical pressure sensors”, because they may indicate if the pressure in the sector 1 is too low. Anywhere else in the sector 1, the pressure should be higher than at the sector pressure sensors 7m,n.

(13) At each of the three input lines 3i-k, there is an input pressure sensor 9i-k and an input flow meter 11i-k provided downstream of a pressure regulating system 13i-k. In FIG. 1, the pressure regulating systems 13i-k are pump stations or pumps. In FIG. 2, the pressure regulating systems 13i-k are PRV stations or PRVs. As the input flow meters 11i-k are quite expensive, it may be beneficial to do without flow meters 11i-k and retrieve flow information from a flow indicator given by the pump(s), for instance, power consumed or current drawn by the pump(s) in a pump-based pressure regulating system, or by the PRV(s), for instance, Δp or opening degree of the PRV(s) in a valve-based pressure regulating system. A control system 15 is configured to receive input flow information indicative of the water input flow through each of the input lines, input pressure information indicative of the input pressure in the associated input lines, and sector pressure information indicative of the pressure values determined by the sector pressure sensors 7m,n. The control system 15 may be one or more processors and memory locally installed at one or more of the pressure regulating system 13i-k and/or on a remote computer system or a cloud-based system. The control system 15 may be signal connected wirelessly or by wires with the sector pressure sensors 7m,n, the input pressure sensors 9i,j, and the flow meters 11i-k. The control system 15 receives the flow and pressure information via signal connections 17i-k,m. The control system 15 is further signal connected wirelessly or by wires with the pressure regulating systems 13i-k via signal connections 19i-k to control the input flow through the associated input line and/or input pressure at the associated input line. The signal connections 17 i-k,m, 19i-k may be part of a data network. The pressure regulating systems 13i-k in form pumps (FIG. 1) may be speed-controlled. The pressure regulating systems 13i-k, in the form of PRVs (FIG. 2), may be controlled in terms of valve opening degree. Optionally, the pressure regulating systems could be a combination of pump(s) and PRV(s). Optionally, the pressure regulating system of one input line could comprise pump(s) and another input line could comprise PRV(s).

(14) FIGS. 3 to 5 refer to a first embodiment of the control system 15 that is configured to apply a pressure-flow control logic. According to this pressure-flow control logic, a first input line 3i of the input lines 3i-k is pressure controlled, whereas the other input lines 3j,k are flow controlled (only 3j is shown in FIG. 4 for simplicity). It is beneficial in view of control stability, but not essential, that the first input line 3i is the input line that is designated to contribute the highest input flow into the sector 1. The pressure-flow control logic does not require an overarching sector control module, so that the control system 15 may be comprised of local input control modules 21i-k at the associated input lines 3i-k. The local input control modules 21i-k may be installed as identical hardware (comprised of one or more processors and memory) and/or software and may be switched to either pressure control mode or flow control mode. The first input control module 21i at the first input line 3i is switched to pressure control mode, whereas the other input control modules 21j,k are switched to flow control mode. The input control modules 21i-k communicate with each other directly via a wireless or wired communication line 22 in order to exchange input flow information. The input flow information is here exchanged in form of a Kalman filter state vector comprising input flows through each of the input lines 3i-k and an expected trend in the total flow of all input lines. The Kalman filter state vector X for three input lines may for instance be updated in each local input control modules as follows:

(15) $X\left(t+\delta t\right)={\left[\begin{array}{c}\begin{array}{c}\begin{array}{c}{q}_i\\ q_j\end{array}\\ q_k\end{array}\\ \delta Q\end{array}\right]}_{t+\delta t}=\left[\begin{array}{cccc}1& 0& 0& \delta t.Math.w_i\\ 0& 1& 0& \delta t.Math.w_j\\ 0& 0& 1& \delta t.Math.w_k\\ 0& 0& 0& 1\end{array}\right].Math.{\left[\begin{array}{c}{q}_i\\ q_j\\ q_k\\ \delta Q\end{array}\right]}_t$
The Kalman filter state vector X is thus recursively updated every δt. The individual input flows are denoted by q.sub.i-k and δQ denotes the change of the total input flow of all three input lines. The contribution of the input flow through each of the input lines to the total input flow Q is thereby controlled according to an associated weight factor w.sub.i-k for each of the input lines to obtain a desired mix of input flows. The total flow Q can be extracted from the Kalman filter state vector X by multiplying an output sum matrix C.sub.sum, e.g. C.sub.sum=[1 1 1 0]. The recursively filtered version of the individual pump flows may be extracted from the Kalman filter state vector X by using an output matrix C.sub.i, i.e. C.sub.i=[1 0 0 0], C.sub.j=[0 1 0 0], and C.sub.k=[0 0 1 0], by applying the equations q.sub.i=C.sub.iX, q.sub.j=C.sub.jX and q.sub.k=C.sub.kX.

(16) The Kalman filter state vector X provides for a linear short-term prediction to bridge the time period lapsed since the latest successful receiving of input flow information from the other input lines. If said time period is long, e.g. several days due to a network breakdown, the first input control module 21i is configured to control the input pressure by controlling the first pressure regulating system 13i at the first input line 3i based on a long-term prediction. The long-term prediction may be based on applying a Fourier transformation on the input flow information from all input lines and recursively updating a truncated Fourier Series for approximating an expected periodic long-term behaviour as follows:
Q(t)=γ[1]+Σ.sub.l=1.sup.L(γ[2l] cos(lωt)+γ[2l+1] sin(lωt)),
wherein γ is a Fourier Series constant being updated based on previous measurements of the total flow Q. The period T=2π/ω of the Fourier Series may be expected to be one day, because the flow demand can often be expected to repeat in a daily pattern.

(17) FIG. 4 shows schematically how the input control modules 21i-k operate according to the first embodiment. The first input control module 21i is switched to pressure-control mode at a switch 23 (downward in FIG. 4), whereas the other input control modules 21j,k are switched to flow-control mode at the switch 23 (upward in FIG. 4). The first input control module 21i receives the input flow q.sub.i through the first input line 3i via signal connection 17i from the associated input flow meter 11i, the local input pressure p.sub.i at the first input line 3i via signal connection 17i from the associated input pressure sensor 9i and critical sector pressure measurements p.sub.cri,m,n via signal connection 17m from the sector pressure sensors 7m,n. The first input control module 21i also receives via direct communication line 22 the Kalman filter state vector X from the other input control modules 21j,k, updates it according to a short-term prediction (STP) and communicates the updated Kalman filter state vector X.sub.i back to the other input control modules 21j,k via direct communication line 22. The updated Kalman filter state vector X.sub.i is not used by the first input control module 21i to control the flow contribution. This is done at the other input control modules 21j,k that are switched to flow-control. The flow-control input control modules 21j,k may switch between the short-term prediction (STP) and a long-term prediction (LTP) based on an evaluation of the time D lapsed since the last successful receiving of a Kalman filter state vector X from the other input control modules 21j,k via direct communication line 22. Based on the weight factor for the associated input line 3j,k, a flow q.sub.set,j,k to be set is extracted from the updated Kalman filter state vector X.sub.j,k by the input control module 21j,k as explained above and communicated to the associated pressure regulating system 13j,k via communication line 19i-k in order to establish the flow q.sub.set,j,k to be set through the input line 3j,k.

(18) In contrast to that, the first input control module 21i performs a curve-controlled update of the pressure p.sub.i at the first input line 3i. The curve-control (CC) may for instance be a quadratic pressure curve such as:
p.sub.set=Aw.sup.2Q.sup.2+B+r,
wherein p.sub.set,i is the input pressure to be set at the first input line 3i, A and B are curve parameters, Q is the total flow through all input lines, w.sub.i is a weight factor for the contribution of the first input flow to the total input flow Q, and r is the minimum pressure to be ensured at the critical sector pressure sensors.

(19) The first input control module 21i applies an algorithm for finding the parameter set [A, B] based on the deviation between the critical sector pressure measurement(s) and the required minimum sector pressure r. The deviation between the required minimum sector pressure r and the critical point measurements may be considered during the time interval [t+δt, t+hδt] with samples {t+δt, t+2δt, . . . , t+hδt}, wherein h is the number of samples on the interval and δt is the sample time in the interval T. A deviation vector ∈.sub.T may be given by

(20) ${ϵ}_T=\left[\begin{array}{c}\min \left\{r-p_{\mathrm{cri},m}\left[t+\delta t\right],.Math.,r-p_{\mathrm{cri},n}\left[t+\delta t\right]\right\}\\ \min \left\{r-p_{\mathrm{cri},m}\left[t+2\delta t\right],.Math.,r-p_{\mathrm{cri},n}\left[t+2\delta t\right]\right\}\\ .Math.\\ \min \left\{r-p_{\mathrm{cri},m}\left[t+h\delta t\right],.Math.,r-p_{\mathrm{cri},n}\left[t+h\delta t\right]\right\}\end{array}\right],$
wherein p.sub.cri,n[t] is the critical sector pressure at time t at the n-th critical sector pressure sensor 7n. Please note that the required minimum sector pressure r can vary with time and might be different for the different sector pressure sensors 7m,n. The minimum function (MIN) is used to ensure that a minimum pressure r always prevails at the most critical, i.e. lowest, of all sector pressure measurements p.sub.cri,m,n. The parameter set [A, B] are estimated in a parameter estimation (PE) in such a way that the deviation of the sector pressure p.sub.cri,m at the most critical of all sector pressure sensors 7m,n from the required minimum sector pressure r is gradually and/or in steps becoming zero or minimal. The pressure p.sub.set,i to be set is communicated to the associated pressure regulating system 13i via communication line 19i in order to establish the pressure p.sub.set,i to be set at the input line 3i. The desired flow mix is achieved by the other input control modules 21j,k configured to flow-control the contribution of the other input lines 3j,k according to weight factors w.sub.i and w.sub.k.

(21) FIG. 5 illustrates the result of the control method applied by the control system according to the first embodiment over eight days of operation. The upper plot shows the individual flows q.sub.i-k, wherein the flows q.sub.i and q.sub.k are shown on top of each other. The middle plot shows the individual input pressures p.sub.i-k (the highest input pressure p.sub.i is outside the visible range during the first two days) and the lower plot shows two critical sector pressure measurements p.sub.cri,m,n. The pressure-control starts after two days during which data were collected to be able to provide both short-term prediction and long-term prediction. In particular, the long-term prediction benefits from a data collection over at least two days. The desired flow mix of 50% from the first input line 3i, i.e. w.sub.i=0.5, and 25% from each of the other input line 3j,k, i.e. w.sub.j,k=0.25, is established by the local flow controllers 21j,k at the input lines 3j,k. The flow mix is essentially unaffected by the local pressure controller 21i starting after two days to control the input pressure p.sub.i at the first input line 3i in such way that the most critical, i.e. the lowest, of the critical sector pressure measurements p.sub.cri,m,n is at or close to the required minimum sector pressure r. As can be seen from the middle plot, the input pressures are significantly reduced once the pressure-control is started. Consequently, the sector pressures p.sub.cri,m,n are reduced to a required minimum sector pressure r and, most importantly, they fluctuate much less since the pressure-control of the first input line 3i was started after two days. This saves energy and reduces leakage in the water supply system. In order to test the control stability, the pressure control was switched after five and a half days to the second input control module 21 while the first input control module 21i was switched to flow control. This switch is hardly visible, which shows that the control method is stable. The fluctuations slightly increase due to fact the second input line 3j is not the largest contributor to the total flow, but the control method is still stable enough for a reliable operation. This flexibility improves the system reliability.

(22) FIGS. 6 to 10 refer to a second embodiment of the control system 15 that is configured to apply a pressure-only control logic. It should be noted that FIG. 6 only shows two of three input lines 3i-k for simplicity. The not shown third input line 3k is analogous to the first and second input line 3i,j. According to the pressure-only control logic, all of the input lines 3i-k are pressure-controlled. The second embodiment is thus more symmetric than the first embodiment having only one pressure-controlled input line. In the second embodiment, the input control modules 21i-k do not communicate directly via communication line 22 with each other, but via a sector control module 25 that may be referred to as “global”, “overarching” or “sector-wide”. The sector control module 25 serves as a communication hub between the local input control modules 21i-k and performs a sector-wide optimisation by updating and providing q,p-curve parameter sets [A.sub.i, B.sub.i] for each input line i. The overarching sector control module 25 may be implemented in a cloud, a network-connected remote computer system or integrated in one or more of the local input control modules 21i-k.

(23) As shown in FIG. 6, the sector control module 25 receives the sector pressure information from the at least one critical sector pressure sensor 7m via signal connection 17m. The local input control modules 21i-k at the input lines 3i-k receive the input pressure information and input flow information from the local input pressure sensors 9i-k and local flow meters 11i-k, respectively, via signal connections 17i-k. Each of the local input control modules 21i-k further receives from the sector control module 25 a parameter set [A.sub.i-k, B.sub.i-k] for the curve-control to be applied at the associated input line 3i-k and a Kalman filter state vector with information about input flows through each of the input lines 3i-k and an expected trend in the total flow Q of all input lines 3i-k. The local input control modules 21i-k controls the associated pressure regulating system 13i-k via signal connection 19i-k to establish an input pressure p.sub.set,i-k to be set at input line 3i-k. The sector control module 25 optimises the parameter set [A.sub.i-k, B.sub.i-k] in such way that the lowest of the critical sector pressure measurements is lowered gradually and/or stepwise to reduce a deviation from the required minimum sector pressure r.

(24) As shown in FIG. 7, the local input control modules 21i-k curve-control (CC) the input pressures at the associated input line 3i-k based on the optimised parameter set [A.sub.i-k, B.sub.i-k] received from the sector control module 25. The curve-control may for instance be a quadratic pressure curve such as:
p.sub.set,i=A.sub.iw.sub.i.sup.2Q.sup.2+B.sub.i+r,
wherein p.sub.set,l is the pressure to be set at the i-th input line 3i, A.sub.i and B.sub.i are curve parameters, Q is the total flow through all input lines, w.sub.i is a weight factor for the contribution of the input flow through the i-th input line 3i to the total input flow Q, and r the minimum pressure to be ensured at the most critical sector pressure sensor 7m.

(25) The local input control modules 21i-k use the received Kalman filter state vector X from all other local input control modules 21i-k to make 5s a short-term prediction (STP) or a long-term prediction (LTP), respectively, for the pressure to be set at the associated input line 3i-k. The choice between either applying the short-term prediction (STP) or long-term prediction (LTP) depends on whether the time period (D) lapsed since the latest successful receiving of input flow information (X) from all input lines was short or long. The local input control modules 21i-k may use the short-term prediction (STP) or long-term prediction (LTP) to perform the curve-control (CC) for bridging times of no communication. At one or more of the subsequent opportunities to communicate with the sector control module 25 again, the local input control modules 21i-k send to the sector control module 25 a Kalman filter state vector X.sub.i-k that is updated with respect to the associated input line 3i-k.

(26) FIG. 8 illustrates the parameter estimation (PE) performed by the sector control module 25 in the second embodiment. The sector control module 25 applies an algorithm for finding the parameter set [A.sub.i, B.sub.i] based on the deviation between the critical sector pressure measurements and the required minimum sector pressure r, and all received Kalman filter state vectors X.sub.i-k that are updated with respect to the associated input lines 3i-k. The deviation between the required minimum sector pressure r and the critical point measurements may be considered during the time interval [t+δt, t+hδt] with samples {t+δt, t+2δt, . . . , t+hδt}, wherein h is the number of samples on the interval and St is the sample time in the interval T. A deviation vector ∈.sub.T may be given by

(27) ${ϵ}_T=\left[\begin{array}{c}\min \left\{r-p_{\mathrm{cri},m}\left[t+\delta t\right],.Math.,r-p_{\mathrm{cri},n}\left[t+\delta t\right]\right\}\\ \min \left\{r-p_{\mathrm{cri},m}\left[t+2\delta t\right],.Math.,r-p_{\mathrm{cri},n}\left[t+2\delta t\right]\right\}\\ .Math.\\ \min \left\{r-p_{\mathrm{cri},m}\left[t+h\delta t\right],.Math.,r-p_{\mathrm{cri},n}\left[t+h\delta t\right]\right\}\end{array}\right],$
wherein p.sub.cri,m[t] is the critical sector pressure at time t at the m-th critical sector pressure sensor 7m. Please note that the required minimum sector pressure r can vary with time and might be different for the different sector pressure sensors 7m,n. The minimum function is used to ensure that a minimum pressure r always prevails at the most critical of all sector pressure sensors 7m,n.

(28) In order to achieve both a minimum critical sector pressure and a desired flow mix, the sector control module 25 may use a parameter vector Θ.sub.T containing the parameters A.sub.i-k and B.sub.i-k from all the individual input lines 3i-k

(29) ${\Theta }_T=\left[\begin{array}{c}{A}_i\\ B_i\\ .Math.\\ A_k\\ B_k\end{array}\right],$
where A.sub.i and B.sub.i are the parameters used for the curve control of the i-th input line 3. A data matrix Σ may be defined by

(30) $\Sigma \left(t\right)=\left[\begin{array}{cccccc}{w}_i^2{Q}^2\left(t\right)& 1& .Math.& .Math.& 0& 0\\ .Math.& .Math.& \ddots & \ddots & .Math.& .Math.\\ 0& 0& .Math.& .Math.& w_k^2{Q}^2\left(t\right)& 1\end{array}\right],$
wherein the matrix Σ gives the relation between the pressure to be set at the individual input lines 3i-k and the parameter vector Θ.sub.T, i.e. p.sub.set(t)=Σ(t)Θ.sub.T, wherein p.sub.set(t)=[p.sub.set,i(t) . . . p.sub.set,k(t)].sup.T is the pressure vector to be set at time t in the period T. The parameter vector Θ.sub.T may be updated using the following recursive update law
θ.sub.T+1=θ.sub.T+K(∈.sub.T.Math.M+λΣ.sub.n=1.sup.N(g(q.sub.n,T,Q.sub.T)−w.sub.n).Math.U.sub.n),
wherein .Math. is the Kronecker product, K, M, and U.sub.n are update gain matrices, and λ>0 is a pre-determined and/or settable balance factor for balancing the importance between the minimal critical sector pressure and the flow distribution. The vector Θ.sub.T denotes the parameters that were used in the time interval [t+δt; t+hδt], and Θ.sub.T+1 denotes the parameters that will be used in the coming period [t+(h+1)δt; t+2hδt]. The terms w.sub.1 to w.sub.N are the weight factors for the required flow mix of all N input lines. The terms ∈.sub.T, q.sub.i,T, and Q.sub.T are vectors with measurements from the time interval [t+δt; t+hδt]. The function g: R.sup.h×R.sup.h.fwdarw.R.sup.h is a vector function given by

(31) $g\left(x,y\right)=\left[\begin{array}{c}\frac{x\left[t+\delta t\right]}{y\left[t+\delta t\right]}\\ \frac{x\left[t+2\delta t\right]}{y\left[t+2\delta t\right]}\\ .Math.\\ \frac{x\left[t+h\delta t\right]}{y\left[t+h\delta t\right]}\end{array}\right].$

(32) In the case of a quadratic p,q-curve as described above, the gain matrix K is given by

(33) $K={\kappa \left(X^{T}X\right)}^{-1}{X}^T,X=\left[\begin{array}{c}\Sigma \left[t+\delta t\right]\\ .Math.\\ \Sigma \left[t+h\delta t\right]\end{array}\right],$
wherein, κ is an update gain factor larger that zero. A good choice for M∈R.sup.n may be

(34) $M=\left[\begin{array}{c}1\\ .Math.\\ 1\end{array}\right].$
For U.sub.i∈R.sup.n, a good choice may be

(35) $U_i=\left[\begin{array}{c}-\frac{1}{N-1}\\ .Math.\\ 1\\ -\frac{1}{N-1}\\ .Math.\\ -\frac{1}{N-1}\end{array}\right],$
wherein the i-th element is 1, whereas the remaining elements equal

(36) 0$-\frac{1}{N-1}.$

(37) FIG. 9 shows a simplified version of the optimisation algorithm applied by the sector control module 25 if the flow mix is considered irrelevant so that the update of the parameter sets [A.sub.i, B.sub.i] is only based on the deviation between the critical sector pressure measurements and the required minimum sector pressure r.

(38) FIG. 10 illustrates the result of the pressure-only control method applied by the control system according to the second embodiment over ten days of operation. Analogous to FIG. 5, the upper plot shows the individual flows q.sub.i-k, wherein the flows q.sub.i and q.sub.k are so similar that they lie on top of each other. The middle plot shows the individual input pressures p-k and the lower plot shows two critical sector pressure measurements. The pressure-control starts after two days during which data were collected to be able to provide both short-term prediction and long-term prediction. In particular, the long-term prediction benefits from a data collection over at least two days.

(39) During the first day, the flows q.sub.i, q.sub.j and q.sub.k are about the same, the input pressures p.sub.i, p.sub.j and p.sub.k are each controlled to be constant. This results in a fluctuation of the sector pressures p.sub.cri,m,n measured at the critical sector pressure sensors 7m,n due to changes in demand for water supply over the day. The input pressures p.sub.i, p.sub.j and p.sub.k are chosen so high in a conservative fashion to ensure that the pressure at the critical sector pressure sensors 7m,n is always above the required minimum sector pressure r.

(40) Energy is wasted for providing the high input pressures and leakage is relatively high due to the high input pressures. The first day thus shows the undesirable situation before the water supply control method described herein is applied.

(41) In the example shown in FIG. 10, there is a desired flow mix of 50% from the first input line 3i, i.e. w.sub.i=0.5, and 25% from each of the other input line 3j,k, i.e. w.sub.j,k=0.25. During the second day, the flow q.sub.i through the first input line 3i is slightly increased compared to the flows q.sub.j,k through the other input lines 3j,k. All input pressures p.sub.i, p.sub.j and p.sub.k are reduced compared to the first day, but still constant over the day. Therefore, the fluctuations of the sector pressures p.sub.cri,m,n measured at the critical sector pressure sensors 7m,n still occur due to changes in demand for water supply over the day. Energy is wasted for providing too high input pressures and leakage is relatively high due to the high input pressures. The second day still shows the undesirable situation before the water supply control method described herein is actually applied.

(42) As can be seen from the middle plot of FIG. 10, the water supply control method described herein is actually started after two days. The input pressures p.sub.i, p.sub.j and p.sub.k are not constant anymore, but controlled to reduce the fluctuations of the most critical, i.e. lowest, of the sector pressure measurements p.sub.cri,m,n. In fact, both sector pressure measurements p.sub.cri,m,n are effectively flattened, because they are highly correlated. It would in principle be possible to reduce the input pressures p.sub.i, p.sub.j and p.sub.k in one step to a level such that the lowest sector pressure measurements p.sub.cri,m is at the required minimum sector pressure r right away. However, in order to minimise the effect on the consumer experience, the input pressures p.sub.i, p.sub.j and p.sub.k are reduced in steps and/or gradually over ten days. Likewise, the desired flow mix is gradually and/or in steps approached over the ten days. As can be seen, an optimised water supply is reached after ten days. The most critical, i.e. lowest, of the sector pressure measurements p.sub.cri,m is constant and at the required minimum sector pressure r to ensuring an minimal pressure within the sector at all times. The desired flow mix is also established. The input pressures p.sub.i, p.sub.j and p.sub.k are optimised to their minimum in order to save energy and reduce leakage.

(43) Where, in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional, preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

(44) The above embodiments are to be understood as illustrative examples of the disclosure. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. While at least one exemplary embodiment has been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter described herein, and this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

(45) In addition, “comprising” does not exclude other elements or steps, and “a” or “one” does not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above. Method steps may be applied in any order or in parallel or may constitute a part or a more detailed version of another method step.

(46) It should be understood that there should be embodied within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of the contribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents.

(47) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

LIST OF REFERENCE NUMERALS

(48) 1 sector of a water supply system 3i-k input lines 5 consumer 7m,n sector pressure sensors 9i-k input pressure sensors 11i-k input flow meters 13i-k pressure regulating systems 15 control system 17i-k,m signal connections 19i-k signal connections 21i-k input control modules 22 communication line 23 switch 25 sector control module r required minimum sector pressure p.sub.i input pressure at input line i q.sub.i input flow through input line i Q total input flow through all input lines w.sub.i weight factor for the flow contribution of input line I to the total flow Q