WO2015033269A1

WO2015033269A1 - A control system for operation of irrigation canals

Info

Publication number: WO2015033269A1
Application number: PCT/IB2014/064211
Authority: WO
Inventors: Mohan Kumar; Mekapati Srinivas; Nareshkumar NANDOLA; Vasudeva Kumar MANTRAVADI
Original assignee: Abb Technology Ltd.
Priority date: 2013-09-03
Filing date: 2014-09-03
Publication date: 2015-03-12

Abstract

The present invention relates to a control system for operation of an irrigation canal to meet water demand and power demand. The control system comprises a plant database, a forecast model, an advanced process control solution provided with plurality of process models and optimizer, operated along with a local controller that receives set points from the advanced process controller. The control system has a plant measurement system along with a plant database to provide values of water flow rate, water level, gate opening, pump speed, location of the hydrokinetic turbines in the irrigation canal, and power generated by the hydrokinetic turbines. The forecast model provides a demand profile corresponding to the water demand and the power demand. The control system generates water level and water flow profiles over a time horizon based on models of the plurality of canal components, the values from the plant measurement system and the plant database considering the time delays associated with the canal components. The optimizer provides set points to control the speeds of the plurality of pumps and openings of the plurality of gates to optimally meet the power and water demand according to the generated water level and water flow profiles.

Description

A CONTROL SYSTEM FOR OPERATION OF IRRIGATION CANALS

FIELD OF THE INVENTION

[001] The invention relates to operation of an irrigation canal, and more particularly to a control system for operation of the irrigation canal to meet water demand and power demand.

BACKGROUND OF THE INVENTION

[002] Irrigation canals are artificial systems developed for transporting water from main water reservoirs to several end users including agricultural farms, industries, factories, and villages. Generally, the irrigation canals are spread over long distances ranging from hundreds of meters to hundreds of kilometers. The irrigation canals comprises sub-canals catering to the water demand of the several end users along the length of the irrigation canal. The water flow to the end users is controlled by modifying the openings of the gates situated in the sub-canals. Moreover, pumps are situated along the length of the irrigation canal to manipulate the water flow by modifying the pump speed.

[003] In general, meeting the demand of end users by optimal operation of different gates and pumps, by satisfying the constraints on water level/flow in the canals should be the key objective. Further, irrigation canals have a potential of producing green energy. The natural flow of rushing water in irrigation canals can be used to produce lOOkW to 2MW of electricity by placing one or more hydro -turbines in the canal. Hence, a minimum flow in the canals has to be ensured to produce electricity.

[004] In some of the current irrigation systems, the irrigation canals are operated in a manual mode or through a local control of the gate openings and control of pump speeds. However, the local control fails to consider uncertainties in the water demand of the end users. Moreover, the local control does not take into account variations in climatic conditions, demand priorities of the end users, and delays associated with the operation of the irrigation canal. Further, for optimal control of the irrigation systems it is essential to consider the operational constraints and design constraints of the irrigation canal.

[005] Therefore, there is a need for a control system that will meet the water and power demand of end users by optimal operation of gates and pumps.

A BRIEF DESCRIPTION OF THE INVENTION

[006] The brief description is provided to introduce concepts related to a control system for operation of an irrigation canal to meet water demand and power demand and the concepts are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

[007] In one aspect, the invention discloses a control system for operation of an irrigation canal to meet water demand and power demand. The irrigation canal comprises plurality of canal components including a plurality of gates situated in main and sub-canals of the irrigation canal, pumping stations having plurality of pumps situated in the irrigation canal, and turbines situated in the irrigation canal for power generation. The power and water supply demand is catered by optimally controlling flow of water in the main and sub-canals such that both power and water supply are maximized with respect to the demand of each of the end users. The control system comprises a plant measurement system along with a plant database for providing values of water flow rate, water level, gate opening, pump speed, location of the hydrokinetic turbines in the irrigation canal, and power generated by the hydrokinetic turbines in the irrigation canals.

[008] The control system also has a forecast model for providing a demand profile corresponding to a water and power demand for a pre-defined time period. The demand profile is provided based on availability of water, predicted inflow of water, seasonal changes, climatic conditions and priorities provided by end users.

[009] The control system uses an advanced process controller with one or more process models and comprising an optimizer for providing set points for control of speeds of the plurality of pumps situated in the irrigation canal and openings of plurality of gates in the irrigation canal. The optimizer provides the set points by solving at least one objective function within the constraints related to the irrigation canal. The constraints related to the irrigation canal can be constraints on water flow in the irrigation canal, the water level in the irrigation canal, the pump speed, and the gate opening.

[010] The advanced process controller using one or more process models and the optimizer provides a set point to local controllers to control speeds of the plurality of pumps and openings of plurality of gates to optimally meet the water and power demands based on demand profile, and water level and water flow profiles generated by the advanced process controller using the one or more process models along with the values provided by the plant measurement system and the plant database and considering the time delays associated with the canal components.. The control system minimizes error between the demand and supply by manipulating speeds of plurality of pumps and openings of plurality of gates in the irrigation system. In one embodiment, the local controller receives set points from the optimizer over a wireless communication means.

[011] The one or more process models used in the control system includes a model for time delays associated with the plurality of canal components during the operation of the irrigation canal and includes process models for canal reach, canal junction, and a weir. The one or more process models can also be used for providing optimal location of hydrokinetic turbine in the irrigation canal along with an upstream model. In an embodiment of the invention, a hydrokinetic turbines are used as these turbines convert kinetic energy of the water flow in the irrigation canal to electrical energy to meet the power demand.

BRIEF DESCRIPTION OF THE DRAWINGS

[012] The detailed description is provided with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer like/similar features and components.

[013] Figure 1 illustrates a control system for operation of an irrigation canal to meet water demand and power demand in an embodiment of the invention.

[014] Figure 2 illustrates an irrigation canal comprising gates for a main canal and sub-canals, pumps, and hydrokinetic turbines situated in the main canal.

DETAILED DESCRIPTION OF THE INVENTION

[015] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration of specific embodiments, which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense.

[016] The present invention relates to a control system for operation of an irrigation canal to meet water demand and power demand. The irrigation canal comprises a plurality of canal components. The plurality of canal components comprises a plurality of gates for opening of a main canal and a sub-canal, and pumping stations having plurality of pumps situated in the main canal. The irrigation canal also comprises hydrokinetic turbines situated in the main/sub canals. The plurality of canal components further is said to comprise aspects that are used for process modeling such as a canal reach, a canal junction, and a weir. The canal reach is a straight length of canal with constant cross-section and slope. The canal junction is a point where two or more canal reaches combine into one or diverge into more canal reaches. The weir is a barrier build across the irrigation canal to alter characteristics of the water flow in the irrigation canal. The weir installed across the irrigation canal causes water to pool behind the structure and allows the water to flow over the top.

[017] The control system for the operation of the irrigation canal described above receives real time values of controlled variables and manipulated variables corresponding to the operation of the irrigation canal. The controlled variables comprises water level, water flow rate, location of hydrokinetic turbines in the irrigation canal, and power generated by the hydrokinetic turbines. The manipulated variables comprises gate opening and pump speed. The control system further models a demand profile corresponding to the water demand and power demand for a predefined time period. In addition, the control system generates a water level profile and water flow profile over a time horizon based on models of the plurality of canal components, and the real time values of the controlled variables. The control system also takes into account time delays associated with the plurality of canal components during the operation of the irrigation canal in order to generate the water level profile and water flow profile. Further, the control system provides set points for the manipulated variables based on the demand profile, the water flow profile, and the water level profile to meet the water demand and the power demand.

[018] The control system for the operation of the irrigation canal is described in detail with reference to figure 1. The figure 1 illustrates the control system 100 for the operation of the irrigation canal to meet the water demand and the power demand. In one embodiment of the invention, the control system 100 comprises a plant database 102, a forecast model 104, a control scheme 105 implemented through local controllers and an advanced process control scheme comprising process models 106, and an optimizer 108. The control system platform may be a supervisory control and data acquisition (SCADA), a distributed control system (DCS), a programmable logic controller (PLC), or any other control platform.

[019] The plant database 102 has plant parameters eg values of water flow rate, water level, gate opening, pump speed, location of the hydrokinetic turbines in the irrigation canal, and power generated by the hydrokinetic turbines. The plant database is created from the values received (inputs, measured and analyzed) in the control system platform and through different communication systems such as a wired, wireless, or a GPS. The measured values are provided by a plant measurement system.

[020] The forecast model 104 provides a demand profile corresponding to the water demand and the power demand for a pre-defined time period. The forecast model, 104 takes into account the demand profiles, for various end users, over a specified time horizon, which can be dynamic in nature. The forecast model 104 takes into consideration the water demand and the power demand across different locations situated along the length of the irrigation canal. The forecast model 104 also considers different uncertainties related to the demand. The uncertainties may be related to availability of water in the irrigation canal, predicted inflow of water, seasonal changes, and climatic conditions.

[021] The control system 100 receives end user priorities, parameters for optimization and constraints for flows/levels/heads in the canal. The user inputs also includes locations of hydro-turbines along the length of the canal. The control scheme 105 includes the advanced process control, local control, and the process models 106. Advanced process control uses the process model 106 to provide optimal set points for gate openings and pump speeds. The process models 106 generate future water level profile and future water flow profile over a time horizon based on models of the plurality of canal components, the received values, and time delays associated with the canal components during the operation of the irrigation canal. The process model 106 referred is a plurality of process models including that for canal reach, the canal junction, a gate, and a hydrokinetic turbine. The process models 106 is also used to estimate states of processes (or unavailable measurements). The output from the forecast model, 104, serves as a feed forward component to the advanced process control. The local controller receives optimal set points from advanced process control through use of optimizer 108 and accordingly the local controller.

[022] The following paragraphs provide with information on some exemplary process models used by the control system. The process models are for canal reach, canal junction, gates in the irrigation canals, weirs in the irrigation canals, hydro-turbines used in the irrigation canal and also for delays associated with the canal and/or gates.

[023] Canal Reach: A canal reach is a straight length of the irrigation canal with constant cross-section and slope. The flow model for the canal reach assumes one- dimensional unsteady flow. In general, length of the canal reach is significantly large as compared to the width, and hence variations across the cross-section are considered to be negligible. The flow in the canal reach is modeled by Saint Venant's Equations. The Saint Venant's equations are a system of non-linear hyperbolic partial differential equations. In general, the flow is assumed to be one-dimensional and gradually varying. Assuming canal slope is negligible and the fluid is incompressible i.e. constant density, conservation of mass is described by the following continuity equation.

where, A is the area of flow in m², qi is the seepage loss in m²/s, Q is the flow rate in m³/s, and x is the position along the length of the canal.

[025] The rate of change in momentum of the flow is equal to the external forces acting on the system. Therefore,

where, V is the velocity in m/s and Sf is the friction slope which can be calculated using Manning's equation.

[026] Canal Junction: A canal junction may be defined as a point where two or more canal reaches combine into one or diverge into more canal reaches. The junction length is assumed negligible which eliminates the consideration of energy losses. The total flow entering into the canal junction is equal to the flow leaving the canal junction.

(3)

where, Si is the flow coefficient (-1 for upstream and +1 for downstream) and Qi is the flow rate at junction in ith canal reach.

[027] Weir: The plurality of canal components comprises a weir. The weir is a barrier across the irrigation canal designed to alter flow characteristics. In most cases, the weir take the form of a barrier, smaller than most conventional dams. The weir installed across the irrigation canal causes water to pool behind the structure and allows the water to flow over the top. The weir is used to prevent flooding, and measure discharge. The weir may be of several types comprising a broad crested weir and a sharp crested weir. The discharge equation of the weir gives a relation between the flow rate and the head upstream of the weir.

where, Q is the discharge through the weir in m³/s, C is the weir discharge coefficient (varies between 2.6 to 4.2 depending upon the shape), B is the weir width in meters, and H is height of the upstream flow above the weir crest in meters.

[029] Gate: A gate is a flow control structure that regulates the amount of water flowing in a particular canal reach. As the gate affects the flow into or out of the canal reach at the canal junction, the flow in other canal reaches is also affected. The gates are installed at strategic locations in order to control flow in the entire irrigation canal system. The gate blocks the flow when the gate opening is zero and as the gate opening is increased, the gate lets more water to pass through. The gate may be of several types including a sluice gate, and a radial gate. When the submergence of the sluice gate is less than 0.67, the gate is said to be free flowing, and the discharge through the gate is given as follows,

[031] When the submergence is in the range 0.67 to 0.8, the flow is said to be in transition, and the discharge through the gate is given as follows,

[033] Similarly, when the submergence is greater than 0.8, the discharge through the gate is given by the following equation,

Where, Q is flow through the gate in m³/s, C is gate discharge coefficient, W is gate width in meters, B is the gate opening in meters, and H is difference in the heights of the upstream and downstream levels in meters.

[034] Hydrokinetic Turbine: A hydrokinetic turbine situated in the main canal converts the kinetic energy of flowing water into electrical energy. It is different from traditional turbines that convert the potential energy or head of water stored in a dam into electrical energy. The hydrokinetic turbines do not require any additional infrastructure development and therefore can be easily installed in flowing streams. The hydrokinetic turbines may be of several types based on rotor orientation. For example, the hydrokinetic turbines may be an axial hydrokinetic turbine, a cross flow hydrokinetic turbine, and an inclined hydrokinetic turbine. Generally, the power equation is same for all the hydrokinetic turbines. The power equation for the hydrokinetic turbine is represented as, [035] P = ) P D C_pV³ (8)

Where, P is the output power of the hydro turbine in Watts, p is the density of fluid in kg/m³, η is the efficiency, C_p is the coefficient of performance of turbine, and V is the velocity in m/s.

[036] Still referring to the figure 1 , the control system 100 comprises a process model that can describe dynamics of upstream. The integrated process models with upstream models can be used to identify an optimal placement of hydro-turbines along the canal. This can be achieved by solving optimization problem and/or via simulation.

[037] The process model 106 is used to generate the water level profile and the water flow profile based on the received values. The received values comprises the real time values of water flow rate, water level, gate opening, pump speed, location of the hydroelectric turbines in the irrigation canal, and power generated by the hydro-electric turbines. The received values also comprises real time values of pressure measured across the sub-canal. When the real time values are not available, the process model 106 estimates the values of the water flow rate and water level from available values of the water flow rate and water level. The values may be estimated from the available values through any soft sensing technique such as inferential modelling. Further, the real time values and the estimated values are used to update the models of the plurality of canal components.

[038] The process model 106 also takes into account the delays associated with the plurality of canal components during the operation of the irrigation canal. The delay may be present in natural flow of water in the irrigation canal and in the gate opening. The delay may be estimated by taking into consideration the time taken for operation of the gate and effect of the operation of the gate on the flow of the water. The estimated delay may be accounted for by selecting an appropriate time horizon for generating the water level profile and the water flow profile. For example, the time horizon may be at least as long as the highest delay time of the canal reaches. Alternatively, the time horizon may be the sum of the delay times of all the canal reaches.

[039] In another aspect of the invention, the process model 106 is used to estimate optimal location of the hydrokinetic turbines in the irrigation canal. The optimal location of the hydrokinetic turbines is estimated based on a process model and an upstream model. The process model includes the updated model of the canal components. The upstream model represents dynamics of the upstream in the irrigation canal. This aspect is useful as an example in scenarios where the control system is used initially for optimizing water supply to meet the water demand and the canal system is upgraded to also provide for power demand.

[040] Still referring to figure 1, the control system 100 for operation of the irrigation canal further comprises an optimizer 108. The optimizer 108 provides set points for control of pump speed and the gate opening based on the demand profile, the water level profile, and the water flow profile to meet the water demand and the power demand. The control scheme works by comparing received values of the water flow rate, the water level, the power generated by the hydrokinetic turbine with the demand profile and accordingly actuating pump speed and gate opening for optimally meeting water and power demands i.e. in order to minimize gap between the received values and the demand profile, the optimizer 108 provides set points for the pump speed and the gate opening. The pump speed and the gate opening are manipulated by local controllers and actuators situated at the pumping stations and the gates based on the set points provided by the optimizer 108.

[041] The optimizer 108 provides the set points considering the constraints related to the irrigation canal. The constraints related to the irrigation canal comprises constraints on water flow in the irrigation canal, the water level in the irrigation canal, the pump speed, and the gate opening. For example, the pumping station situated in the main canal may have a limited pumping capacity. Moreover, the water flow rate through the gate may be constrained due to presence of sea water and level of the sea water in contact with the sub-canal. Optimization is performed through use of the process models, to find solutions considering the set constraints to maximize both water and power supply as per the priorities/inputs provided by the users of the irrigation system.

[042] The control system 100 for the operation of the irrigation canal may be further explained by referring to figure 2. The figure 2 shows an irrigation canal comprising gates for a main canal and sub-canals, pumps, and hydrokinetic turbines situated in the main canal. The irrigation canal illustrated consists of a reservoir controlled by Gate G. The Gate G supplies water to the main canal. The main canal has three sub-canals to supply water to three different end users/customers. The end customers may include domestic users, agricultural lands, and industries. The water flow to the end customers is controlled by Gates G, Gl, G2 and G3. The main canal has three hydrokinetic turbines (Tl, T2, and T3). The hydrokinetic turbines situated at three different locations make use of the natural flow of water to generate the power. Further, the main canal has pumping stations (PS 1 , PS2 and PS3) at three different locations mainly to transport the water if the flow by gravity is not sufficient.

[043] The operation of the irrigation canal illustrated in the figure 2 may be controlled by the control system 100. The control system 100 comprises a plant measurement system with sensors for making critical measurements, and plant database 102 for storing and providing the measured values for further computations. The critical measurements are of water flow rate (F, Fl, F2, and F3), water level (L, LI, L2, L3, and L4), pump speeds (S I, S2, and S3), pressures (P, PI, P2, and P3), gate openings (H, HI, H2, and H3), and power generated by the hydrokinetic turbines (El, E2, and E3). In case, if some critical measurements are not available, then they are estimated from the available measurements through soft sensing techniques such as inferential modeling. Further, these critical measurements which are either measured or estimated can also be used to update process models, 106 (mathematical models) and to monitor the performance of the canal components. As described previously, the process model accounts for the time delays which can be estimated by several ways, and one such way is through time taken for the gate operation, and its effect on the downstream.

[044] In general, the demand of particular end user/end customer (DF1 or DF2 or DF3) is addressed by manipulating the corresponding gate opening without considering its effect/interaction on other gates. In addition, this practice does not consider the delay of operation in the gates which lead to either over/under supply of water to the end customers. Further, the natural flow of water will also have lot of kinetic energy which can be extracted in the form of power by placing turbines in the canal. However, placing the turbines result in increased interactions among canal components.

[045] The forecast model 104 provides the demand profile corresponding to the water demand (DF1, DF2, DF3) and the power demand (DEI, DE2, DE3) for the end customers, in this exemplary case, situated at the three different locations. The demand profiles obtained through forecast models considers the effect of uncertainties such as seasonal changes, climatic conditions etc.

[046] Further, with use of the process model 106 the water level profile and water flow profile for a time horizon are provided based on the models of the canal components illustrated in the figure 2 for optimal operation of irrigation system with the control system 100.

[047] The control system compares the received values with the water demand and the power demand obtained from the forecast model 106. The control system further minimizes the error between the power demand and the water demand, and supply by providing set points for the pump speeds (SI, S2, S3), and the gate openings (HI, H2, H3), for the exemplary irrigation system. The advanced process control solution also considers operational and design constraints of the irrigation canal while providing the set points. Further, the advanced process control solution avoids over/under supply by accounting time delay in process model. This results in minimization of water wastage while generating green energy using hydro-turbines resulting in improved efficiency of operations. In this example, the optimizer is said to provide set points for optimally meeting water and power demand. The objective of meeting water and power demand can be considered as one single objective or two separate objectives i.e. treating meeting water demand as a first objective and then meeting power demand through use of two separate objective functions. The optimization problem can be solved using well known optimization techniques. The optimal set points provided by the optimizer are communicated to the local controller through the communication means including wireless communication means provided in the control system for the irrigation canal.

[048] This written description uses examples to describe the subject matter herein, including the best mode, and also to enable any person skilled in the art to make and use the subject matter. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

CLAIMS:

1. A control system for operation of an irrigation canal to meet water demand and power demand, wherein the irrigation canal comprises plurality of canal components including a plurality of gates for regulating amount of water flowing in main and sub- canals of the irrigation canal, pumping stations having plurality of pumps situated in the irrigation canal, and hydrokinetic turbines situated in the irrigation canal, the control system comprises:

a plant measurement system along with a plant database for providing values of water flow rate, water level, gate opening, pump speed, location of the hydrokinetic turbines in the irrigation canal, and power generated by the hydrokinetic turbines in the irrigation canals;

a forecast model for providing a demand profile corresponding to a water and power demand for a pre-defined time period;

an advanced process controller using one or more process models and an optimizer for providing set points for control of speeds of the plurality of pumps situated in the irrigation canal and openings of plurality of gates in the irrigation canal; and

wherein, the advanced process controller using one or more process models and the optimizer provides a set point to local controllers to control speeds of the plurality of pumps and openings of plurality of gates to optimally meet the water and power demands based on demand profile, and water level and water flow profiles generated by the advanced process controller using the one or more process models along with the values provided by the plant measurement system and the plant database.

2. The control system of claim 1 , wherein the one or more process models includes a model for time delays associated with the plurality of canal components during the operation of the irrigation canal.

3. The control system of claim 1 , wherein the one or more process models includes model for plurality of canal components including a process models for canal reach, canal junction, and a weir.

4. The control system of claim 1, wherein the demand profile is provided based on availability of water, predicted inflow of water, seasonal changes, climatic conditions and priorities provided by end users.

5. The control system of claim 1, wherein the optimizer provides the set points by solving at least one objective function within the constraints related to the irrigation canal.

6. The control system of claim 5, wherein the constraints related to the irrigation canal comprises constraints on water flow in the irrigation canal, the water level in the irrigation canal, the pump speed, and the gate opening.

7. The control system of claim 1, wherein the one or more process models is used for providing optimal location of hydrokinetic turbine in the irrigation canal along with an upstream model.

8. The control system of claim 1 , wherein the hydrokinetic turbines convert kinetic energy of the water flow in the irrigation canal to electrical energy to meet the power demand.

9. The control system of claim 1, wherein the control system minimizes error between the demand and supply by manipulating speeds of plurality of pumps and openings of plurality of gates in the irrigation system.

10. The control system of claim 1, wherein the local controller receives set points from the optimizer over a wireless communication means.