Power system operations and control: Difference between revisions

Revision as of 06:08, 30 May 2022

Revision as of 06:18, 30 May 2022

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| title=Dispatch curve

| yZero= | xAxis=Demand (MW) | yAxis=Cost ($/MWh) | yMax= | yGrid=y | width= | legend=-

| vAnnotationsValues={"text": "PredictedExpected demand", "x": 150}

| hAnnotationsValues={"text": "System lambda", "y": 60}

| hideSource=true

| right

}}

The decisions ("[[economic dispatch]]") are based on the '''dispatch curve''', where the X-axis constitutes the system power, intervals for the generation units are placed on this axis in the ''[[merit order]]'' with the interval length corresponding to the maximum power of the unit, Y-axis values represent the marginal cost (per-[[MWh]] of electricity, ignoring the startup costs). For cost-based decisions, the units are sorted by increasing marginal cost. The graph on the right describes an extremely simplified system, with three committed generator units (fully dispatchable, with constant per-MWh cost):<ref name=psu/>

* A can deliver up to 120 MW at the cost of $30 per MWh (from 0 to 120 MW of system power);

* B can deliver up to 80 MW at $60/MWh (from 120 to 200 MW of system power);

* C is capable of 50 MW at $120/MWh (from 200 to 250 MW of system power).

At the expected demand is 150 MW (a vertical line on the graph), unit A will be engaged at full 120 MW power, unit B - at 30 MW power, unit C will be kept in reserve. The area under the dispatch curve to the left of this line represents the cost per hour of operation (ignoring the startup costs, $30 * 120 + $60 * 30 = 5,400), the incremental cost of the next MWh of electricity ($60 in the example, represented by a horizontal line on the graph) is called '''system lambda''' (thus another name for the curve, ''system lambda curve'')

== Minutes-ahead operation ==