Allocate

- Version Ver. 3.0 - Optimal Unit Allocation Software

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Unit allocation / commitment is the process of deciding when and which generating units at each power station to start-up and shut-down. This process is very complicated when 2 or more generating units are considered due to the fact that the number of combinations increases exponentially with the number of available generating units. To solve this problem in efficient way mathematical model and computer program is required.

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Allocate is a computer program that can be used to very efficiently solve the above problem. Using a mathematical model and specific numerical techniques Allocate provide an optimal or best-fit solution to the unit allocation / commitment problem. The use of the program can result in significant improvements to daily energy production or revenues. Allocate is an optimization program because it is based on mathematical formulation of the unit allocation / commitment problem and provides an optimal solution depending on the selected objective function taking into account numerous constraints.

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Allocate uses dynamic programming (DP) to solve optimization problem which can be  defined as sequential decision processes. DP is not restricted by any requirement of linearity, convexity or even continuity, making it specially suitable for this kind of problems. The feasible numerical space is divided in a number of discretization points. The algorithm evaluates the objective function for each point and selects the best possible combination of load for each generating unit that maximize the objective function (total hydropower station output) or minimize the objective function (total amount of water released to produce fixed amount of hydropower station power) for a given reservoir level.

In order to improve the accuracy of the model results a two step seamless process is adopted. The first step produces a near optimal solution. In the second step the previous operating policy is further refined, until the optimal one that maximizes / minimizes the objective function, is obtained.

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Numerous constraints can be specified and applied during the optimization process:
User can click select and change input parameters, add or remove available generating units or set important constraints. After saving Allocate reads the parameters and auto configures to solve the optimization problem with the selected inputs.
After the run the optimal or best possible results are presented to the user of the program. Those results can be applied to the real system immediately via the post processing interface.
 
Here is the list of possible parameters and constraints that the end user of Allocate can modify:

  • Availability of the generating units from previous time step
  • Startup costs
  • Gate and generator constraints
  • Rough zones
  • Other specific to the local implementation

Allocate optimization can benefit the hydropower systems owners and operators by increasing system output by more than 2%.

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Allocate can be setup to solve two optimization problems:

1, Find the maximum power station output (cumecs) , combining the power of each available generating unit in such a way that the total hydropower station discharge is mimimal.

2, Given the fixed amount of powerstation discharge find the maximum powerstation output (MW) by combining the power of each available generating unit.

Allocate uses Dynamic Programming techniques to solve the problems very efficiently and with very high accuracy. The first optimization problem can be solved by iterations, varying the station discharge and calculating the power station output to mach the required power output. The results are optimal or best possible given the input data and the system constraints.

The second optimization problem can be solved with a single run (the run takes les than 10 seconds in most cases) and the results will be the optimal or best possible given the inputs and the system constraints.

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The flow chart of the Allocate's problem formulation is depicted below. Allocate is very flexible to end users requirements allowing the end user to formulate different problems for different power stations.

  1. Number of the available generating units up to 8 unit of different size and type can be formulated.
  2. Can have common or separate hydraulic conduits with specific hydraulic characteristics for each.
  3. Can define a common tail water for the power station
  4. For each generating unit can define efficiency tables for range of possible Q and H combination
  5. Can specify rough zones and non feasible areas on the Q,H diagrams.

The schematic diagrams of most of the available options is shown above. After the data is entered Allocate will create a project file which will be saved in Allocate projects folder. Many projects can be formulated and saved in the projects folder.

The main menu of Allocate is shown bellow.

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To run Allocate user selects the project which loads into the Allocate environment, then selects two parameters, the reservoir level and the power station discharge. In a mater of seconds Allocate calculates the optimal results for each generating unit.

Generating units can be excluded from the problem by simply clicking the check box in front of the unit (unit is off line for maintenance)

The hydraulic loss function for each power conduit can be defined for each generating unit from this dialog.

If common conduit then the user selects the check box Common conduit and defines the hydraulic losses for this case.

The tail water function can be defined as well.

The user can use this dialog to specify a minimum station discharge that has to be maintained for each generating unit.

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The results from the optimization are saved to a text file and can easily interfaced with SCADA or other system. In Allocate the results are shown to the end user in the following dialog.

In addition same results can be displayed in analog meters gauges. Intraweb or web interface can be developed as  additional user interface to the output results.

Allocate can run in a loop mode for a range of power station discharges and a range of reservoir levels. The results are saved in an excel like table with details for each cell (discharge, reservoir level) as shown on the following picture.

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