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Can you run a VSP with a Control node and Logical Controls at the sametime?Problem ID#: 79738
VSP Interactions with Simple and Logical ControlsThe VSP model and APEX have been designed to fully integrate with thesimple and rule based control framework within Bentley WaterGEMS V8i .You must keep in mind that the definition of controls requires that thestate (On, Off, Fixed Speed Override) and speed setting of a VSP beproperly managed during the simulation. Therefore, the interactionsbetween VSPs and controls can be rather complex. We have tried to theextent possible to simplify these interactions while maintaining thepower and flexibility to model real world behaviors. The paragraphs thatfollow describe guidelines for defining simple and logical controls withVSPs.Pattern based VSPsThe pattern of relative speed factors specified for a VSP takesprecedence over all simple and logical control commands. Therefore, theuse of controls with pattern based VSPs is not recommended. Rather, thepattern of relative speed factors should be defined such that controlobjectives are implicitly met.VSPs with APEXA VSP can be switched into any one of three different states. When theVSP is On, the APEX will estimate the relative speed sufficient tomaintain a constant pressure head at the control node. When the VSP isOff, the relative speed factor and flow through the pump are set tozero, and the pressure head at the control node is a function of theprevailing network boundary and demand conditions. When the controlstate of a VSP is Fixed Speed Override, the pump will operate at themaximum speed setting and the target head will no longer be maintained.The Temporarily Closed state for a VSP indicates that the check valve(CV) within the pump has closed in response to prevailing hydraulicconditions, and that the target head cannot be maintained. The VSPcontrol node can be specified at any junction node or tank in a networkmodel. As described below, however, the behavior of simple and logicalcontrols depends on the type of control node selected.Junction NodesWhen the VSP control node type selected is a junction node, the VSP willbehave according to some automatic behaviors in addition to the controlsdefined for the pump. If the head at the control node is above thetarget head, the pump state will automatically switch to Off. If thehead at the control node is less then the target head, the pump statewill automatically switch to On. The VSP will automatically switch intoand out of the Fixed Speed Override and Temporarily Closed states inorder to maintain the fixed head at the control node and prevent reverseflow through the pump. Additional controls can be added to model morecomplex use cases.Tanksâ€”When the VSP control node is a tank, you must manage the state ofthe pump through control definitions, allowing for flexible modeling ofthe complex control behaviors that may be desired for tanks. If a VSPhas a state of On, the pump will maintain the current level of the tank.For example, at the beginning of a simulation, if a VSP has status of onit will maintain the initial level of the tank. As the simulationprogresses and the pump happens to turn off, temporarily close, or gointo fixed speed override, the level in the tank will be determined inresponse to the hydraulic conditions prevailing in the network. When theVSP turns on again, it will maintain the current level of the tank, notthe initial level. Thus control statements must be written that dictatewhat state the pump should switch to depending on the level in the tank.A pump station with a VSP and a fixed-speed pump operating in a coordinated fashion can be used to model tank drain and fill operations.