Method and system for fluid flow control in a fluid network system

A control system for fluid flow control in a fluid network system having a plurality of fluid machines, the control system comprising:

• a processing system configured to:
• obtain a respective current fluid flow rate associated with each fluid machine via a respective sensor,
• obtain a current fluid machine speed of each fluid machine, the current fluid machine speed being a condition of the respective fluid machine in operation,
• obtain desired fluid flow rates in the fluid network system,
• determine a new fluid machine speed for each fluid machine based on the current fluid machine speed of the respective fluid machine and a change in fluid machine speed of the respective fluid machine required to obtain the desired fluid flow rates, wherein the change in fluid machine speed is determined by minimizing a total fluid machine power by utilizing a total fluid machine power model defined by ΔE=H eΔβ2 where He is a constant matrix and Δβ is a vector containing the change in fluid machine speed for all fluid machines, the minimization being performed with constraints for fluid flow rate, fluid machine differential pressure, and fluid machine speed associated with the respective fluid machine, the fluid machine differential pressure being a differential pressure over the respective fluid machine,
• and
• control the speed of the plurality of fluid machines according to the new fluid machine speeds such that the minimum total fluid machine power in the fluid network system is attained, wherein prior to obtaining the respective current fluid flow rate associated with each fluid machine, the control system is configured to empirically determine the total fluid machine power model by determining a relation between a change in fluid machine speed and a corresponding change in fluid machine power for each of the plurality of fluid machines, wherein the relation forms part of the model, and wherein determining the total fluid power model further comprises determining the constant matrix by changing the fluid machine speed of the plurality of fluid machines by applying input signals to motors of the fluid machines, according to a pattern that allows the fluid flow in the fluid network system to settle to a steady state after the change in fluid machine speed of a given fluid machine of the plurality of fluid machines has been made, and wherein the constant matrix defines a relation between a control parameter related to the change in fluid machine speed and the change in fluid flow obtained by the sensors.