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Enhancements and Modifications to the Full Equations (FEQ) Model, March 1995 to August 1999
Note: This document is separate from the U.S. Geological Survey report by Franz and Melching (1997). This description of enhancements and modifications to the Full Equations Utilities Model has not been approved by the Director of the U.S. Geological Survey.

Input description update for section 13.12 Operation of Control Structures Block-- Operation Tables, Franz and Melching (1997a), p. 187

Section 13.12 Operation of Control Structures Block--Operation Tables

Purpose: The operation rules for any dynamically operated control structures are given with this block. This block is only required if SOPER=YES in the Run Control Block (section 13.1). The maximum number of Operation-Control Blocks allowed in FEQ is specified in the parameter MNBLK in the INCLUDE file ARSIZE.PRM (appendix 3). This number may be increased as necessary and FEQ recompiled.

Heading: One line of user-selected information. The suggested string is OPERATION OF CONTROL STRUCTURES.

LINE 1
Variable: BLK
Format: 4X, I5
Example: BLK=00001
Explanation:
Gives the number of the operation-control block table. BLK=-1 terminates input of operation blocks. Operation-control block tables must be numbered consecutively from 1.

LINE 2
Variable: BLKTYP, SPEEDS
Format: 8X, A8, 1X, 7X,I5
Example: BLKTYPE=PUMP SPEEDS= 4
Explanation:
Gives the type of the operation-control block and the number of discrete speeds that a multi-speed pump can have. Making the speed range discrete avoids having the pump operate at a physically unrealistic speed during its operation. If the number of speeds is 4, then the pump speeds are: 0.0, 0.25, 0.50, 0.75, 1.00. There are three types of operation blocks: BLKTYPE=PUMP denotes that a one-way pump is being controlled, BLKTYPE=PUMP2WAY denotes that a two-way pump is being controlled, and BLKTYPE=GATE denotes that a gate is being controlled.

LINE 3
Variable: MINDT
Format: 6X, F10.0
Example: MINDT=300.
Explanation:
Gives the minimum time that must elapse between changes to the gate or pump setting. Changes in the setting can only occur at the boundary between time steps but at least MINDT seconds must have elapsed since the last change before the next change can be made.

LINE 4
Variable: PINIT
Format: 6X, F5.0
Example: PINIT=0.62
Explanation:
Initial value for the opening fraction. The opening fraction varies between 0 and 1. When PINIT=0, the gate is completely closed (underflow gates: sluice gates, tainter gates, and so forth), or in the fully raised position (overflow gates: drum gates and related devices). The gate is so positioned to either force the flow to zero or reduce it to a minimum value. When PINIT=1.0 the gate is positioned such that the flow is given its maximum value for the given water-surface elevation. For a pump the values gives the speed of the pump relative to the standard speed chosen for the table defining the relationship between flow and head for the pump. The pump is off when PINIT=0.0 and the pump is on at the relative speed given if PINIT0.

If BLKTYPE=GATE (Gate Operation)

LINE 5
Variable: HEAD
Format: A80
Example: BRAN NODE KEY MODE MNRATE LRATE LOWLIM
HGHLIM HRATE LPRI NPRI HPRI DPDT
Explanation:
User supplied headings for subsequent information.

LINE 6

Variables: BRA, NODE, KEY, MODE, MNRATE, ML, LL, LU,
MU, LPRI, NPRI, HPRI, DPDT
Format: I5, 2A5, I5, 5F7.0, 3I5, F5.0
Explanation:
Specifies the parameters defining a control point used in the operation of a structure. The values are:

BRA is the branch number for the control point. BRA=0 if the node is an exterior node. BRA<0 denotes the end of input for the current block.
NODE is the node label for the control point.

KEY is the ELEV if control point senses water surface elevation, KEY=QCON if control point senses flow rate and the null zone limits are constant values, KEY=QVAR if the control point senses flow rate and the null zone limits are variable, and KEY=new style exterior node label if water-surface elevation difference is being sensed. The null zone is that range of the sensed value (flow, elevation, or elevation difference) in which the setting of the structure will not be changed. If elevation difference is selected the difference is taken in the sense of elevation at node in NODE less the elevation at node in KEY.

MODE=0 means that the structure opening is changed whenever the value being sensed at the control point is outside the null zone. MODE=1 means structure opening is changed only if the value being sensed at the control point is outside the null zone and is not moving in the right direction with sufficient speed.

MNRATE is the minimum change per hour under MODE=1 required to avoid changing the structure opening. For example, if KEY=ELEV indicating that water-surface elevation is being sensed and if MNRATE=0.01 then the elevation at the sensing point must be moving toward the null region at a rate exceeding 0.01 foot/hour to avoid having the structure opening changed.

ML is the rate factor for the rate of change of opening when the control point is below the null zone. This rate factor is a multiplier on the distance that the sensed value is from the closest boundary of the null zone. The resulting rate is the change per hour of the structure opening as measured by an opening fraction,p, which is taken as 0.0 when the structure opening is such as to restrict the flow by the maximum amount and as 1.0 when the structure opening is such to restrict the flow by the minimum possible amount. The actual rate of opening used is limited by DPDT, given later in the input. Note that the rate factor sign is determined by the location of the control structure relative to the control point as well as the goal of the control structure.

LL is the lower limit for the null zone.

LU is the upper limit for the null zone.

MU is the rate factor for the rate of change of opening when the control point is above the null zone.

LPRI is the numerical priority of the action for this control point when the sensed value is below the null zone. Numerical priority 1 is the highest priority, 2 is next, and so forth. The numbers are ordinal only, that is, used only for relative ranking. There is no degree of priority difference so that the only relationship used is the quality of being equal, being greater than, or being less than.

NPRI is the priority of the action for this control point when the sensed value is in the null zone.

HPRI is the priority of the action for this control point when the sensed value is above the null zone.

DPDT is the absolute value of the maximum permitted rate of change in the opening fraction for the structure.

When KEY is the QVAR an additional two lines of input are required. The first line gives headings and the second line the values required to define the variable null zone.

LINE 6a
Variable: HEAD
Format: A80
Example: NUMB NZHW NODE NDWT NODE NDWT NODE NDWT
Explanation:
User supplied headings for subsequent information.

LINE 6b

Variables: NUMB, NZHW, (NDVEC(J), NDWT(J), J=1,NUMB)
Format: I5, F5.0, 7(I5,F5.0))
Explanation:
Specifies the values required to define the variable null zone limits. The meaning of the values is:

NUMB is the number of exterior nodes to use in computing the flow to define the mid-point of the null zone.
NZHW is the null zone half width. The null zone half width is added to the mid-point flow for the null zone to give the upper limit of the null zone. It is subtracted from the mid-point flow to give the lower limit.

NDVEC contains the NUMB exterior nodes used to compute the mid-point of the null zone.

NDWT contains the weight to use for each exterior node's flow in computing the mid-point of the null zone. This weight can be positive or negative. The weight on the exterior node flows can be used to deduct flow which leaves the system by some other route than the structure being operated by this control block. Also the weight can be used to account for other sources of inflow, such as diffuse inflow not reflected by any exterior node. As the heading indicates, the exterior node and its associated weight are given pairwise in the input.
If BLKTYPE=PUMP (Pump Operation)

LINE 5
Variable: HEAD
Format: A80
Example: BRAN NODE KEY MNRATE RISE FALL ONPR OFPR
Explanation:
User supplied headings for subsequent information.

LINE 6

Variables: BRA, NODE, KEY, MNRATE, RISE, FALL,
ONPR, OFPR
Format: I5, 2A5, F7.0, 4I5
Explanation:
Specifies the parameters defining a control point used in the operation of a potentially variable speed pump. The values are:

BRA is the branch number for the control point. BRA=0 if the node is an exterior node. BRA<0 denotes the end of input for the current block.

NODE is label for the node at control point.

KEY is the ELEV if control point senses water surface elevation, and KEY=QCON if control point senses flow rate. The nature of pump control does not permit using a variable width null zone as for gates when KEY=QVAR is specified. The null zone is that range of the sensed value (flow or elevation) in which the setting of the pump will not be changed.

MNRATE is the minimum change per hour in the sensed variable (flow or elevation) required to change the table defining the pump operation. There are two pump operation tables possible: one for a rising level at the control point and one for a falling level. The level must have been moving at least as fast on the average as the rate given in MNRATE before FEQ decides that the level is really rising or falling. This tolerance is made available to prevent rapid switching between the tables.

RISE is the table number giving the pump speed as a function of the sensed variable when the sensed level is increasing in magnitude. This function includes the definition of the null zone for the pump. A discussion of the pump speed function is presentedin section 8.1.2.2.3.2.

FALL is the table number giving the pump speed as a function of the sensed variable when the sensed level is decreasing in magnitude.

ONPR is the priority to assign to the control point action when the pump speed function requests that the pump be turned on.

OFPR is the priority to assign to the control point action when the pump speed function requests that the pump be turned off.
Line 6 is repeated for each control point given for each table. The auxiliary lines, 6a and 6b for KEY=QVAR must also be repeated in sequence. A table is terminated by a negative branch number. Input of tables is terminated by a negative value for BLK.
A dynamically operated structure can have more then one control point and the control points may recommend different actions. Some method must be devised to decide which control point's action should be taken. The method used here is to attach a priority to each of the three possible actions requested by the control point. The highest priority action for all the control points is then the action taken.
The null region is needed to prevent or minimize "hunting" of the structure opening fraction. Thus the action requested when in the null region is no change in the opening fraction. Experience to date has indicated that MODE=1 is the best choice for gates because the response at the control point to the structure opening change can be delayed so that the control point is still out of the null region but is moving in the right direction. If MODE=0 is used the structure opening fraction will increase to its maximum value resulting in a large overshoot of the desired result. This will then be followed by the structure opening decreasing to its minimum possible value with a subsequent overshoot of the desired result. Using MODE=1 and a properly sized null region can eliminate this illogical hunting behavior of the system.
The simple priority method for selecting the action to take ignores the direction of motion of the sensed values. Direction of motion has not been included for gate control but has been included for control of a pump. The number of rules used for the operation of control structures is essentially unlimited. Thus changes will need to be made for specific examples that do not fit the current generalized scheme.
The QVAR option will operate the gate so that the outflow will follow the variable null zone closely if the outflow changes slowly enough. If the null zone changes rapidly, the rules for opening the gate may prevent following the null-zone changes, or the head available may make it impossible to follow null-zone changes. Other rules may of course override the QVAR rule based on the priority of the various control points.

If BLKTYPE=PUMP2WAY (Pump Operation)

A two-way pump is a pump designed such that the water can be moved in either direction. This does not mean that the pump is reversible but that it has extra gates or valves near it that allow the water to flow through the pump in a single direction while directing the water in either direction, depending on the gate setting. Two-way pumps are sometimes used to both irrigate and drain farm land depending on the conditions. This means that the pumps operate with small head differences so that they can be used to move water in two directions.
The following assumptions are made to make implementation simple:
1. The losses in conduits/channels used to connect the pump to the flow system are assumed to be the same for both directions. That is, FEQ assumes that the pump installation is symmetrical with regard to the losses.
2. The pump rating is the same in both directions.
3. The direction given in the Code 5 type 3 instruction for the pump defines the default direction. That is, if the speed of the pump is> 0, then it is pumping in the default direction. If the speed of the pump is< 0, then it pumps opposite to the default direction.
The input for a two-way pump is the same as for a one-way pump. The major changes are in the operation of the pump and not its definition.
A one-way pump is controlled by using function tables that give its speed as a function of the control value: flow or elevation of water surface. LetSPD be the value of speed found from one of these function tables. The following rules govern the speed setting for one-way pumps:
1. IfSPD > 0, then if the pump is off, it is turned on at the given speed,SPD. If the pump is on, its speed is set toSPD.
2. IfSPD = 0, then the speed of the pump is unchanged.
3. IfSPD < 0, then the pump is turned off if it was on and remains off if it was off.
These rules remain the same for one-way pumps. However, control functions like this will no longer suffice for two-way pumps because the rules for speed of the pump must now define the direction of pumping as well. Therefore, the rules for the control tables for two-way pumps have been changed. This means there are now two kinds of control tables for pumps: those for one-way pumps and those for two-way pumps.
In order to control two-way pumps a tolerance value at near zero speed was defined. This value is0.01. No pump will likely operate at0.01 of its maximum speed and therefore this value has been taken as a special value for the control of two-way pumps. This value is calledPUMPEPS and is used in a pump-control table to define pump speed as well as direction.
A pump control table for a two-way pump can have speeds that are negative as well as positive, always limited so that-1 less than or equal to SPD less than or equal to +1. However, we need a value that defines a null zone for both positive and negative speeds. For a one-way pump the null zone is defined bySPD = 0.00 but that is not adequate for two-way pumps because we have no way for turning the pump off and on.
The following rules for the meaning of a value from the pump control table (function) for a two-way pump is as follows:
1. WhenSPD > PUMPEPS the direction is the same as given by the user in the pump instruction. The pump speed is set toSPD.
2. WhenSPD < -PUMPEPS the direction is opposite to that given by the user and the pump speed is the absolute value ofSPD.
3. IfSPD = -PUMPEPS orSPD = +PUMPEPS then the pump direction and speed remains unchanged. This is the null zone value for control of a two-way pump.
4. If-PUMPEPS < SPD < PUMPEPS, that is, ifSPD is within the tolerance interval about zero defined byPUMPEPS, then the pump is turned off.
The format of the information for the two-way pump control block is the same as for a one-way pump control block. However, the function tables used to control the pump will differ in the contents as just outlined here.
Left ArrowBack to Franz and Melching (1997a), p. 191, section 13.12, Operation of Control Structures Block-- Operation Tables, p. 186