Hydro Shaping Logic
Aurora provides a very flexible algorithm for hourly shaping of hydro generation. Project energies and shaping constraints can be specified at any level of unit aggregation. This provides the ability to easily produce a generation pattern that is representative for all hydro resources in an area or zone, without having to specify detailed information on generation patterns for each individual project. It is also straightforward to create a unique hydro set for a particular project or small set of projects where more differentiation on specific unit generation patterns is needed. Unique hydro datasets are specified as different records (unique column names) in the Hydro Vectors table and Hydro Monthly tables.
The input objects that hold the data pertinent to the hydro shaping logic are referred to as hydro sets. Each hydro project has a pointer to one of these hydro sets. Each hydro set has factors defining annual and monthly energy production, and hourly shaping parameters consisting of a target shaping factor, and constraints for instantaneous minimum, instantaneous maximum, and a sustained maximum.
Each hydro set requires defining a demand set to use in the shaping calculations. The demand sets are defined in the Shape Areas field of the Hydro Vectors table. The demand set can consist of a single area, a user-defined comma separated set of areas, a demand collection, or a system-wide demand by entering the “System” keyword. The shaping factor and demand set are used to produce a target shape for hourly generation. The shaping algorithm attempts to meet this generation pattern in aggregate for all the units in a hydro set, subject to available energy and shaping constraints.
The model performs most of the hydro shaping calculations at the beginning of each month. The logic works as follows for each hydro set:
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The average demand for the month and the average daily demand for each day of the month is found for the areas specified in the demand set.
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Using the input annual and monthly energy factors, the average hydro energy for the previous month, current month, and next month is calculated for all hydro units in the hydro set.
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A linear smoothing algorithm is used to produce a normalized daily average generation pattern with continuous transitions across month boundaries. This prevents any large step change in generation as the model moves from the end of one month to the start of the next. This pattern is then combined with the average daily demand pattern calculated in step 1 to produce average daily hydro energies for each day of the month.
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Then for each day of the month, Aurora uses the following process to produce the hourly hydro generation pattern:
- A target hourly shape for the 24-hour period is calculated using the shaping factor and the following formula:
Target Hourly Hydro Shape = (1 + shape factor * (hourly demand – average daily demand)/average daily hydro energy) * monthly energy factor * annual energy factor.
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A feasibility check is made against the instantaneous minimums and maximums specified for the hydro set. If the minimum can not be met due to insufficient energy, or the maximum due to excess energy, the binding constraint will be relaxed to allow the correct energy production for the day.
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A check is done across the day against the instantaneous maximum and minimums. If there are any violations, the excess, or underage, is spread or taken evenly from the other hours if possible.
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A check is done against the sustained maximum. Any violation is once again spread evenly to the other hours and the algorithm loops back to the maximum and minimum checks.
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If the constraints cannot be satisfied, Aurora will change the input shaping constraints to an instantaneous maximum=1, instantaneous minimum=0, and a sustained maximum=1 and will modify the formula to use average daily demand in the denominator. This is a pattern that by definition can be met, and essentially causes the projects in the hydro set to do proportionate load following, instead of attempting to produce a target residual load. Aurora will then generate a message informing the user that this has occurred.
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Shaping logic for hydro and energy storage resources can be bypassed by using a weekly vector as a time-series input. Storage shaping and hydro energy shaping can be forced by manual input. See Hourly Shaping Factor for the steps on how to do this.
When specified, ramp rates are only taken into account when there is exactly one resource in the hydro set. Otherwise, ramp rates will only be honored if Use Daily Optimization in the Hydro Vectors table is set to True.
NOTE: We added a Daily Maximum column to Hydro Vectors input table to set the maximum average capacity factor over each day in the hydro scheduling logic.
Hydro Shaping Logic
